The Full Wiki

More info on String theory

String theory: Wikis

  
  
  

Encyclopedia

From Wikipedia, the free encyclopedia

String theory
Calabi-Yau-alternate.png
Superstring theory
Theory
String theory
Superstrings
Bosonic string theory
M-theory (simplified)
Type I string · Type II string
Heterotic string
String field theory
Holographic principle
.String theory is a developing branch of quantum mechanics and general relativity with the aim of merging and reconciling the two areas of physics into a quantum theory of gravity.^ String theory is a promising approach to a consistent quantum theory of gravity.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ This is where string theory comes into the picture.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ This was the earliest indication that string theory incorporated general relativity.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

[1] .The strings of string theory are one-dimensional oscillating lines, but they are no longer considered fundamental to the theory, which can be formulated in terms of points or surfaces too.^ The Strings of string theory are one-dimensional oscillating lines, but they are no longer considered fundamental to the theory, which can be formulated in terms of points or surfaces too.
  • SFCCO | FREE FOR ALL, (but for you $15) 28 January 2010 0:56 UTC www.sfcco.org [Source type: General]

^ String theory starts with the idea that fundamental particles are not point-like but excitations of a one-dimensional string.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ According to string theory, absolutely everything in the universeall of the particles that make up matter and forcesis comprised of tiny vibrating fundamental strings.
  • SFCCO | FREE FOR ALL, (but for you $15) 28 January 2010 0:56 UTC www.sfcco.org [Source type: General]

.Since its inception as the dual resonance model which described the strongly interacting hadrons as strings, the term string theory has changed to include any of a group of related superstring theories which unite them.^ In string theory, we use the sigma model which describes test strings.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ Thus string theory incorporates two major changes to the spacetime of general relativity that were proposed long before string theory became popular in the mid-1980s.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ The Strings of string theory are one-dimensional oscillating lines, but they are no longer considered fundamental to the theory, which can be formulated in terms of points or surfaces too.
  • SFCCO | FREE FOR ALL, (but for you $15) 28 January 2010 0:56 UTC www.sfcco.org [Source type: General]

.One shared property of all these theories is the holographic principle.^ But both of these theories are (in principle) defined for all values of the coupling.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ The combination of all these theories makes up a single large theory called the "Standard Model" of particle interactions, which is a quantum gauge theory.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ Yet all these theories are fundamentally flawed because they still regard strings as moving in a fixed, background space-time.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

.String theory itself comes in many different formulations, each one with a different mathematical structure, and each best describing different physical circumstances.^ This is where string theory comes into the picture.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ Elegant mathematics of string theory .
  • Universal Theory - Super String Theory 28 January 2010 0:56 UTC www.universaltheory.org [Source type: FILTERED WITH BAYES]

^ Neil Turok from the Perimeter institute announced that mathematical tools emerged from String theory suggest that in some situations space may be an illusion.
  • Universal Theory - Super String Theory 28 January 2010 0:56 UTC www.universaltheory.org [Source type: FILTERED WITH BAYES]

.But the principles shared by these approaches, their mutual logical consistency, and the fact that some of them easily include the standard model of particle physics, has led many of the world's greatest living physicists (such as Edward Witten, Juan Maldacena and Leonard Susskind) to believe that the string theory is a step towards the correct fundamental description of nature.^ Particles & Strings - an overview of the frontier of particle physics and string theory.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ String theory is a promising approach to a consistent quantum theory of gravity.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ There are other approaches to nonperturbative string theory such as string field theory.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

.In particular, string theory is the first candidate for the theory of everything (TOE), a way to describe the known fundamental forces (gravitational, electromagnetic, weak and strong interactions) and matter (quarks and leptons) in a mathematically complete system.^ Quantum field theory, then, is a mathematical framework to describe interactions among force carriers and matter particles.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ The electromagnetic and weak forces interact with matter according to their hyper-charge and weak charge, which make this pattern.
  • Garrett Lisi on his theory of everything | Video on TED.com 28 January 2010 0:56 UTC www.ted.com [Source type: FILTERED WITH BAYES]

^ The Strings of string theory are one-dimensional oscillating lines, but they are no longer considered fundamental to the theory, which can be formulated in terms of points or surfaces too.
  • SFCCO | FREE FOR ALL, (but for you $15) 28 January 2010 0:56 UTC www.sfcco.org [Source type: General]

.Many prominent physicists, such as Richard Feynman and Sheldon Lee Glashow have criticized string theory for not providing any quantitative experimental predictions.^ Many physicists think this is a weakness of the theory, but Leonard Susskind thinks it could actually help us understand why our universe is so well suited to life.
  • String theory: A beginner's guide - physics-math - 15 April 2009 - New Scientist 28 January 2010 0:56 UTC www.newscientist.com [Source type: FILTERED WITH BAYES]

^ In 1974 John Schwartz and Joel Schrek claimed that a mass-less spin-2 particle that is predicted by string theory is the long sought and never found graviton.
  • Universal Theory - Super String Theory 28 January 2010 0:56 UTC www.universaltheory.org [Source type: FILTERED WITH BAYES]

^ String theory, also known by names such as "superstring theory" and sometimes "M-theory", is an idea that has been around for a rather long time, over two decades.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

[2] .[3] Like any other quantum theory of gravity, it is widely believed that testing the theory directly would require prohibitively expensive feats of engineering.^ I would like to communicate with you directly.
  • String Theory, the Universe and God. Bear with me. | SciGuy | Chron.com - Houston Chronicle 28 January 2010 0:56 UTC blogs.chron.com [Source type: Original source]

^ I would like to communicate with you directly."
  • String Theory, the Universe and God. Bear with me. | SciGuy | Chron.com - Houston Chronicle 28 January 2010 0:56 UTC blogs.chron.com [Source type: Original source]

^ This theory and others like it are long shots.
  • Garrett Lisi on his theory of everything | Video on TED.com 28 January 2010 0:56 UTC www.ted.com [Source type: FILTERED WITH BAYES]

.Whether there are stringent indirect tests of the theory is unknown.^ And there's plenty of string theorists beavering away trying to come up with other ways to test string theory, so it's certainly recognized as a priority in that community.
  • Evidence for String Theory!! - JREF Forum 28 January 2010 0:56 UTC forums.randi.org [Source type: FILTERED WITH BAYES]

^ There is another test one can perform with the gauge theory at finite temperature.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ In another two or three years it should be much clearer whether there is a detailed, consistent and tractable scenario to connect string theory to the real world.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

.String theory is of interest to many physicists because it requires new mathematical and physical ideas to mesh together its very different mathematical formulations.^ String Theory for news .
  • KVR: Ugo String Theory - Virtual Instrument 28 January 2010 0:56 UTC www.kvraudio.com [Source type: General]

^ It was certainly an interesting new mathematical problem in a physical context.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ The Strings of string theory are one-dimensional oscillating lines, but they are no longer considered fundamental to the theory, which can be formulated in terms of points or surfaces too.
  • SFCCO | FREE FOR ALL, (but for you $15) 28 January 2010 0:56 UTC www.sfcco.org [Source type: General]

.One of the most inclusive of these is the 11-dimensional M-theory, which requires spacetime to have eleven dimensions,[4] as opposed to the usual three spatial dimensions and the fourth dimension of time.^ Relativity added time as a fourth dimension to Newton's three dimensions.
  • Classical Physics, Quantum Mechanics, Relativity, Super String Theory And Mediation 28 January 2010 0:56 UTC mediate.com [Source type: FILTERED WITH BAYES]

^ But again, time is different from the three spatial dimensions.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ Ergo, the fourth dimension is expanding relative to the three spatial dimensions.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

.The original string theories from the 1980s describe special cases of M-theory where the eleventh dimension is a very small circle or a line, and if these formulations are considered as fundamental, then string theory requires ten dimensions.^ The Strings of string theory are one-dimensional oscillating lines, but they are no longer considered fundamental to the theory, which can be formulated in terms of points or surfaces too.
  • SFCCO | FREE FOR ALL, (but for you $15) 28 January 2010 0:56 UTC www.sfcco.org [Source type: General]

^ According to string theory, absolutely everything in the universeall of the particles that make up matter and forcesis comprised of tiny vibrating fundamental strings.
  • SFCCO | FREE FOR ALL, (but for you $15) 28 January 2010 0:56 UTC www.sfcco.org [Source type: General]

^ But most of what I DO know about string theory originally came from the NOVA series "The Elegant Universe".
  • xkcd • View topic - "String Theory" Discussion 28 January 2010 0:56 UTC forums.xkcd.com [Source type: General]

.But the theory also describes universes like ours, with four observable spacetime dimensions, as well as universes with up to 10 flat space dimensions, and also cases where the position in some of the dimensions is not described by a real number, but by a completely different type of mathematical quantity.^ Finally, we are in the wrong number of spacetime dimensions -- 10 rather than 4.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ Like the type I string, both the heterotic string theories are parity-violating in 10 dimensions.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ This superstring is consistent in 10 spacetime dimensions.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

.So the notion of spacetime dimension is not fixed in string theory: it is best thought of as different in different circumstances.^ Spacetime in string theory .
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ Oh and different parts of string theory have different numbers of dimensions.
  • xkcd • View topic - "String Theory" Discussion 28 January 2010 0:56 UTC forums.xkcd.com [Source type: General]

^ So, for a string in flat spacetime, c is the spacetime dimension.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

[5]
.String theories include objects more general than strings, called branes.^ Likewise the D1-brane is also called a D-string.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ It is called the bosonic string theory .
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ But this is SO much more than a string modeler.
  • KVR: Ugo String Theory - Virtual Instrument 28 January 2010 0:56 UTC www.kvraudio.com [Source type: General]

.The word brane, derived from "membrane", refers to a variety of interrelated objects, such as D-branes, black p-branes and Neveu-Schwarz 5-branes.^ Furthermore, M-theory indicates that the "true home" of the theory may actually be the eleventh dimension, where we find new, exotic objects, such as super membranes and 5-branes.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ A p-brane expanding infinitely far in some spatial directions can act as black hole in the remaining dimensions, trapping objects that come too close.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

.These are extended objects that are charged sources for differential form generalizations of the vector potential electromagnetic field.^ These D-branes are also sources for the p -form fields F p .
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ The answer turns out to be beautifully simple: objects carrying charge under second-rank tensor fields are strings .
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ The most intriguing property of CSL-1 is that the object is clearly extended and the isophotes of the two sources show no distortion at all.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

.These objects are related to one another by a variety of dualities.^ Venn diagrams are used to represent classes of objects, and they can also assist us in reasoning about the relations between these classes.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ So one would never see these objects in perturbation theory in g s .
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ Secondly, general relativity demonstrates that massive objects warp space-time, meaning that as a massive object moves though space-time, it stretches space-time, showing again that space-time in one area can move, or deform, relative to space-time in another area.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

.Black hole-like black p-branes are identified with D-branes, which are endpoints for strings, and this identification is called Gauge-gravity duality.^ Likewise the D1-brane is also called a D-string.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ According to string theorists we are most likely living in a D3-brane with six dimensions tightly rolled up.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ In remarks to an American Physical Society newsletter, physicist Frank Wilczek of MIT called the black hole study a sound way to test an unattractive idea.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

.Research on this equivalence has led to new insights on quantum chromodynamics, the fundamental theory of the strong nuclear force.^ However, Tutte’s rich and beautiful theory and methods are important in mathematics and quite fundamental in quantum gravity.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ Quantum field theory, then, is a mathematical framework to describe interactions among force carriers and matter particles.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ In a fundamental theory with no deeper explanation, why should there be such a profusion of fundamental forces and matter particles?
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

[6][7][8][9]

Contents

Overview

.String theory posits that the electrons and quarks within an atom are not 0-dimensional objects, but 1-dimensional strings.^ The Strings of string theory are one-dimensional oscillating lines, but they are no longer considered fundamental to the theory, which can be formulated in terms of points or surfaces too.
  • SFCCO | FREE FOR ALL, (but for you $15) 28 January 2010 0:56 UTC www.sfcco.org [Source type: General]

^ Although superstrings are formulated in a ten-dimensional space-time, in another sense a string field is also a theory about two-dimensional surfaces.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ So the dynamics of the string is described by a two-dimensional theory describing how this worldsheet moves in spacetime.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

.These strings can move and vibrate, giving the observed particles their flavor, charge, mass and spin.^ According to string theory, absolutely everything in the universeall of the particles that make up matter and forcesis comprised of tiny vibrating fundamental strings.
  • SFCCO | FREE FOR ALL, (but for you $15) 28 January 2010 0:56 UTC www.sfcco.org [Source type: General]

^ There are fermionic matter particles, but in the absence of force carriers of the usual type, these cannot carry charges.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ By changing a sign (of a left moving U (1) charge) in the sigma model, one changes its interpretation from a string moving on K to a string moving on a geometrically and topologically different space, called the mirror of K .
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

.The strings make closed loops unless they encounter surfaces, called D-branes, where they can open up into 1-dimensional lines.^ There are also closed strings away from the brane.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ The Strings of string theory are one-dimensional oscillating lines, but they are no longer considered fundamental to the theory, which can be formulated in terms of points or surfaces too.
  • SFCCO | FREE FOR ALL, (but for you $15) 28 January 2010 0:56 UTC www.sfcco.org [Source type: General]

^ According to string theory, absolutely everything in the universeall of the particles that make up matter and forcesis comprised of tiny vibrating fundamental strings.
  • SFCCO | FREE FOR ALL, (but for you $15) 28 January 2010 0:56 UTC www.sfcco.org [Source type: General]

.The endpoints of the string cannot break off the D-brane, but they can slide around on it.^ These open strings move freely along the brane but cannot leave the brane unless the endpoints join and form a closed string.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ The Dirichlet branes are special precisely because they are defined through fundamental strings that end on them.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ Note that among other things, D-branes provide an explanation of the role of the exotic tensor gauge fields in type II string theories: they endow the branes with stability.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

Levels of magnification:
1. Macroscopic level - Matter
2. Molecular level
3. Atomic level - Protons, neutrons, and electrons
4. Subatomic level - Electron
5. Subatomic level - Quarks
6. String level
.Since the string theory is widely believed to be a consistent theory of quantum gravity, many hope that it correctly describes our universe, making it a theory of everything.^ String theory is a promising approach to a consistent quantum theory of gravity.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ It concerns string theory, the universe and God.
  • String Theory, the Universe and God. Bear with me. | SciGuy | Chron.com - Houston Chronicle 28 January 2010 0:56 UTC blogs.chron.com [Source type: Original source]

^ Now it is interpreted as a natural incorporation of gravity with the quantum theory of string.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

.There are known configurations which describe all the observed fundamental forces and matter but with a zero cosmological constant and some new fields.^ There are fermionic matter particles, but in the absence of force carriers of the usual type, these cannot carry charges.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ Quantum field theory, then, is a mathematical framework to describe interactions among force carriers and matter particles.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ These new boundary conditions require that the matter fields are nonzero, so AdS is no longer a solution.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

[10] .There are other configurations with different values of the cosmological constant, which are metastable but long-lived.^ We do this as we have lived with this person so long that we automatically reproduce certain things that were said to us, or treat others as we might have been treated.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ In superstring theory, as long as supersymmetry is unbroken, the cosmological constant is identically zero due to cancelling contributions from bosons and fermions.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ There may be other layers of "information" which differ between different genes, but you can't measure them without an equation.
  • Recursivity: Stephen Meyer's Bogus Information Theory 28 January 2010 0:56 UTC recursed.blogspot.com [Source type: FILTERED WITH BAYES]

.This leads many to believe that there is at least one metastable solution which is quantitatively identical with the standard model, with a small cosmological constant, which contains dark matter and a plausible mechanism for cosmic inflation.^ We punch in the probability of this reference of quantum perception with cosmological data and if 13.7 billions years could be contained in the model, then what says the limit of this universe could not be contained in what this universe might have become?
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ In the case of positive cosmological constant one gets a purely quantum mechanical derivation of the N bound conjectured by Fishler and Banks, see hep-th/0209079.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ I have always intuitively believed that our perspective of space (spacetime) is only one of many, that our universe could be subatomic in someone else’s reality and vice versa.
  • Year help: Could string theory validate many things currently deemed “supernatural”? - Help.com 28 January 2010 0:56 UTC help.com [Source type: General]

.It is not yet known whether string theory has such a solution, nor how much freedom the theory allows to choose the details.^ It is not known whether this is a complete set of solutions.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ String theory, also known by names such as "superstring theory" and sometimes "M-theory", is an idea that has been around for a rather long time, over two decades.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ So the dynamics of the string is described by a two-dimensional theory describing how this worldsheet moves in spacetime.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

.The full theory does not yet have a satisfactory definition in all circumstances, since the scattering of strings is most straightforwardly defined by a perturbation theory.^ One thus has the confusing situation that a two-dimensional CFT describes perturbative string excitations about this space, and a different two-dimensional CFT describes the entire theory.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ I like your standards Claus, but since they're all of the double variety, I always have to address them twice, hence my repeat of the question of 'Is there actual evidence for string theory?'
  • Evidence for String Theory!! - JREF Forum 28 January 2010 0:56 UTC forums.randi.org [Source type: FILTERED WITH BAYES]

^ So let me put this question to the experts: does either string theory or LQG suggest what the connection should be between entropy and the non-expansion of light rays?
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.The complete quantum mechanics of high dimensional branes is not easily defined, and the behavior of string theory in cosmological settings (time-dependent backgrounds) is not fully worked out.^ It has been shown that when this happens, string theory remains completely well defined.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ The Strings of string theory are one-dimensional oscillating lines, but they are no longer considered fundamental to the theory, which can be formulated in terms of points or surfaces too.
  • SFCCO | FREE FOR ALL, (but for you $15) 28 January 2010 0:56 UTC www.sfcco.org [Source type: General]

^ Instead, if you try to define string theory in the wrong dimension, the resulting disease is called “the conformal anomaly”.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.It is also not clear if there is any principle by which string theory selects its vacuum state, the spacetime configuration which determines the properties of our Universe (see string theory landscape).^ Spacetime in string theory .
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ Thus we see that string theories are not just theories of strings.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ It concerns string theory, the universe and God.
  • String Theory, the Universe and God. Bear with me. | SciGuy | Chron.com - Houston Chronicle 28 January 2010 0:56 UTC blogs.chron.com [Source type: Original source]

Basic properties

.String theory can be formulated in terms of an action principle, either the Nambu-Goto action or the Polyakov action, which describes how strings move through space and time.^ So the dynamics of the string is described by a two-dimensional theory describing how this worldsheet moves in spacetime.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ How could an ordinary field theory describe all of string theory?
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ Riemann surface theory is relevant to describing the behavior of strings as they move through space-time.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

.In the absence of external interactions, string dynamics are governed by tension and kinetic energy, which combine to produce oscillations.^ To if distanciar of the elementary school, the secondary one goes to produce its proper dynamics, goes to give to beginning the tertiary ones that its energy and maser will initiate its in agreement translation.
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ Instead of a coupling constant, all string theories have a scalar particle which governs the strength of the interactions.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ With this, the displayed one is confirmed until, of that astros small they possess little irregular dynamics and orbits, for produces little energy, and this here independe of the distancia of the Sun.
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

.The quantum mechanics of strings implies these oscillations take on discrete vibrational modes, the spectrum of the theory.^ I don't claim to understand either String Theory or quantum mechanics well enough to speak authoritatively, but my impression is that the "extra" dimensions are necessary because the vibrational patterns in systems of lower dimensions aren't complex enough to model the forces of the physical world.
  • Evidence for String Theory!! - JREF Forum 28 January 2010 0:56 UTC forums.randi.org [Source type: FILTERED WITH BAYES]

^ The Strings of string theory are one-dimensional oscillating lines, but they are no longer considered fundamental to the theory, which can be formulated in terms of points or surfaces too.
  • SFCCO | FREE FOR ALL, (but for you $15) 28 January 2010 0:56 UTC www.sfcco.org [Source type: General]

^ According to string theory, absolutely everything in the universeall of the particles that make up matter and forcesis comprised of tiny vibrating fundamental strings.
  • SFCCO | FREE FOR ALL, (but for you $15) 28 January 2010 0:56 UTC www.sfcco.org [Source type: General]

.On distance scales larger than the string radius, each oscillation mode behaves as a different species of particle, with its mass, spin and charge determined by the string's dynamics.^ The oscillations of the string imbue it with characteristics such as mass and charge.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ The proposed "strings" are of an order of magnitude so much smaller than individual atoms or even subatomic particles that we'd need an entirely new toolset to do so.
  • Evidence for String Theory!! - JREF Forum 28 January 2010 0:56 UTC forums.randi.org [Source type: FILTERED WITH BAYES]

^ By changing a sign (of a left moving U (1) charge) in the sigma model, one changes its interpretation from a string moving on K to a string moving on a geometrically and topologically different space, called the mirror of K .
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

.Splitting and recombination of strings correspond to particle emission and absorption, giving rise to the interactions between particles.^ Instead of a coupling constant, all string theories have a scalar particle which governs the strength of the interactions.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ Non-perturbation Theory - Interactions in superstring theory are expressed in terms of the splitting and joining of strings (see Figure 14 and 15).
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ While the diagrams describing the scattering of point particles have definite points where a particle splits into two particles, the corresponding diagrams for string scattering are completely smooth (Figure 3).
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

.An analogy for strings' modes of vibration is a guitar string's production of multiple but distinct musical notes.^ Note 2 If one quantizes a free relativistic (super)string in flat spacetime, one finds an infinite tower of modes of increasing mass.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ The various modes of vibration of these minimal surfaces are then quantized to produce string wave function.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

In the analogy, different notes correspond to different particles. .The only difference is the guitar is only 2-dimensional, you can strum it up, and down.^ Of course, they hope that they aren't building up an edifice which is all going to be knocked down; but right now you, and everyone else, is right to be sceptical.
  • Evidence for String Theory!! - JREF Forum 28 January 2010 0:56 UTC forums.randi.org [Source type: FILTERED WITH BAYES]

^ We can move up and down, back and forth, in space; but only ever forwards in time.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ Of course, you are entitled to count only the different ways the spin networks cross the boundary of a region, but that strikes me as answer analysis… .
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.In actuality the guitar strings would be every dimension, and the strings could vibrate in any direction.^ Following the development of quantum theory, the next step would be to generate, out of the wave functions for individual string vibrations, a super wave function for the string field.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ However, almost all the code I've ever seen that indexes into strings is actually iterating through strings (or using APIs that return indexes into strings, which could just as easily use iterators).

^ Large Dimensions - Since the Planck length is the natural scale of strings, the most probable universe would be the one in which all of the dimensions are comparable to the Planck length.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

.Meaning that the particles could move through not only our dimension, but other dimensions as well.^ All particles will have a probability of being caught in the fourth expanding dimension in proportion to their energy, and thus there is a probability that the particles will move in a manner that approximates the expanding surfaces of the fourth dimension.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ In other words, all the observed particles (quarks, leptons, gauge bosons, etc) are confined to move on the brane and only gravity exists in the bulk since the graviton comes from closed strings.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ I have the feeling that non-renormalizability is not the only way to describe the diseases of string theory in dimensions other than 10 or 26.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.String theory includes both open strings, which have two distinct endpoints, and closed strings making a complete loop.^ This type contains both open and closed strings.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ The string could be closed, like a loop, or open, with two end points (Figure 2).
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ A string can be either open, with two end-points, or closed, like a loop.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

.The two types of string behave in slightly different ways, yielding two different spectra.^ One thus has the confusing situation that a two-dimensional CFT describes perturbative string excitations about this space, and a different two-dimensional CFT describes the entire theory.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ The beauty of the theory is that one type of thing—namely a string—can vibrate in different ways and give you different types of particles.
  • The Complete Idiot's Guide to String Theory: Scientific American Podcast 28 January 2010 0:56 UTC www.scientificamerican.com [Source type: Original source]

^ These two theories certainly look different at weak coupling, but a crucial aspect of this correspondence is that when the string theory is weakly coupled, the gauge theory is strongly coupled and vice versa.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

.For example, in most string theories, one of the closed string modes is the graviton, and one of the open string modes is the photon.^ SO(32) Heterotic - This is a theory of closed string.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ Thus there can be theories with only closed strings and no open strings.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ The Strings of string theory are one-dimensional oscillating lines, but they are no longer considered fundamental to the theory, which can be formulated in terms of points or surfaces too.
  • SFCCO | FREE FOR ALL, (but for you $15) 28 January 2010 0:56 UTC www.sfcco.org [Source type: General]

.Because the two ends of an open string can always meet and connect, forming a closed string, there are no string theories without closed strings.^ For a closed string it takes the form: .
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ But because of supersymmetry, there is no tachyon.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ That's because the graviton is a closed string - a string with no ends would not be stuck to the brane at all.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

.The earliest string model, the bosonic string, incorporated only bosons.^ Another consequence of the fact that strings see the spacetime only through the sigma model is that spacetimes which are singular in general relativity can be completely nonsingular in string theory.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ This was the earliest indication that string theory incorporated general relativity.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ Since the string only senses the spacetime through this sigma model, two metrics that yield the same sigma model are indistinguishable in string theory.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

.This model describes, in low enough energies, a quantum gravity theory, which also includes (if open strings are incorporated as well) gauge fields such as the photon (or, more generally, any gauge theory).^ String theory is a promising approach to a consistent quantum theory of gravity.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ There are other approaches to nonperturbative string theory such as string field theory.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ There are open strings on the brane whose low-energy modes are described by a U ( N ) gauge theory.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

However, this model has problems. .Most importantly, the theory has a fundamental instability, believed to result in the decay (at least partially) of spacetime itself.^ I want to focus on the more fundamental changes in spacetime that arise from string theory.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ S Duality - S-duality can be examined most easily in Type II string theory, because this theory happens to be S-dual to itself.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ So whoever said that evidently believes that, since an infinite universe leads to nonsensical conclusions, a good fundamental theory must *not* allow such a thing.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.Additionally, as the name implies, the spectrum of particles contains only bosons, particles which, like the photon, obey particular rules of behavior.^ This contrasts unfavourably with reality -- the only exactly massless particles in the world, so far as we know, are the photon and the graviton.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ The essence of any theory of quantum gravityis that there exists a particle called the graviton which is a quantum of gravity, just like the photon which is a quantum of light.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ Its spectrum of particle-like excitations includes one particle whose mass is an imaginary number -- a "tachyon", generally believed to be an unphysical object.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

.Roughly speaking, bosons are the constituents of radiation, but not of matter, which is made of fermions.^ As we have seen above, bosons tend to be the mediators of fundamental forces, while fermions make up the "matter" which experiences these forces.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ Supersymmetry is usually described as a symmetry between bosons and fermions, but it is much more than just another symmetry of matter.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

.Investigating how a string theory may include fermions in its spectrum led to the invention of supersymmetry, a mathematical relation between bosons and fermions.^ It is called the bosonic string theory .
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ Fraser: Isn't that one of the thoughts that (it goes back to string theory), that gravity is so weak because it is moving between multiple dimensions?
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ In our view, the connection between quantum system engineering and string theory conceptually resembles the connection between Green functions and field theory (see, e.g.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.String theories which include fermionic vibrations are now known as superstring theories; several different kinds have been described, but all are now thought to be different limits of M-theory.^ How could an ordinary field theory describe all of string theory?
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ Note2 By now, there are several excellent textbooks on string theory, e.g.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ According to string theory, absolutely everything in the universeall of the particles that make up matter and forcesis comprised of tiny vibrating fundamental strings.
  • SFCCO | FREE FOR ALL, (but for you $15) 28 January 2010 0:56 UTC www.sfcco.org [Source type: General]

.Some qualitative properties of quantum strings can be understood in a fairly simple fashion.^ This is a beautiful property because it suggests that the strength of string interactions could in some way be self-consistently determined by the theory instead of being an experimental input.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ Because B is present in all string theories, one may suspect that it too endows some suitable charged dynamical object with this property of stability.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ A string field theory is therefore about the quantum properties of two-dimensional surfaces.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

.For example, quantum strings have tension, much like regular strings made of twine; this tension is considered a fundamental parameter of the theory.^ The Strings of string theory are one-dimensional oscillating lines, but they are no longer considered fundamental to the theory, which can be formulated in terms of points or surfaces too.
  • SFCCO | FREE FOR ALL, (but for you $15) 28 January 2010 0:56 UTC www.sfcco.org [Source type: General]

^ According to string theory, absolutely everything in the universeall of the particles that make up matter and forcesis comprised of tiny vibrating fundamental strings.
  • SFCCO | FREE FOR ALL, (but for you $15) 28 January 2010 0:56 UTC www.sfcco.org [Source type: General]

^ This is a condition we would like to ask of a truly fundamental theory.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.The tension of a quantum string is closely related to its size.^ A closely related problem in relating string theory to nature is the problem of the "cosmological constant".
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

.Consider a closed loop of string, left to move through space without external forces.^ The other possibilities are an open universe ( ) in which space will expand forever, and a closed universe ( ) in which gravity will halt the expansion and force the universe to contract, eventually leading to a "big crunch".
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ Considering the simple example of a bosonic string with one dimension (for both right and left movers) compactified on a circle, say X 25 in a form similar to Eq.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ By changing a sign (of a left moving U (1) charge) in the sigma model, one changes its interpretation from a string moving on K to a string moving on a geometrically and topologically different space, called the mirror of K .
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

Its tension will tend to contract it into a smaller and smaller loop. Classical intuition suggests that it might shrink to a single point, but this would violate Heisenberg's uncertainty principle. .The characteristic size of the string loop will be a balance between the tension force, acting to make it small, and the uncertainty effect, which keeps it "stretched". Consequently, the minimum size of a string is related to the string tension.^ Hubble: cosmic string verdict by February I just wanted to keep this for inspection, and relate Lubos's current statement in this regard, together, for refreshing look at this topic.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ It is found that inflation can stretch the tiny string to astronomical size (length-wise) and very high density (see cosmic string ).
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ I think it is hard sometimes to keep a global view about all the things that are included in this process, yet at some level, such geometries would have to be explained in relation, between the very small, and the every large.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

World-sheet

.A point-like particle's motion may be described by drawing a graph of its position (in one or two dimensions of space) against time.^ It becomes necessary to assume that this field is not just a number at every point of space and time, but a "quantum operator", having definite but somewhat complicated mathematical properties.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ Although superstrings are formulated in a ten-dimensional space-time, in another sense a string field is also a theory about two-dimensional surfaces.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ When the calculation is done, the critical dimensionality is not four as one may expect (three axes of space and one of time).
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

The resulting picture depicts the worldline of the particle (its 'history') in spacetime. .By analogy, a similar graph depicting the progress of a string as time passes by can be obtained; the string (a one-dimensional object — a small line — by itself) will trace out a surface (a two-dimensional manifold), known as the worldsheet.^ The string sweeps out a worldsheet as varies from one instant to another.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ The string is an one-dimensional object, which can move in various ways.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ A one-dimensional string traces out a two-dimensional worldsheet.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

.The different string modes (representing different particles, such as photon or graviton) are surface waves on this manifold.^ This contrasts unfavourably with reality -- the only exactly massless particles in the world, so far as we know, are the photon and the graviton.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ How can photons display both wave and particle properties?
  • ALL TIED UP & STRUNG ALONG: HOLLYWOOD STRING THEORY MOVIE!!! LOOKING FOR EXTRAS!!! - Physics Forums: Physics, Astronomy, Math, & Philosophy Forums! 28 January 2010 0:56 UTC physicsmathforums.com [Source type: FILTERED WITH BAYES]

^ This graviton-like particle was a great embarrassement when the string was first being developed as a model of hadrons.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

A closed string looks like a small loop, so its worldsheet will look like a pipe or, more generally, a Riemann surface (a two-dimensional oriented manifold) with no boundaries (i.e. no edge). An open string looks like a short line, so its worldsheet will look like a strip or, more generally, a Riemann surface with a boundary.
Interaction in the subatomic world: world lines of point-like particles in the Standard Model or a world sheet swept up by closed strings in string theory
Strings can split and connect. This is reflected by the form of their worldsheet (more accurately, by its topology). .For example, if a closed string splits, its worldsheet will look like a single pipe splitting (or connected) to two pipes (often referred to as a pair of pants — see drawing at right).^ A pair of closed strings can join when any pair of points coincides, to make a single closed string.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ Considering the simple example of a bosonic string with one dimension (for both right and left movers) compactified on a circle, say X 25 in a form similar to Eq.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ It turns out that the most natural prescription leads to a single possible open string theory, called type I superstring theory, and two distinct closed string theories, called type IIA and type IIB string theory.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

.If a closed string splits and its two parts later reconnect, its worldsheet will look like a single pipe splitting to two and then reconnecting, which also looks like a torus connected to two pipes (one representing the ingoing string, and the other — the outgoing one).^ A one-dimensional string traces out a two-dimensional worldsheet.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ For the others, the ratio between the diâmetros diminishes for less of the one than two, then the ratio also enters the removal beats for less of the one than two.
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ So the dynamics of the string is described by a two-dimensional theory describing how this worldsheet moves in spacetime.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

.An open string doing the same thing will have its worldsheet looking like a ring connected to two strips.^ Clearly string theory does not address the same content as theology (i.e., God), so Horgan must be suggesting that the methods of string theorists are like those of theologians.
  • String Theory → Theology : Gene Expression 28 January 2010 0:56 UTC scienceblogs.com [Source type: FILTERED WITH BAYES]

^ However, if the two end-points of a single open string touch, they can join together and make a closed string.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ The two examples in the followings serve to visualize the geometry of the closed and open strings.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

.Note that the process of a string splitting (or strings connecting) is a global process of the worldsheet, not a local one: locally, the worldsheet looks the same everywhere and it is not possible to determine a single point on the worldsheet where the splitting occurs.^ The Strings of string theory are one-dimensional oscillating lines, but they are no longer considered fundamental to the theory, which can be formulated in terms of points or surfaces too.
  • SFCCO | FREE FOR ALL, (but for you $15) 28 January 2010 0:56 UTC www.sfcco.org [Source type: General]

^ Finally, one would have to devise a "quantum mechanics" of strings in analogy with that for point particles.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ However, if the two end-points of a single open string touch, they can join together and make a closed string.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

.Therefore these processes are an integral part of the theory, and are described by the same dynamics that controls the string modes.^ Stan: "The subject was string theory (of which I know nothing)" Eric screwed up mentioning god in the same post."
  • String Theory, the Universe and God. Bear with me. | SciGuy | Chron.com - Houston Chronicle 28 January 2010 0:56 UTC blogs.chron.com [Source type: Original source]

^ In the Type IIA and IIB theory, these Weyl spinors have opposite and same chiralities respectively.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ So the dynamics of the string is described by a two-dimensional theory describing how this worldsheet moves in spacetime.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

.In some string theories(namely, closed strings in Type I and some versions of the bosonic string), strings can split and reconnect in an opposite orientation (as in a Möbius strip or a Klein bottle).^ It is called the bosonic string theory .
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ SO(32) Heterotic - This is a theory of closed string.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ Since Type IIA string starts out with opposite chirality for the movers, now both movers would have the same chirality, i.e., it changes to a Type IIB string.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

.These theories are called unoriented.^ The combination of all these theories makes up a single large theory called the "Standard Model" of particle interactions, which is a quantum gauge theory.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ (Together, all these theories are sometimes called "gauge theories").
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ However, there is a theory that has unified these four forces (Gravitation, Strong Nuclear force, Weak Nuclear force, Electromagnetism) back in 2003 called ECE THEORY. .
  • String Theory, the Universe and God. Bear with me. | SciGuy | Chron.com - Houston Chronicle 28 January 2010 0:56 UTC blogs.chron.com [Source type: Original source]

Formally, the worldsheet in these theories is a non-orientable surface.

Dualities

.Before the 1990s, string theorists believed there were five distinct superstring theories: open type I, closed type I, closed type IIA, closed type IIB, and the two flavors of heterotic string theory (SO(32) and E8×E8)[11].^ It turns out that the most natural prescription leads to a single possible open string theory, called type I superstring theory, and two distinct closed string theories, called type IIA and type IIB string theory.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ This was also true of the type IIB string.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ This type contains both open and closed strings.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

.The thinking was that out of these five candidate theories, only one was the actual correct theory of everything, and that theory was the one whose low energy limit, with ten spacetime dimensions compactified down to four, matched the physics observed in our world today.^ In this version of the theory, it is noted that solutions to the equation RAB = 0 with RAB the five-dimensional Ricci curvature, may be re-expressed so that in four dimensions, these solutions satisfy Einstein's equations Gμν = 8πTμν with the precise form of the Tμν following from the Ricci-flat condition on the five-dimensional space.

^ Now, one of the things that I think goes along with string theory, is talk about multiple dimensions .
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ Thus, the most straightforward way to connect string theory to the real world is to postulate that 6 spatial dimensions form a compact manifold, whose size is so small that we are unable to detect its existence directly with the probes available to us.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

.It is now believed that this picture was incorrect and that the five superstring theories are connected to one another as if they are each a special case of some more fundamental theory (thought to be M-theory).^ The Strings of string theory are one-dimensional oscillating lines, but they are no longer considered fundamental to the theory, which can be formulated in terms of points or surfaces too.
  • SFCCO | FREE FOR ALL, (but for you $15) 28 January 2010 0:56 UTC www.sfcco.org [Source type: General]

^ Although superstrings are formulated in a ten-dimensional space-time, in another sense a string field is also a theory about two-dimensional surfaces.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ Now, one of the things that I think goes along with string theory, is talk about multiple dimensions .
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

.These theories are related by transformations that are called dualities.^ (Together, all these theories are sometimes called "gauge theories").
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ However, there is a theory that has unified these four forces (Gravitation, Strong Nuclear force, Weak Nuclear force, Electromagnetism) back in 2003 called ECE THEORY. .
  • String Theory, the Universe and God. Bear with me. | SciGuy | Chron.com - Houston Chronicle 28 January 2010 0:56 UTC blogs.chron.com [Source type: Original source]

^ This approach has uncovered the role of new symmetries called "dualities" in string theory.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

.If two theories are related by a duality transformation, it means that the first theory can be transformed in some way so that it ends up looking just like the second theory.^ The former is a likely consequence of string theory — maybe even confirmed for some kinds of black holes, although I am not sure — while the latter always seemed inelegant to me.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ In later life he worked very hard to come up with ever more convoluted ways to make the Steady State theory explain the growing evidence.
  • The Big Bang Theory - talk.origins | Google Groups 28 January 2010 0:56 UTC groups.google.com [Source type: FILTERED WITH BAYES]

^ In quantum theory, a field is not just something associated with waves, but is also related to particles by virtue of the well-known wave-particle duality.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

.The two theories are then said to be dual to one another under that kind of transformation.^ Although superstrings are formulated in a ten-dimensional space-time, in another sense a string field is also a theory about two-dimensional surfaces.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ One thus has the confusing situation that a two-dimensional CFT describes perturbative string excitations about this space, and a different two-dimensional CFT describes the entire theory.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ Professor Eugene Herrin, a member of the team, said that two strangelets just one-tenth the breadth of a hair would account for the observations.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

.Put differently, the two theories are mathematically different descriptions of the same phenomena.^ The two theories are mathematically different and cannot be applied simultaneously.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ One thus has the confusing situation that a two-dimensional CFT describes perturbative string excitations about this space, and a different two-dimensional CFT describes the entire theory.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ These two theories certainly look different at weak coupling, but a crucial aspect of this correspondence is that when the string theory is weakly coupled, the gauge theory is strongly coupled and vice versa.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

These dualities link quantities that were also thought to be separate. .Large and small distance scales, as well as strong and weak coupling strengths, are quantities that have always marked very distinct limits of behavior of a physical system in both classical field theory and quantum particle physics.^ Consider an ordinary quantum field theory of pointlike particles.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ Type I string theory is identical to the weak coupling limit of the Heterotic-O theory.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ The classical field theory of electromagnetism breaks down at very short distances, or in the presence of very strong fields.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

.But strings can obscure the difference between large and small, strong and weak, and this is how these five very different theories end up being related.^ Thus we get a connection between a gauge theory at weak coupling, and strings in AdS 5 × S 5 at strong coupling.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ According to string theory, absolutely everything in the universeall of the particles that make up matter and forcesis comprised of tiny vibrating fundamental strings.
  • SFCCO | FREE FOR ALL, (but for you $15) 28 January 2010 0:56 UTC www.sfcco.org [Source type: General]

^ No, it just means that it's a hypothesis, which is interesting in that it's consistent with the present Standard Model and ties up some loose ends theoretically, but still needs to be tested (in this regard, string theory is a misnomer).
  • Evidence for String Theory!! - JREF Forum 28 January 2010 0:56 UTC forums.randi.org [Source type: FILTERED WITH BAYES]

.T-duality relates the large and small distance scales between string theories, whereas S-duality relates strong and weak coupling strengths between string theories.^ U Duality and 11 Dimensions - U-duality is essentially a combination of S-duality and T-duality, e.g., U-duality implies that a theory A which is compactified to small size with weak coupling constant is dual to a theory B which is compactified to large size with strong coupling constant.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ Type I string theory is identical to the weak coupling limit of the Heterotic-O theory.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ Thus we get a connection between a gauge theory at weak coupling, and strings in AdS 5 × S 5 at strong coupling.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

U-duality links T-duality and S-duality.
String theories
Type Spacetime dimensions
Details
Bosonic 26 .Only bosons, no fermions, meaning only forces, no matter, with both open and closed strings; major flaw: a particle with imaginary mass, called the tachyon, representing an instability in the theory.^ This type contains both open and closed strings.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ SO(32) Heterotic - This is a theory of closed string.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ Tachyon also occurs in the super-string theory.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

I 10 Supersymmetry between forces and matter, with both open and closed strings; no tachyon; group symmetry is SO(32)
IIA 10 Supersymmetry between forces and matter, with closed strings and open strings bound to D-branes; no tachyon; massless fermions are non-chiral
IIB 10 Supersymmetry between forces and matter, with closed strings and open strings bound to D-branes; no tachyon; massless fermions are chiral
HO 10 Supersymmetry between forces and matter, with closed strings only; no tachyon; heterotic, meaning right moving and left moving strings differ; group symmetry is SO(32)
HE 10 Supersymmetry between forces and matter, with closed strings only; no tachyon; heterotic, meaning right moving and left moving strings differ; group symmetry is E8×E8
.Note that in the type IIA and type IIB string theories closed strings are allowed to move everywhere throughout the ten-dimensional spacetime (called the bulk), while open strings have their ends attached to D-branes, which are membranes of lower dimensionality (their dimension is odd — 1, 3, 5, 7 or 9 — in type IIA and even — 0, 2, 4, 6 or 8 — in type IIB, including the time direction).^ D-branes for the Type IIA string, and odd dimensional D-branes for the Type IIB string (see Figure 08 ).
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ It is called the bosonic string theory .
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ This type contains both open and closed strings.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

Extra dimensions

Number of dimensions

.An intriguing feature of string theory is that it involves the prediction of extra dimensions.^ Wikipeida reports: http://en.wikipedia.org/wiki/Why_10_dimensions%3F#Number_of_dimensions Number of dimensions One intriguing feature of string theory is that it involves the prediction of extra dimensions.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ Now, one of the things that I think goes along with string theory, is talk about multiple dimensions .
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ The extra 16 left mover dimensions provide the gauge group for the resulting 10-dimensional theory.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

.The number of dimensions is not fixed by any consistency criterion, but flat spacetime solutions do exist in the so-called "critical dimension". Cosmological solutions exist in a wider variety of dimensionalities, and these different dimensions—more precisely different values of the "effective central charge", a count of degrees of freedom which reduces to dimensionality in weakly curved regimes—are related by dynamical transitions.^ The string degrees of freedom X ( , ) trace out a curve as varies at fixed .
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ The number of dimensions is not fixed by any consistency criterion, but flat spacetime solutions do exist in the so-called "critical dimension."
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ Cosmological solutions exist in a wider variety of dimensionalities, and these different dimensions?more precisely different values of the "effective central charge," a count of degrees of freedom which reduces to dimensionality in weakly curved regimes?are related by dynamical transitions.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

[12]
.Nothing in Maxwell's theory of electromagnetism or Einstein's theory of relativity makes this kind of prediction; these theories require physicists to insert the number of dimensions "by hand", and this number is fixed and independent of potential energy.^ Nothing in Maxwell's theory of electromagnetism or Einstein's theory of relativity makes this kind of prediction; these theories require physicists to insert the number of dimensions "by hand," and this number is fixed and independent of potential energy.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ String theory allows one to relate the number of dimensions to scalar potential energy.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ Their proposal only provided a classical framework in which Einstein's gravity and Maxwell's electromagnetism had a common origin (this was hardly their fault, as quantum field theory had not yet been invented at the time!
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

.String theory allows one to relate the number of dimensions to scalar potential energy.^ String theory allows one to relate the number of dimensions to scalar potential energy.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ Now, one of the things that I think goes along with string theory, is talk about multiple dimensions .
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ Considering the simple example of a bosonic string with one dimension (for both right and left movers) compactified on a circle, say X 25 in a form similar to Eq.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

.Technically, this happens because a gauge anomaly exists for every separate number of predicted dimensions, and the gauge anomaly can be counteracted by including nontrivial potential energy into equations to solve motion.^ Technically, this happens because a gauge anomaly exists for every separate number of predicted dimensions, and the gauge anomaly can be counteracted by including nontrivial potential energy into equations to solve motion.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ The field equations are simply d F = 0 and There exists a large class of stationary solutions to ( 3.2 ) which have an SO (4) × SO (4) symmetry, and can be obtained by solving a linear equation.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ There are some theories that are attempting to find ways to make predictions based on multiple dimensions existing.
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

.Furthermore, the absence of potential energy in the "critical dimension" explains why flat spacetime solutions are possible.^ Furthermore, the absence of potential energy in the "critical dimension" explains why flat spacetime solutions are possible.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ So, for a string in flat spacetime, c is the spacetime dimension.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ So one can construct a solution in which the four large dimensions stay approximately flat and the geometry of the Calabi-Yau manifold changes slowly from one Ricci flat metric to another.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

.This can be better understood by noting that a photon included in a consistent theory (technically, a particle carrying a force related to an unbroken gauge symmetry) must be massless.^ This can be better understood by noting that a photon included in a consistent theory (technically, a particle carrying a force related to an unbroken gauge symmetry) must be massless.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ Since it is via compactification, which yields local non-Abelian gauge symmetries, and other symmetry groups (to describe all the known particles and forces, plus some unknow ones), the mathematical treatment will be presented in the followings for a better understanding of the subject.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ The superstring theory is based on the introduction of a world sheet super-symmetry that relates the space-time coordinates X ( , ) to a fermionic partners ( , ), which are two-component world sheet spinors.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

.The mass of the photon which is predicted by string theory depends on the energy of the string mode which represents the photon.^ The mass of the photon which is predicted by string theory depends on the energy of the string mode which represents the photon.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ MDT predicts the equivalence of mass and energy.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ It is suggested that string theory has already been tested by the RHIC , which produced liquid quark-gluon plasma as predicted by the string theory.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

.This energy includes a contribution from the Casimir effect, namely from quantum fluctuations in the string.^ This energy includes a contribution from the Casimir effect, namely from quantum fluctuations in the string.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ Yet this prediction rests on two dubious assumptions: that ordinary physics may be applied to vacuum fluctuations at energy scales increasing exponentially without bound; and that quantum-gravitational effects may be neglected.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ Now, t’Hooft is a smart guy who has contributed to string theory, contributed massively to quantum field theory, and so forth.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.The size of this contribution depends on the number of dimensions since for a larger number of dimensions, there are more possible fluctuations in the string position.^ The size of this contribution depends on the number of dimensions since for a larger number of dimensions, there are more possible fluctuations in the string position.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ Is it possible to revise General Relativity in a way to describe the universe just as well as String Theory, but without all those extraneous spatial dimensions?
  • Evidence for String Theory!! - JREF Forum 28 January 2010 0:56 UTC forums.randi.org [Source type: FILTERED WITH BAYES]

^ Large Dimensions - Since the Planck length is the natural scale of strings, the most probable universe would be the one in which all of the dimensions are comparable to the Planck length.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

.Therefore, the photon in flat spacetime will be massless—and the theory consistent—only for a particular number of dimensions.^ This superstring is consistent in 10 spacetime dimensions.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ Therefore, the photon in flat spacetime will be massless?and the theory consistent?only for a particular number of dimensions.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ So, for a string in flat spacetime, c is the spacetime dimension.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

[13]
.When the calculation is done, the critical dimensionality is not four as one may expect (three axes of space and one of time).^ When the calculation is done, the critical dimensionality is not four as one may expect (three axes of space and one of time).
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ Events are therefore specified by four pieces of information: three in space and one in time.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ Space-Time Duality: Space-time duality would be more properly described as the duality between the three spatial and the fourth expanding dimension.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

.The subset of X is equal to the relation of photon fluxuations in a linear dimension.^ All points on that sphere will represent a single point in the fourth dimension, and the photon has an equal chance of being found at any point on the surface of the sphere.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

.Flat space string theories are 26-dimensional in the bosonic case, while superstring and M-theories turn out to involve 10 or 11 dimensions for flat solutions.^ In bosonic string theories, the 26 dimensions come from the Polyakov equation.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ In the heterotic string, the left mover is a bosonic string in 26 dimensions; while the right mover is a superstring in 10 dimensions: .
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ It is called the bosonic string theory .
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

.In bosonic string theories, the 26 dimensions come from the Polyakov equation.^ In bosonic string theories, the 26 dimensions come from the Polyakov equation.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ Now, one of the things that I think goes along with string theory, is talk about multiple dimensions .
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ Fraser: Isn't that one of the thoughts that (it goes back to string theory), that gravity is so weak because it is moving between multiple dimensions?
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

[14] .Starting from any dimension greater than four, it is necessary to consider how these are reduced to four dimensional spacetime.^ Starting from any dimension greater than four, it is necessary to consider how these are reduced to four dimensional space-time.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ Cosmological solutions exist in a wider variety of dimensionalities, and these different dimensions?more precisely different values of the "effective central charge," a count of degrees of freedom which reduces to dimensionality in weakly curved regimes?are related by dynamical transitions.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ Rather than imagine that the extra dimensions are very small, one can imagine that they are much larger and we live on a (3 + 1)-dimensional brane in this higher dimensional space.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

Compact dimensions

Two different ways have been proposed to resolve this apparent contradiction. .The first is to compactify the extra dimensions; i.e., the 6 or 7 extra dimensions are so small as to be undetectable by present day experiments.^ Rather than imagine that the extra dimensions are very small, one can imagine that they are much larger and we live on a (3 + 1)-dimensional brane in this higher dimensional space.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ Space-time is considered to be flat in our perception, Son said, and five of the extra dimensions are compacted into a small, finite sphere.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ The result is then generalized to compactify the extra 16 dimensions and finally to curl up six of the remaining ten dimensions.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

To retain a high degree of supersymmetry, these compactification spaces must be very special, as reflected in their holonomy. .A 6-dimensional manifold must have SU(3) structure, a particular case (torsionless) of this being SU(3) holonomy, making it a Calabi-Yau space, and a 7-dimensional manifold must have G2 structure, with G2 holonomy again being a specific, simple, case.^ Calabi-Yau portion of space.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ The problem with determining a correct Calabi-Yau space is related to the perturbative method used to perform the calculation.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ Once again, though, carrying through with such calculations requires that we know which Calabi-Yau space to take for the extra dimensions.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

.Such spaces have been studied in attempts to relate string theory to the 4-dimensional Standard Model, in part due to the computational simplicity afforded by the assumption of supersymmetry.^ No, it just means that it's a hypothesis, which is interesting in that it's consistent with the present Standard Model and ties up some loose ends theoretically, but still needs to be tested (in this regard, string theory is a misnomer).
  • Evidence for String Theory!! - JREF Forum 28 January 2010 0:56 UTC forums.randi.org [Source type: FILTERED WITH BAYES]

^ Although superstrings are formulated in a ten-dimensional space-time, in another sense a string field is also a theory about two-dimensional surfaces.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ In addition, the LHC (Large Hadron Collider, to be operational in April, 2008) will provide evidence or the lack of it for higher dimensions (in string theory ) and superpartners (in the theory of supersymmetry ).
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

.More recently, progress has been made constructing more realistic compactifications without the degree of symmetry of Calabi-Yau or G2 manifolds.^ Calabi-Yau Manifolds - As mentioned earlier there is a lot of difficulties to figure out the Calabi-Yau shape that agrees with the observed physical properties.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ However, considerable progress has been made recently for a class of states with large angular momentum on the S 5 or AdS 5 [ 31 , 32 ].
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ A realist would say that this progression is a more accurate approximation of truth.
  • Theory - Philosophy, Sociology & Psychology - Shroomery Message Board 28 January 2010 0:56 UTC www.shroomery.org [Source type: FILTERED WITH BAYES]

A standard analogy for this is to consider multidimensional space as a garden hose. .If the hose is viewed from a sufficient distance, it appears to have only one dimension, its length.^ Large Dimensions - Since the Planck length is the natural scale of strings, the most probable universe would be the one in which all of the dimensions are comparable to the Planck length.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ The fourth dimension is expanding relative to the three spatial dimensions in units of the Planck length, and thus distances smaller than the Planck length cannot be measured nor defined.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ The fourth dimension expands in units of the Planck length at the rate of c, so in a sense the fourth dimension is only ever Planck's length deep to all macroscopic objects.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

Indeed, think of a ball just small enough to enter the hose. .Throwing such a ball inside the hose, the ball would move more or less in one dimension; in any experiment we make by throwing such balls in the hose, the only important movement will be one-dimensional, that is, along the hose.^ One important consequence is that the fundamental higher dimensional Planck scale could be of the order of 1 TeV, and we might see quantum gravity or string theory effects at the Large Hadron Collider at CERN. This would be tremendously exciting, but it is important to remember that this is only one of many possible scenarios and it is not a unique prediction of string theory.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ Now, one of the things that I think goes along with string theory, is talk about multiple dimensions .
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ Rather than imagine that the extra dimensions are very small, one can imagine that they are much larger and we live on a (3 + 1)-dimensional brane in this higher dimensional space.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

However, as one approaches the hose, one discovers that it contains a second dimension, its circumference. .Thus, an ant crawling inside it would move in two dimensions (and a fly flying in it would move in three dimensions).^ Re: Moving Dimensions Theory's simplicity: The fourth dimension is expanding relative to the three spatial dimension: dx4/dt =ic .
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ Thus there exist neither philosophical nor physical barriers to the concept of moving dimensions, but for artificial ones within lazy minds.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ All particles will have a probability of being caught in the fourth expanding dimension in proportion to their energy, and thus there is a probability that the particles will move in a manner that approximates the expanding surfaces of the fourth dimension.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

.This "extra dimension" is only visible within a relatively close range to the hose, or if one "throws in" small enough objects.^ Thus there exist neither philosophical nor physical barriers to the concept of moving dimensions, but for artificial ones within lazy minds.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ Space-time is considered to be flat in our perception, Son said, and five of the extra dimensions are compacted into a small, finite sphere.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ But because time is a dimension, physicists were seduced into believing one could travel anywhere within it.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

.Similarly, the extra compact dimensions are only "visible" at extremely small distances, or by experimenting with particles with extremely small wavelengths (of the order of the compact dimension's radius), which in quantum mechanics means very high energies (see wave-particle duality).^ MDT predicts wave-particle duality.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ Quantum mechanics, relativity, and entropy--interference, wave- particle duality, quantized energy, time dialation, Lorentzian contractions, the equivalence of mass and energy, and times arrow all derive from the physical model moving dimensions theory presents.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ Quantum Mechanics treats the fourth dimension as a dynamical element.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

Brane-world scenario

Another possibility is that we are "stuck" in a 3+1 dimensional (i.e. three spatial dimensions plus the time dimension) subspace of the full universe. If such sub-spacetimes are exceptional sets within a larger-dimensional one, there typically exist properly localized matter and Yang-Mills gauge fields[15]. .These "exceptional sets" are ubiquitous in Calabi-Yau n-folds and may be described as subspaces without local deformations, akin to a crease in a sheet of paper or a crack in a crystal, the neighborhood of which is markedly different from the exceptional subspace itself.^ There are a few entries in the Calabi-Yau catalog that are closely akin to the particles of the standard model.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ Since the Calabi-Yau shape can be deformed in many ways (see Figure 07), there are literally an infinite variety of them.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

.However, until the work of Randall and Sundrum[16], it was not known that gravity too can be properly localized to a sub-spacetime; their proof that it can made such cosmological scenarios realistic.^ Then we’ve got this other proposal, loop quantum gravity, which has had fewer successes, but which does attempt such a local description at the Planck scale.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ He stressed that his opposition was not to the idea of describing spacetime in terms of local interactions of qubits, but rather to the specific technical program of loop quantum gravity, and to the exaggerated claims often made on that program’s behalf.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.In addition, spacetime may well be stratified, containing strata of various dimensions so that we may be inhabiting a 3+1 dimensional stratum; such geometries occur naturally Calabi-Yau compactifications[17].^ Once again, though, carrying through with such calculations requires that we know which Calabi-Yau space to take for the extra dimensions.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ Some may blame Josephson for what had not occurred, yet, this quest for understanding is quite strong as to how such processes work, not only, in a computer manufactured processes, but in a human capacity as well.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ The problem is that at present no one knows how to deduce from the equations of string which of the Calabi-Yau shapes constitutes the extra spatial dimensions.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

.Such sub-spacetimes are supposed to be D-branes, hence such models are known as a brane-world theories.^ Next one would like to count “physical states” of the theory, which induce a metric on spacetime such that that boundary has a certain surface area.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ Brane World - an introduction to the latest ideas from string theory Quarks & Strings - an introduction to the duality between quarks and string theory Understanding Nothing - the physics of the vacuum.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ So it is seen that Moving Dimensions Theory offers a simple model upon which all known phenomena of Relativity and Quantum Mechanics may rest.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

Effect of the hidden dimensions

.In either case, gravity acting in the hidden dimensions affects other non-gravitational forces such as electromagnetism.^ This lead to the equivalence of acceleration by an external force and the acceleration felt in the gravitational field, which lead to gravity being conceived as of the curvature of space-time.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ You can't expand around the point where gravity is the strongest force because a quantum theory of gravity in which gravity is stronger than other forces is inconsistent .
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ From the perspective of brane-bound particles, if it weren't for gravity or other bulk particles with which they might interact, the world might as well have only the dimensions of the branes.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

.In fact, Kaluza's early work demonstrated that general relativity in five dimensions actually predicts the existence of electromagnetism.^ MDT predicts entropy--the fundamental motion of the universe is the spherically-symmetric wavefront defiend by the fourth dimenion expanding relative to the three spatial dimensions--hence entropy.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ Another consequence of the fact that strings see the spacetime only through the sigma model is that spacetimes which are singular in general relativity can be completely nonsingular in string theory.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ I. Time as an Emergent Phenomenon Nowhere does Einstein?s relativity actually state that time is the fourth dimension, and MDT agrees that time is not the fourth dimension.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

.However, because of the nature of Calabi-Yau manifolds, no new forces appear from the small dimensions, but their shape has a profound effect on how the forces between the strings appear in our four-dimensional universe.^ Then finding a small number of Calabi-Yau shapes appear to be an extremely encouraging outcome.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ Once again, though, carrying through with such calculations requires that we know which Calabi-Yau space to take for the extra dimensions.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ Fraser: Isn't that one of the thoughts that (it goes back to string theory), that gravity is so weak because it is moving between multiple dimensions?
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

.In principle, therefore, it is possible to deduce the nature of those extra dimensions by requiring consistency with the standard model, but this is not yet a practical possibility.^ And it is testable in principle, not just in practice (yet).
  • Evidence for String Theory!! - JREF Forum 28 January 2010 0:56 UTC forums.randi.org [Source type: FILTERED WITH BAYES]

^ Once again, though, carrying through with such calculations requires that we know which Calabi-Yau space to take for the extra dimensions.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ Is it possible to revise General Relativity in a way to describe the universe just as well as String Theory, but without all those extraneous spatial dimensions?
  • Evidence for String Theory!! - JREF Forum 28 January 2010 0:56 UTC forums.randi.org [Source type: FILTERED WITH BAYES]

.It is also possible to extract information regarding the hidden dimensions by precision tests of gravity, but so far these have only put upper limitations on the size of such hidden dimensions.^ From the perspective of brane-bound particles, if it weren't for gravity or other bulk particles with which they might interact, the world might as well have only the dimensions of the branes.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ These lead to the suggestion that there is a weaker form of the holographic conjecture that applies only to the information measurable on the surface.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ So, I'll go out on a limb and say multiple dimensions is a ridiculous concept, but only because my limited knowledge is all I have to fall back on.
  • Evidence for String Theory!! - JREF Forum 28 January 2010 0:56 UTC forums.randi.org [Source type: FILTERED WITH BAYES]

D-branes

.Another key feature of string theory is the existence of D-branes.^ Although superstrings are formulated in a ten-dimensional space-time, in another sense a string field is also a theory about two-dimensional surfaces.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ Type I string theory contains D-branes with 1, 5, and 9 spatial dimensions.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ Scientists in 2006 offer another explanation for the paired images of CSL-1 via the reformulated theory of cosmic strings, which emerged from the cosmic inflation in a spaghetti-like tangle.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

.These are membranes of different dimensionality (anywhere from a zero dimensional membrane — which is in fact a point — and up, including 2-dimensional membranes, 3-dimensional volumes and so on).^ Thus, all the five string theories involve two-dimensional membranes, which become apparent in the strong coupling limit and show up in the 11th dimension.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ The name comes from membranes that are two-dimensional, but branes exist in any dimension: 0-branes are point particles, 1-branes are strings, etc.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ In terms of branes, what we usually call a membrane would be a two-brane, a string is called a one-brane and a point is called a zero-brane.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

D-branes are defined by the fact that worldsheet boundaries are attached to them. .Thus D-branes can emit and absorb closed strings; therefore they have mass (since they emit gravitons) and — in superstring theoriescharge as well (since they emit closed strings which are gauge bosons).^ It is called the bosonic string theory .
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ SO(32) Heterotic - This is a theory of closed string.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ Since the gauge bosons are also open strings, they would communicate a force that would act on the other brane-bound open strings with charge (at the endpoint).
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

.From the point of view of open strings, D-branes are objects to which the ends of open strings are attached.^ Since the gauge bosons are also open strings, they would communicate a force that would act on the other brane-bound open strings with charge (at the endpoint).
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ That's because the graviton is a closed string - a string with no ends would not be stuck to the brane at all.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ D-branes - A D-brane is a submanifold of space-time with the property that open strings can end or begin on it.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

.The open strings attached to a D-brane are said to "live" on it, and they give rise to gauge theories "living" on it (since one of the open string modes is a gauge boson such as the photon).^ It is called the bosonic string theory .
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ Since the gauge bosons are also open strings, they would communicate a force that would act on the other brane-bound open strings with charge (at the endpoint).
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ Now, one of the things that I think goes along with string theory, is talk about multiple dimensions .
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

.In the case of one D-brane there will be one type of a gauge boson and we will have an Abelian gauge theory (with the gauge boson being the photon).^ One of the important tasks is to rewrite string theory so that it is free from any particular choice of gauge or frame of reference.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ Just as in gauge field theory or general relativity, there are fewer independent dynamical degrees of freedom than appear explicitly in the action.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ There might or might not be a singularity behind the event horizon — one can ask the question in either case.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.If there are multiple parallel D-branes there will be multiple types of gauge bosons, giving rise to a non-Abelian gauge theory.^ Just as in gauge field theory or general relativity, there are fewer independent dynamical degrees of freedom than appear explicitly in the action.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ There are some theories that are attempting to find ways to make predictions based on multiple dimensions existing.
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ You can either look at it as perhaps there are multiple parallel universes.
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

.D-branes are thus gravitational sources, on which a gauge theory "lives". This gauge theory is coupled to gravity (which is said to exist in the bulk), so that normally each of these two different viewpoints is incomplete.^ The two theories are mathematically different and cannot be applied simultaneously.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ In any other case, including black hole horizons, the boundary metric still fluctuates and the boundary theory itself ought to be gravitational (if this notion even makes sense) and thus equally mysterious as the bulk theory.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ It would act as gravitational lens to produce two identical images of a light source from behind.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

Gauge-gravity duality

.Gauge-gravity duality is a conjectured duality between a quantum theory of gravity in certain cases and gauge theory in a lower number of dimensions.^ I won’t feel like I have any handle on this quantum-gravity business until I understand why the 2+1-dimensional case is so different from the case of 3+1 and higher dimensions.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ The extra 16 left mover dimensions provide the gauge group for the resulting 10-dimensional theory.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ String theory is a promising approach to a consistent quantum theory of gravity.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

.This means that each predicted phenomenon and quantity in one theory has an analogue in the other theory, with a "dictionary" translating from one theory to the other.^ Do Blackholes Radiate The prediction that black holes radiate due to quantum effects is often considered one of the most secure in quantum field theory in curved space-time.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ But it is like any other theory , it is the predictions that it makes which will decide it's usefullness.
  • Evidence for String Theory!! - JREF Forum 28 January 2010 0:56 UTC forums.randi.org [Source type: FILTERED WITH BAYES]

Description of the duality

.In certain cases the gauge theory on the D-branes is decoupled from the gravity living in the bulk; thus open strings attached to the D-branes are not interacting with closed strings.^ Gauge invariance can be added into the theory by attaching charges at the end of open strings (the charges are distributed on closed strings).
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ SO(32) Heterotic - This is a theory of closed string.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ One of the important tasks is to rewrite string theory so that it is free from any particular choice of gauge or frame of reference.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

Such a situation is termed a decoupling limit.
In those cases, the D-branes have two independent alternative descriptions. .As discussed above, from the point of view of closed strings, the D-branes are gravitational sources, and thus we have a gravitational theory on spacetime with some background fields.^ SO(32) Heterotic - This is a theory of closed string.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ In our view, the connection between quantum system engineering and string theory conceptually resembles the connection between Green functions and field theory (see, e.g.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ The former is a likely consequence of string theory — maybe even confirmed for some kinds of black holes, although I am not sure — while the latter always seemed inelegant to me.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.From the point of view of open strings, the physics of the D-branes is described by the appropriate gauge theory.^ There are open strings on the brane whose low-energy modes are described by a U ( N ) gauge theory.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ If the gauge theory is on S 3 × R with the radius of the three-sphere also given by , then the global time translation in the bulk agrees with time translation in the field theory and hence the energies of states in the field theory and string theory should agree.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ In our view, the connection between quantum system engineering and string theory conceptually resembles the connection between Green functions and field theory (see, e.g.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

Therefore in such cases it is often conjectured that the gravitational theory on spacetime with the appropriate background fields is dual (i.e. physically equivalent) to the gauge theory on the boundary of this spacetime (since the subspace filled by the D-branes is the boundary of this spacetime). .So far, this duality has not been proven in any cases, so there is also disagreement among string theorists regarding how strong the duality applies to various models.^ There isn't much; string theorists are the first to admit that.
  • Evidence for String Theory!! - JREF Forum 28 January 2010 0:56 UTC forums.randi.org [Source type: FILTERED WITH BAYES]

^ And there's plenty of string theorists beavering away trying to come up with other ways to test string theory, so it's certainly recognized as a priority in that community.
  • Evidence for String Theory!! - JREF Forum 28 January 2010 0:56 UTC forums.randi.org [Source type: FILTERED WITH BAYES]

^ This would presumably be the case in something like string theory, or in a model like the one you developed with Sundance and Fotini where matter content is derived from spin networks.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

Examples and intuition

.The most well-known example and the first one to be studied is the duality between Type IIB supergravity on AdS5 	imes S5 (a product space of a five-dimensional Anti de Sitter space and a five-sphere) on one hand, and N = 4 supersymmetric Yang-Mills theory on the four-dimensional boundary of the Anti de Sitter space (either a flat four-dimensional spacetime R3,1 or a three-sphere with time S3 	imes R).^ Events are therefore specified by four pieces of information: three in space and one in time.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ When the calculation is done, the critical dimensionality is not four as one may expect (three axes of space and one of time).
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ In this version of the theory, it is noted that solutions to the equation RAB = 0 with RAB the five-dimensional Ricci curvature, may be re-expressed so that in four dimensions, these solutions satisfy Einstein's equations Gμν = 8πTμν with the precise form of the Tμν following from the Ricci-flat condition on the five-dimensional space.

[18] .This is known as the AdS/CFT correspondence, a name often used for Gauge / gravity duality in general.^ Berenstein et al [ 31 ] showed what this Penrose limit corresponds to the dual gauge theory.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ In this way, one can extend the AdS/CFT correspondence to strings in a plane wave background.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ However, the AdS/CFT correspondence provides a natural solution.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

.This duality can be thought of as follows: suppose there is a spacetime with a gravitational source, for example an extremal black hole.^ Second, if the event horizon is not that of a black hole, there doesn’t have to be a singularity behind it.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ If it is then it means that the information must leak out after the black hole evaporates to the point that there is no longer an apparent horizon.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ Suppose that, as there is increasing theoretical evidence for from calculations, the spacelike singularity of the black hole is eliminated.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

[19] When particles are far away from this source, they are described by closed strings (i.e. a gravitational theory, or usually supergravity). .As the particles approach the gravitational source, they can still be described by closed strings; alternatively, they can be described by objects similar to QCD strings,[20][21][22] which are made of gauge bosons (gluons) and other gauge theory degrees of freedom.^ SO(32) Heterotic - This is a theory of closed string.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ The degree of freedom X is independent of each others.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ The left mover is described by the bosonic degrees of freedom in Eqs.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

[23] .So if one is able (in a decoupling limit) to describe the gravitational system as two separate regions — one (the bulk) far away from the source, and the other close to the source — then the latter region can also be described by a gauge theory on D-branes.^ There are also closed strings away from the brane.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ For the others, the ratio between the diâmetros diminishes for less of the one than two, then the ratio also enters the removal beats for less of the one than two.
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ Berenstein et al [ 31 ] showed what this Penrose limit corresponds to the dual gauge theory.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

.This latter region (close to the source) is termed the near-horizon limit, since usually there is an event horizon around (or at) the gravitational source.^ There might or might not be a singularity behind the event horizon — one can ask the question in either case.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ Let me repeat a point that seems to have been glossed over in much of this discussion: Black holes are not the only source of event horizons and Hawking radiation!
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ There is so far no difficulty because one has a pure state overall with the state in the new region entangled with the state external to the horizon.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.In the gravitational theory, one of the directions in spacetime is the radial direction, going from the gravitational source and away (towards the bulk).^ In the simplest case of flat spacetime with one direction compactified on a circle, this shows that a circle of radius R is equivalent to one with radius s 2 / R .
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ Do Blackholes Radiate The prediction that black holes radiate due to quantum effects is often considered one of the most secure in quantum field theory in curved space-time.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ But it might be one way of testing one set of theories that points toward multiple dimensions.
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

.The gauge theory lives only on the D-brane itself, so it does not include the radial direction: it lives in a spacetime with one less dimension compared to the gravitational theory (in fact, it lives on a spacetime identical to the boundary of the near-horizon gravitational theory).^ Now, one of the things that I think goes along with string theory, is talk about multiple dimensions .
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ Some boundary condtion is imposed on something that ensures that this boundary really does behave like a horizon.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ The extra 16 left mover dimensions provide the gauge group for the resulting 10-dimensional theory.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

Let us understand how the two theories are still equivalent:
.The physics of the near-horizon gravitational theory involves only on-shell states (as usual in string theory), while the field theory includes also off-shell correlation function.^ Although superstrings are formulated in a ten-dimensional space-time, in another sense a string field is also a theory about two-dimensional surfaces.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ Namely the only known good invariant at this time is say the SMatrix, or in other words physics at infinity (usually with nice asymptotic far fields).
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ Another consequence of the fact that strings see the spacetime only through the sigma model is that spacetimes which are singular in general relativity can be completely nonsingular in string theory.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

.The on-shell states in the near-horizon gravitational theory can be thought of as describing only particles arriving from the bulk to the near-horizon region and interacting there between themselves.^ Fraser: Isn't that one of the thoughts that (it goes back to string theory), that gravity is so weak because it is moving between multiple dimensions?
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ In any other case, including black hole horizons, the boundary metric still fluctuates and the boundary theory itself ought to be gravitational (if this notion even makes sense) and thus equally mysterious as the bulk theory.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ I have the feeling that non-renormalizability is not the only way to describe the diseases of string theory in dimensions other than 10 or 26.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.In the gauge theory these are "projected" onto the boundary, so that particles which arrive at the source from different directions will be seen in the gauge theory as (off-shell) quantum fluctuations far apart from each other, while particles arriving at the source from almost the same direction in space will be seen in the gauge theory as (off-shell) quantum fluctuations close to each other.^ In the Type IIA and IIB theory, these Weyl spinors have opposite and same chiralities respectively.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ In any other case, including black hole horizons, the boundary metric still fluctuates and the boundary theory itself ought to be gravitational (if this notion even makes sense) and thus equally mysterious as the bulk theory.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ One thus has the confusing situation that a two-dimensional CFT describes perturbative string excitations about this space, and a different two-dimensional CFT describes the entire theory.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

.Thus the angle between the arriving particles in the gravitational theory translates to the distance scale between quantum fluctuations in the gauge theory.^ In our view, the connection between quantum system engineering and string theory conceptually resembles the connection between Green functions and field theory (see, e.g.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ In any other case, including black hole horizons, the boundary metric still fluctuates and the boundary theory itself ought to be gravitational (if this notion even makes sense) and thus equally mysterious as the bulk theory.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ (I once spent a lot of time on them: On the nature of quantum fluctuations and their relation to gravitation and the principle of inertia} Classical and Quantum Gravity, 3 (1986) 347-359.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.The angle between arriving particles in the gravitational theory is related to the radial distance from the gravitational source at which the particles interact: the larger the angle, the closer the particles have to get to the source in order to interact with each other.^ But even in quantum field theory in non-linear coordinates, particle number is observer-dependent, because the coordinate change alters the dividing line between virtual and non-virtual particles.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ The coefficients are nothing other than the cosines of the angle between the original and new axes.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ From the perspective of brane-bound particles, if it weren't for gravity or other bulk particles with which they might interact, the world might as well have only the dimensions of the branes.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

.On the other hand, the scale of the distance between quantum fluctuations in a quantum field theory is related (inversely) to the energy scale in this theory.^ During the past 30 years, considerable progress has been made in giving a mathematically rigorous formulation of quantum field theory in curved spacetime.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ String theory allows one to relate the number of dimensions to scalar potential energy.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ In our view, the connection between quantum system engineering and string theory conceptually resembles the connection between Green functions and field theory (see, e.g.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

So small radius in the gravitational theory translates to low energy scale in the gauge theory (i.e. the IR regime of the field theory) while large radius in the gravitational theory translates to high energy scale in the gauge theory (i.e. the UV regime of the field theory).
A simple example to this principle is that if in the gravitational theory there is a setup in which the dilaton field (which determines the strength of the coupling) is decreasing with the radius, then its dual field theory will be asymptotically free, i.e. its coupling will grow weaker in high energies.

Contact with experiment

.This branch of string theory may lead to new insights on quantum chromodynamics, a gauge theory which is the fundamental theory of the strong nuclear force.^ String theory is a promising approach to a consistent quantum theory of gravity.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ However, Tutte’s rich and beautiful theory and methods are important in mathematics and quite fundamental in quantum gravity.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ If the gauge theory is on S 3 × R with the radius of the three-sphere also given by , then the global time translation in the bulk agrees with time translation in the field theory and hence the energies of states in the field theory and string theory should agree.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

.To this end, it is hoped that a gravitational theory dual to quantum chromodynamics will be found.^ If this hypothesis is true, then we have two separate worlds, the classical world of gravitation and the quantum world of atoms, described by separate theories.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ It is not yet clear how many quantum field theories have dual descriptions in terms of string theory.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ If so, will the dual description again be given in terms of a local quantum field theory?
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

[24]
.In fact, a vague contact with experiment has already been claimed to have been achieved,[6][7][8][9] though currently the alternative explanation for quark-gluon plasma behavior, Lattice QCD, is doing a much better job and has already made contact with experiments in various fields with good results,[25] though the computations are numerical rather than analytic.^ A quark-gluon plasma, in three spatial dimensions - behaves as if it has a viscosity near zero, the lowest yet measured."
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ This fact hints that conditions may be favorable for the production of a Quark-Gluon Plasma.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ Also, there are almost as many anti-protons as protons, which is another indication that conditions are favorable for the production of a Quark-Gluon Plasma.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

.Other possible experiments for string theory have been proposed.^ Thus string theory incorporates two major changes to the spacetime of general relativity that were proposed long before string theory became popular in the mid-1980s.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ There are other approaches to nonperturbative string theory such as string field theory.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ Is it possible to revise General Relativity in a way to describe the universe just as well as String Theory, but without all those extraneous spatial dimensions?
  • Evidence for String Theory!! - JREF Forum 28 January 2010 0:56 UTC forums.randi.org [Source type: FILTERED WITH BAYES]

.One is the discovery of large cosmic strings in space, formed when the high energies in the Big Bang "stretched" some strings to astronomical proportions.^ Considering the simple example of a bosonic string with one dimension (for both right and left movers) compactified on a circle, say X 25 in a form similar to Eq.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ In this form of calculation to meet the translation of the secondary one for the equatorial speed of the elementary school, it is Express that in agreement the diameter also diminishes the energy is lesser, decreases the maser.
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ Consequently, the high energy particle is detected indirectly, as cosmic ray primaries entering the Earth's atmosphere interact with atmospheric nuclei to produce large cascades of relativistic secondary particles known as extensive air showers.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

.Other possible avenues of experiment which could help provide evidence for string theory may take place at the newly built Large Hadron Collider.^ I'm looking for evidence for string theory.
  • Evidence for String Theory!! - JREF Forum 28 January 2010 0:56 UTC forums.randi.org [Source type: FILTERED WITH BAYES]

^ One important consequence is that the fundamental higher dimensional Planck scale could be of the order of 1 TeV, and we might see quantum gravity or string theory effects at the Large Hadron Collider at CERN. This would be tremendously exciting, but it is important to remember that this is only one of many possible scenarios and it is not a unique prediction of string theory.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ In addition, the LHC (Large Hadron Collider, to be operational in April, 2008) will provide evidence or the lack of it for higher dimensions (in string theory ) and superpartners (in the theory of supersymmetry ).
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

.One is the measurement of the strength of gravity on a microscopic scale, which could provide evidence for extra dimensions; if gravitons (which are closed strings) leak off the membrane, at small scales the force of gravity should be much greater than at large scales where the gravitons would have ample chance to leak away into the bulk.^ The tension of the string can be estimated from the strength of the force transmitted by the graviton.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ There are also closed strings away from the brane.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ Closed strings in lower dimensions can be viewed as compactifications of these membranes.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

.The discovery of supersymmetry could also be considered evidence since string theory was the first theory to require it, though other theories have managed to incorporate supersymmetry as well.^ I'm looking for evidence for string theory.
  • Evidence for String Theory!! - JREF Forum 28 January 2010 0:56 UTC forums.randi.org [Source type: FILTERED WITH BAYES]

^ The familiar extended dimensions, therefore, may very well also be in the shape of circles and hence subject to the R and 1/R physical identification of string theory.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ One of the new approaches to non-perturbative string theory involves M-theory and duality, which in fact force us to reconsider the central role played by strings in supersymmetry.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

.Also, the absence of supersymmetric particles at energies accessible to the LHC would not necessarily disprove string theory, since supersymmetry could exist but still be outside the accelerator's range.^ If anyone could manage to reconcile General Relativity and Quantum Mechanics, they would immediately win just about all of the major science awards that exist and be hailed as the greatest genius since Newton and Einstein.
  • Evidence for String Theory!! - JREF Forum 28 January 2010 0:56 UTC forums.randi.org [Source type: FILTERED WITH BAYES]

^ Since Type IIA string starts out with opposite chirality for the movers, now both movers would have the same chirality, i.e., it changes to a Type IIB string.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ Since the theory was supposed to account for, among other things, the quantized force of gravity, the strings could not be longer than the length scale where the granular structure of space-time becomes important, i.e., 10 -33 cm - the Planck length.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

Unsolved problems in physics
.Is there a string theory vacuum which exactly describes everything in our universe?^ It concerns string theory, the universe and God.
  • String Theory, the Universe and God. Bear with me. | SciGuy | Chron.com - Houston Chronicle 28 January 2010 0:56 UTC blogs.chron.com [Source type: Original source]

^ In our view, the connection between quantum system engineering and string theory conceptually resembles the connection between Green functions and field theory (see, e.g.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ I watched that two-part PBS series on string theory, and it was the consensus of physicists that there was no observable evidence at this time.
  • Evidence for String Theory!! - JREF Forum 28 January 2010 0:56 UTC forums.randi.org [Source type: FILTERED WITH BAYES]

Is it uniquely determined by low energy data?
Question mark2.svg

Problems and controversy

.Although string theory comes from physics, some say that string theory's current untestable status means that it should be classified as more of a mathematical framework for building models as opposed to a physical theory.^ However, that's not say that the theory is untestable.
  • Evidence for String Theory!! - JREF Forum 28 January 2010 0:56 UTC forums.randi.org [Source type: FILTERED WITH BAYES]

^ No, it just means that it's a hypothesis, which is interesting in that it's consistent with the present Standard Model and ties up some loose ends theoretically, but still needs to be tested (in this regard, string theory is a misnomer).
  • Evidence for String Theory!! - JREF Forum 28 January 2010 0:56 UTC forums.randi.org [Source type: FILTERED WITH BAYES]

^ There are a lot of different versions of string theory that all build off of one another in slightly different ways and come up with slightly different predictions and the things that they're predicting aren't unique to just string theory, there are other theories based on the more standard model of particle physics that make similar predictions.
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

[26] .Some go further, and say that string theory as a theory of everything is a failure.^ The former is a likely consequence of string theory — maybe even confirmed for some kinds of black holes, although I am not sure — while the latter always seemed inelegant to me.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ (Or I should say string theories, since as they say, there are five sensible ones, in addition to the problematic purely bosonic string theory.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ Nonetheless, as I understand it, t’Hooft has been saying that he would like humanity to replace not only string theory, but even quantum probability by something better.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

[27][28] This led to a public debate in 2007,[29][30] with one commentator expressing this opinion:
."For more than a generation, physicists have been chasing a will-o’-the-wisp called string theory.^ It is called the bosonic string theory .
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ Thus string theory incorporates two major changes to the spacetime of general relativity that were proposed long before string theory became popular in the mid-1980s.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ Another consequence of the fact that strings see the spacetime only through the sigma model is that spacetimes which are singular in general relativity can be completely nonsingular in string theory.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

The beginning of this chase marked the end of what had been three-quarters of a century of progress. .Dozens of string-theory conferences have been held, hundreds of new Ph.D.s have been minted, and thousands of papers have been written.^ One of the new approaches to non-perturbative string theory involves M-theory and duality, which in fact force us to reconsider the central role played by strings in supersymmetry.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ Someday, perhaps, a dramatic new experimental finding or theoretical breakthrough will change the situation vis-à-vis string theory and its competitors.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ These strings have a tension which defines a new fundamental length scale in the theory s .
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

.Yet, for all this activity, not a single new testable prediction has been made, not a single theoretical puzzle has been solved.^ Since then, new techniques were found to compute them directly and they all agree with the predictions of mirror symmetry [ 17 ].
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

.In fact, there is no theory so far—just a set of hunches and calculations suggesting that a theory might exist.^ There's just no evidence.
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ How would you justify Einstein working on relativity or past research in black holes if you dismiss them just because there was no evidence backing them.
  • Evidence for String Theory!! - JREF Forum 28 January 2010 0:56 UTC forums.randi.org [Source type: FILTERED WITH BAYES]

^ Just as in gauge field theory or general relativity, there are fewer independent dynamical degrees of freedom than appear explicitly in the action.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

.And, even if it does, this theory will come in such a bewildering number of versions that it will be of no practical use: a Theory of Nothing."^ But even in quantum field theory in non-linear coordinates, particle number is observer-dependent, because the coordinate change alters the dividing line between virtual and non-virtual particles.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ A large number of physicists think that string theory is not even testable enough to be considered "wrong".
  • String Theory, the Universe and God. Bear with me. | SciGuy | Chron.com - Houston Chronicle 28 January 2010 0:56 UTC blogs.chron.com [Source type: Original source]

^ It is not rigorously proven, but it’s understood fairly well at a “physics level of rigor.” Also, what does “If particle number is observer-dependent, then everything is” even mean ?
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

-- Jim Holt.[31]

Is string theory predictive?

.String theory as a theory of everything has been criticized as unscientific because it is so difficult to test by experiments.^ Fraser: Isn't that one of the thoughts that (it goes back to string theory), that gravity is so weak because it is moving between multiple dimensions?
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ I've contacted (because I went to them) the universities I was a student at, and looked at their physics books when I first heard of string theory.
  • Evidence for String Theory!! - JREF Forum 28 January 2010 0:56 UTC forums.randi.org [Source type: FILTERED WITH BAYES]

^ And there's plenty of string theorists beavering away trying to come up with other ways to test string theory, so it's certainly recognized as a priority in that community.
  • Evidence for String Theory!! - JREF Forum 28 January 2010 0:56 UTC forums.randi.org [Source type: FILTERED WITH BAYES]

The controversy concerns two properties:
  1. It is widely believed that any theory of quantum gravity would require extremely high energies to probe directly, higher by orders of magnitude than those that current experiments such as the Large Hadron Collider[32] can reach.
  2. String theory as it is currently understood has a huge number of equally possible solutions, called string vacua[33], and these vacua might be sufficiently diverse to explain almost any phenomena we might observe at lower energies.
.If these properties are true, string theory as a theory of everything would have little or no predictive power for low energy particle physics experiments.^ Particles & Strings - an overview of the frontier of particle physics and string theory.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ String Theory is a model for generating predictions about the way energy particles behave.
  • Evidence for String Theory!! - JREF Forum 28 January 2010 0:56 UTC forums.randi.org [Source type: FILTERED WITH BAYES]

^ No one yet knows what this matter is made of, but it is considered cold because its purported particles exist at low energies and they don't interact in ordinary matter in ways that yield light.
  • The Big Bang Theory - talk.origins | Google Groups 28 January 2010 0:56 UTC groups.google.com [Source type: FILTERED WITH BAYES]

[34][35] .Because the theory is so difficult to test, some theoretical physicists have asked if it can even be called a scientific theory.^ No, it just means that it's a hypothesis, which is interesting in that it's consistent with the present Standard Model and ties up some loose ends theoretically, but still needs to be tested (in this regard, string theory is a misnomer).
  • Evidence for String Theory!! - JREF Forum 28 January 2010 0:56 UTC forums.randi.org [Source type: FILTERED WITH BAYES]

^ The former is a likely consequence of string theory — maybe even confirmed for some kinds of black holes, although I am not sure — while the latter always seemed inelegant to me.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ But even in quantum field theory in non-linear coordinates, particle number is observer-dependent, because the coordinate change alters the dividing line between virtual and non-virtual particles.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.Notable critics include Peter Woit, Lee Smolin, Philip Warren Anderson,[36] Sheldon Glashow,[37] Lawrence Krauss[38], and Carlo Rovelli.^ Krauss and Susskind versus Horgan Peter Woit : I don’t see Horgan here criticizing the attempt to quantize gravity as “frivolous”.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ On the anti-string side, I read Peter Woit’s Not Even Wrong and Lee Smolin’s The Trouble With Physics .
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

[39]
.All string theory models are quantum mechanical, Lorentz invariant, unitary and contain Einstein's General Relativity as a low energy limit.^ This was the earliest indication that string theory incorporated general relativity.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ String Theory is a model for generating predictions about the way energy particles behave.
  • Evidence for String Theory!! - JREF Forum 28 January 2010 0:56 UTC forums.randi.org [Source type: FILTERED WITH BAYES]

^ If anyone could manage to reconcile General Relativity and Quantum Mechanics, they would immediately win just about all of the major science awards that exist and be hailed as the greatest genius since Newton and Einstein.
  • Evidence for String Theory!! - JREF Forum 28 January 2010 0:56 UTC forums.randi.org [Source type: FILTERED WITH BAYES]

[40] .Therefore to falsify string theory, it would suffice to falsify quantum mechanics, Lorentz invariance, or general relativity.^ This was the earliest indication that string theory incorporated general relativity.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ Thus string theory incorporates two major changes to the spacetime of general relativity that were proposed long before string theory became popular in the mid-1980s.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ The familiar extended dimensions, therefore, may very well also be in the shape of circles and hence subject to the R and 1/R physical identification of string theory.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

[41] .Hence string theory is falsifiable and meets the definition of scientific theory according to the Popperian criterion.^ In fact, since the gauge theory is defined nonperturbatively, one can view this as a nonperturbative and (mostly) background-independent definition of string theory.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ If the gauge theory is on S 3 × R with the radius of the three-sphere also given by , then the global time translation in the bulk agrees with time translation in the field theory and hence the energies of states in the field theory and string theory should agree.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ The familiar extended dimensions, therefore, may very well also be in the shape of circles and hence subject to the R and 1/R physical identification of string theory.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

.However to constitute a convincing potential verification of string theory, a prediction should be specific to it, not shared by any quantum field theory model or by General Relativity.^ Is it more important for a quantum gravity theory to connect to the Standard Model, or to build in background-independence from the outset?
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ Again, we’re talking about quantum gravity, so we presumably want our model to generate a simplicial representation of the causal structure of spacetime.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ This would presumably be the case in something like string theory, or in a model like the one you developed with Sundance and Fotini where matter content is derived from spin networks.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.One such unique prediction is string harmonics: at sufficiently high energies—probably near the quantum gravity scale—the string-like nature of particles would become obvious.^ Hence the quantum nature of all energy.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ Such a particle is necessary in quantum gravity, because energy is carried in discrete little packets called quanta, and a quantum of gravitational energy would behave like a particle.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ Nowhere does String Theory nor Loop Quantum Gravity resolve the paradox of Godel's Block Universe which troubled Einstein.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

.There should be heavier copies of all particles corresponding to higher vibrational states of the string.^ All particles will have a probability of being caught in the fourth expanding dimension in proportion to their energy, and thus there is a probability that the particles will move in a manner that approximates the expanding surfaces of the fourth dimension.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ (Or I should say string theories, since as they say, there are five sensible ones, in addition to the problematic purely bosonic string theory.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ It is estimated that the final burst should radiate a large number of particles in all directions with very high energies.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

But it is not clear how high these energies are. .In the most likely case, they would be 1015 times higher than those accessible in the newest particle accelerator, the LHC, making this prediction impossible to test with any particle accelerator in the foreseeable future.^ This would presumably be the case in something like string theory, or in a model like the one you developed with Sundance and Fotini where matter content is derived from spin networks.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ Rather than imagine that the extra dimensions are very small, one can imagine that they are much larger and we live on a (3 + 1)-dimensional brane in this higher dimensional space.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ I won’t feel like I have any handle on this quantum-gravity business until I understand why the 2+1-dimensional case is so different from the case of 3+1 and higher dimensions.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

Swampland

.In response to these concerns, Cumrun Vafa and others have challenged the idea that string theory is compatible with anything.^ It is true that string theory is, among other things, a cure for the non-renormalizability of gravity as a quantum field theory.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ I have the feeling that non-renormalizability is not the only way to describe the diseases of string theory in dimensions other than 10 or 26.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ When I reminded him that other people complain about exaggerated claims made on string theory’s behalf, he replied that the two cases were not even remotely comparable.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.They propose that most possible theories of low energy physics lie in the swampland.^ No matter what you call it, though, that substance and others similar to it could be the most-perfect fluids in existence because they have ultra-low viscosity, or resistance to flow, said Dam Thanh Son, an associate physics professor in the Institute for Nuclear Theory at the University of Washington.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ In quantum field theory, there is a standard procedure for integrating out high energy degrees of freedom and obtaining an effective theory at low energy.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ But whether an infinite universe is even possible is something we need a physical theory to tell us.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.The swampland is the collection of theories which could be true if gravity wasn't an issue, but which are not compatible with string theory.^ String theory is a promising approach to a consistent quantum theory of gravity.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ Fraser: Isn't that one of the thoughts that (it goes back to string theory), that gravity is so weak because it is moving between multiple dimensions?
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ It is true that string theory is, among other things, a cure for the non-renormalizability of gravity as a quantum field theory.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.An example of a theory in the swampland is quantum electrodynamics in the limit of very small electron charge.^ Given that causal structures of spacetimes are dynamically determined in the classical limit, I don’t see how one could ask for more in a quantum theory of gravity.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ Since this post about string theory, the message is that high-dimensional quantum gravity is a very different problem.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ Since quantum theory deals with the very small and general relativity with the very large, many physicists feel that, for all practical purposes, there is no need to attempt such an ultimate unification.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

.This limit is perfectly fine in quantum field theory — in fact, in this limit, the perturbation theory becomes better and better.^ Renormalizability plays a fundamental role in perturbative quantum field theory.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ We punch in the probability of this reference of quantum perception with cosmological data and if 13.7 billions years could be contained in the model, then what says the limit of this universe could not be contained in what this universe might have become?
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ In our view, the connection between quantum system engineering and string theory conceptually resembles the connection between Green functions and field theory (see, e.g.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.But in string theory, at the moment the charge of the lightest charged particle becomes less than the mass in natural units, the theory becomes inconsistent.^ We give a brief overview of the nature of spacetime emerging from string theory.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ I have the feeling that non-renormalizability is not the only way to describe the diseases of string theory in dimensions other than 10 or 26.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ You can't expand around the point where gravity is the strongest force because a quantum theory of gravity in which gravity is stronger than other forces is inconsistent .
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

.The reason is that two such charged massive particles will attract each other gravitationally more than they repel each other electrostatically, and could be used to form black holes.^ What could be more interesting than that?
  • String Theory, the Universe and God. Bear with me. | SciGuy | Chron.com - Houston Chronicle 28 January 2010 0:56 UTC blogs.chron.com [Source type: Original source]

^ We could cover the earth with rock dust and start to absorb carbon in a more natural fashion which, along with reducing emissions and using a combination of other initiatives, will have a better and faster response."

^ For the others, the ratio between the diâmetros diminishes for less of the one than two, then the ratio also enters the removal beats for less of the one than two.
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

.If there are no light charged particles, these black holes could not decay efficiently, barring improbable conspiracies or remnants.^ There is also a field theory interpretation of black hole quasinormal modes.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ If it is then it means that the information must leak out after the black hole evaporates to the point that there is no longer an apparent horizon.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ Suppose that, as there is increasing theoretical evidence for from calculations, the spacelike singularity of the black hole is eliminated.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.From the study of examples, and from the analysis of black-hole evaporation, it is now accepted that theories with a small charge quantum must come with light charged particles.^ This can be so even if the black hole evaporates in a finite amount of it.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ There is also a field theory interpretation of black hole quasinormal modes.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ If it is then it means that the information must leak out after the black hole evaporates to the point that there is no longer an apparent horizon.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.This is only true within string theory—there is no such restriction in quantum field theory.^ There are other approaches to nonperturbative string theory such as string field theory.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ There is also a field theory interpretation of black hole quasinormal modes.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ String theory is a promising approach to a consistent quantum theory of gravity.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

.This means that the discovery of a new gauge group with a small quantum of charge and only heavy charged particles would falsify string theory.^ One important consequence is that the fundamental higher dimensional Planck scale could be of the order of 1 TeV, and we might see quantum gravity or string theory effects at the Large Hadron Collider at CERN. This would be tremendously exciting, but it is important to remember that this is only one of many possible scenarios and it is not a unique prediction of string theory.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ The proposed "strings" are of an order of magnitude so much smaller than individual atoms or even subatomic particles that we'd need an entirely new toolset to do so.
  • Evidence for String Theory!! - JREF Forum 28 January 2010 0:56 UTC forums.randi.org [Source type: FILTERED WITH BAYES]

^ String theory is a promising approach to a consistent quantum theory of gravity.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

Since this argument is very general—relying only on black-hole evaporation and the holographic principle, it has been suggested that this prediction would be true of any consistent holographic theory of quantum gravity, although the phrase "consistent holographic theory of quantum gravity" might very well be synonymous with "string theory".
.It is notable that all the gross features of the Standard model can be embedded within String theory, so that the standard model is not in the swampland.^ No, it just means that it's a hypothesis, which is interesting in that it's consistent with the present Standard Model and ties up some loose ends theoretically, but still needs to be tested (in this regard, string theory is a misnomer).
  • Evidence for String Theory!! - JREF Forum 28 January 2010 0:56 UTC forums.randi.org [Source type: FILTERED WITH BAYES]

^ Another consequence of the fact that strings see the spacetime only through the sigma model is that spacetimes which are singular in general relativity can be completely nonsingular in string theory.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ In all the debates about string theory, he finally decided, From this day forward, my allegiances in the String Wars will be open for sale to t…… .
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.This includes features such as non-abelian gauge groups and chiral fermions which are hard to incorporate in non-string theories of quantum gravity.^ String theory is a promising approach to a consistent quantum theory of gravity.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ Thus string theory incorporates two major changes to the spacetime of general relativity that were proposed long before string theory became popular in the mid-1980s.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ However, Tutte’s rich and beautiful theory and methods are important in mathematics and quite fundamental in quantum gravity.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

[citation needed]

Background independence

.A separate and older criticism of string theory is that it is background-dependent — string theory describes perturbative expansions about fixed spacetime backgrounds.^ Spacetime in string theory .
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ But string theory is certainly not restricted to perturbing about flat spacetime.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ Thus string theory incorporates two major changes to the spacetime of general relativity that were proposed long before string theory became popular in the mid-1980s.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

.Although the theory has some background-independence — topology change is an established process in string theory, and the exchange of gravitons is equivalent to a change in the background — mathematical calculations in the theory rely on preselecting a background as a starting point.^ So let's start with string theory.
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ Thus string theory incorporates two major changes to the spacetime of general relativity that were proposed long before string theory became popular in the mid-1980s.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ So there are theories that work mathematically, but beyond things that they can predict that we'll find in the cosmic microwave background, these theories don't make testable predictions.
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

.This is because, like many quantum field theories, much of string theory is still only formulated perturbatively, as a divergent series of approximations.^ Renormalizability plays a fundamental role in perturbative quantum field theory.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ Many string theorists believe that string theory is the only possible renormalizable, perturbative theory of quantum gravity.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ One important consequence is that the fundamental higher dimensional Planck scale could be of the order of 1 TeV, and we might see quantum gravity or string theory effects at the Large Hadron Collider at CERN. This would be tremendously exciting, but it is important to remember that this is only one of many possible scenarios and it is not a unique prediction of string theory.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

.Although nonperturbative techniques have progressed considerably — including conjectured complete definitions in spacetimes satisfying certain asymptotics — a full non-perturbative definition of the theory is still lacking.^ Other CFTs with (typically) different spacetime dimensions are believed to provide a complete nonperturbative description of string theory with asymptotically AdS boundary conditions.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ We are thus led to the following general definition of perturbative string theory: perturbative string theory is equivalent to two-dimensional CFT with c = 26.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ String Theory and LQG lack definitive equations, whereas MDT presents a simple equation: It will be shown that relativity can be derived from this simple equation, as we return to Einstein?s original work.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

.Some see background independence as a fundamental requirement of a theory of quantum gravity, particularly since general relativity is already background independent.^ Thus string theory incorporates two major changes to the spacetime of general relativity that were proposed long before string theory became popular in the mid-1980s.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ One important consequence is that the fundamental higher dimensional Planck scale could be of the order of 1 TeV, and we might see quantum gravity or string theory effects at the Large Hadron Collider at CERN. This would be tremendously exciting, but it is important to remember that this is only one of many possible scenarios and it is not a unique prediction of string theory.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ String theory is a promising approach to a consistent quantum theory of gravity.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

.Some hope that M-theory, or a non-perturbative treatment of string theory (string field theory was thought to be non-perturbative in the 1980s) have a background-independent formulation.^ We have focused on the metric, but classical backgrounds for string theory can also include some matter fields.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ Thus string theory incorporates two major changes to the spacetime of general relativity that were proposed long before string theory became popular in the mid-1980s.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ Fraser: Isn't that one of the thoughts that (it goes back to string theory), that gravity is so weak because it is moving between multiple dimensions?
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

Supersymmetry breaking

.A central problem for applications is that the best understood backgrounds of string theory preserve much of the supersymmetry of the underlying theory, which results in time-invariant spacetimes: currently string theory cannot deal well with time-dependent, cosmological backgrounds.^ MDT: The Best-Tested Theory of All Time MDT is the best-tested theory of all time.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ Modern financial theory as applied ranks with string theory in physics as one of the greatest intellectual frauds of our time.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ This is where string theory gets itself into trouble: it's currently not testable.
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

However, several models have been proposed to explain supersymmetry breaking, most notably the KKLT model[33], which incorporates branes and fluxes to make a metastable compactification.
.The vacuum structure of the theory, called the string theory landscape, is not well understood.^ Instead, if you try to define string theory in the wrong dimension, the resulting disease is called “the conformal anomaly”.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ Brane World - an introduction to the latest ideas from string theory Quarks & Strings - an introduction to the duality between quarks and string theory Understanding Nothing - the physics of the vacuum.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ String theory leads to a stupendously large "landscape" of possibilities for the local laws of nature in a given pocket.
  • String Theory, the Universe and God. Bear with me. | SciGuy | Chron.com - Houston Chronicle 28 January 2010 0:56 UTC blogs.chron.com [Source type: Original source]

.String theory contains an infinite number of distinct meta-stable vacua, and perhaps 10500 of these or more correspond to a universe roughly similar to ours — with four dimensions, a high planck scale, gauge groups, and chiral fermions.^ It concerns string theory, the universe and God.
  • String Theory, the Universe and God. Bear with me. | SciGuy | Chron.com - Houston Chronicle 28 January 2010 0:56 UTC blogs.chron.com [Source type: Original source]

^ It is indeed interesting that M Theory and String Theory have 10 or 11 dimensions.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ Comments Erol Gokcedag Says: December 30th, 2007 at 2:17 am According to documentaries and articles I have read recently, the idea of an infinitely large universe is becoming more accepted by many scientists, and my own theories correspond with such an idea.
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

.Each of these corresponds to a different possible universe, with a different collection of particles and forces.^ Pamela: That's one possible way, or it could just be that the Universe was created so that gravity is a significantly weaker force.
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ Where with the uncertainty, every moment particles can do different things and then in one Universe the particle goes one way and then in an alternate reality the particle goes another way.
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ That's no different than saying Newton shouldn't have been "allowed" to consider the concept of universal forces or laws of motion.
  • String Theory, the Universe and God. Bear with me. | SciGuy | Chron.com - Houston Chronicle 28 January 2010 0:56 UTC blogs.chron.com [Source type: Original source]

[33] What principle, if any, can be used to select among these vacua is an open issue. .While there are no continuous parameters in the theory, there is a very large set of possible universes, which may be radically different from each other.^ Maybe there is no universe...
  • String Theory, the Universe and God. Bear with me. | SciGuy | Chron.com - Houston Chronicle 28 January 2010 0:56 UTC blogs.chron.com [Source type: Original source]

^ If the state is semiclassical there is a macroscopic notion of locality defined by the metric it is semiclassical to, but this may differ from microlocality in any of the basis states in the superposition that makes the semiclassical state.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ If we find microscopic black holes that may be proof that we live in a Universe with more than 5 dimensions, but no one's found a microscopic black hole yet.
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

.Some physicists believe this is a good thing, because it may allow a natural anthropic explanation of the observed values of physical constants, in particular the small value of the cosmological constant.^ But because time is a dimension, physicists were seduced into believing one could travel anywhere within it.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ I've seen some explanations that attempt to find reasons why the physical constant values might group into a much smaller range, thereby making the combinantion we see more likely.
  • String Theory, the Universe and God. Bear with me. | SciGuy | Chron.com - Houston Chronicle 28 January 2010 0:56 UTC blogs.chron.com [Source type: Original source]

^ You may argue the dark matter has not been directly observed, which is true, but many things that exist have never been directly observed.
  • The Big Bang Theory - talk.origins | Google Groups 28 January 2010 0:56 UTC groups.google.com [Source type: FILTERED WITH BAYES]

[42][43] .The argument is that most universes contain values for physical constants which do not lead to habitable universes (at least for humans), and so we happen to live in the most "friendly" universe.^ Whether or not the real universe in which we live is somehow five-dimensional is a topic that is debated and explored in several branches of physics, including astrophysics and particle physics.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ So many people throughout the ages can't accept the probability that humanity is simply another organism in the universe (one of many universes, most logically).
  • String Theory, the Universe and God. Bear with me. | SciGuy | Chron.com - Houston Chronicle 28 January 2010 0:56 UTC blogs.chron.com [Source type: Original source]

^ We live in a universe whose physical reality is that the fourth dimension is expanding relative to the three spatial dimensions.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

.This principle is already employed to explain the existence of life on earth as the result of a life-friendly orbit around the medium-sized sun among an infinite number of possible orbits (as well as a relatively stable location in the galaxy).^ Is it possible to revise General Relativity in a way to describe the universe just as well as String Theory, but without all those extraneous spatial dimensions?
  • Evidence for String Theory!! - JREF Forum 28 January 2010 0:56 UTC forums.randi.org [Source type: FILTERED WITH BAYES]

^ For that after the pass next to the sun the moon leaves with the closed orbit, that goes opening passing for the full one and in the declining room already if it finds well open, and enters open with 39,5 degrees of shift arc in longitude.
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ The size of this contribution depends on the number of dimensions since for a larger number of dimensions, there are more possible fluctuations in the string position.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

.However, the cosmological version of the anthropic principle remains highly controversial because it would be difficult if not impossible to Popper falsify; so many do not accept it as scientific.^ Critics say the anthropic principle is not science because it cannot be tested, or falsified.
  • String Theory, the Universe and God. Bear with me. | SciGuy | Chron.com - Houston Chronicle 28 January 2010 0:56 UTC blogs.chron.com [Source type: Original source]

^ Re: Critics say the anthropic principle is not science because it cannot be tested, or falsified.
  • String Theory, the Universe and God. Bear with me. | SciGuy | Chron.com - Houston Chronicle 28 January 2010 0:56 UTC blogs.chron.com [Source type: Original source]

^ Can one use the Anthropic Principle to make falsifiable predictions?
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

Other testability criteria

Many physicists strongly oppose the idea that string theory is not falsifiable, among them Sylvester James Gates: "So, the next time someone tells you that string theory is not testable, remind them of the AdS/CFT connection ..."[44] AdS/CFT relates string theory to gauge theory, and allows contact with low energy experiments in quantum chromodynamics. .This type of string theory, which only describes the strong interactions, is much less controversial today than string theories of everything (although two decades ago, it was the other way around).^ I have the feeling that non-renormalizability is not the only way to describe the diseases of string theory in dimensions other than 10 or 26.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ The proposed "strings" are of an order of magnitude so much smaller than individual atoms or even subatomic particles that we'd need an entirely new toolset to do so.
  • Evidence for String Theory!! - JREF Forum 28 January 2010 0:56 UTC forums.randi.org [Source type: FILTERED WITH BAYES]

^ For the others, the ratio between the diâmetros diminishes for less of the one than two, then the ratio also enters the removal beats for less of the one than two.
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

.In addition, Gates points out that the grand unification natural in string theories of everything requires that the coupling constants of the four forces meet at one point under renormalization group rescaling.^ Now, one of the things that I think goes along with string theory, is talk about multiple dimensions .
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ Fraser: Isn't that one of the thoughts that (it goes back to string theory), that gravity is so weak because it is moving between multiple dimensions?
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ Modern financial theory as applied ranks with string theory in physics as one of the greatest intellectual frauds of our time.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

.This is also a falsifiable statement, but it is not restricted to string theory, but is shared by grand unified theories.^ However, what really intrigues me is that the path string theory has led physicists down has led some of them to see the hand of a grand designer.
  • String Theory, the Universe and God. Bear with me. | SciGuy | Chron.com - Houston Chronicle 28 January 2010 0:56 UTC blogs.chron.com [Source type: Original source]

^ Pamela: String theory is a mathematical attempt to unify all the different forces.
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ I doubt many of us here can make any authoritative statement about the correctness of "String" or "M" theory.
  • Evidence for String Theory!! - JREF Forum 28 January 2010 0:56 UTC forums.randi.org [Source type: FILTERED WITH BAYES]

[45] .The LHC will be used both for testing AdS/CFT, and to check if the electroweakstrong unification does happen as predicted.^ But no inconsistency can arise from using both theories, because any differences between their predictions are physically undetectable.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

[46]

History

.Some of the structures reintroduced by string theory arose for the first time much earlier as part of the program of classical unification started by Albert Einstein.^ So let's start with string theory.
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ There isn't much; string theorists are the first to admit that.
  • Evidence for String Theory!! - JREF Forum 28 January 2010 0:56 UTC forums.randi.org [Source type: FILTERED WITH BAYES]

^ The former is a likely consequence of string theory — maybe even confirmed for some kinds of black holes, although I am not sure — while the latter always seemed inelegant to me.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.The first person to add a fifth dimension to general relativity was German mathematician Theodor Kaluza in 1919, who noted that gravity in five dimensions describes both gravity and electromagnetism in four.^ The theory was first published in 1921 and was discovered by the mathematician Theodor Kaluza who extended general relativity to a five-dimensional spacetime.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ It was discovered by the mathematician Theodor Kaluza that if general relativity is extended to a five-dimensional spacetime, the equations can be separated out into ordinary four-dimensional gravitation plus an extra set, which is equivalent to Maxwell's equations for the electromagnetic field, plus an extra scalar field known as the "dilaton".
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ So it is that quantum phenomena on the photonic level, as well as relativistic phenomena on the photonic level, are both accounted for with simple elegance via MDT: the fourth dimension is expanding relative to the three spatial dimensions.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

.In 1926, the Swedish physicist Oskar Klein gave a physical interpretation of the unobservable extra dimension--- it is wrapped into a small circle.^ MDT would underly all apsects of String Theory, and MDT does explain an interpretation of higher, numerous dimensions, if needed by Kaluza Klein et al.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ Oskar Klein proposed that the fourth spatial dimension is curled up with a very small radius, i.e.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ Space-time is considered to be flat in our perception, Son said, and five of the extra dimensions are compacted into a small, finite sphere.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

Einstein introduced a non-symmetric geometric tensor, while much later Brans and Dicke added a scalar component to gravity. .These ideas would be revived within string theory, where they are demanded by consistency conditions.^ So there are theories that work mathematically, but beyond things that they can predict that we'll find in the cosmic microwave background, these theories don't make testable predictions.
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ (Or I should say string theories, since as they say, there are five sensible ones, in addition to the problematic purely bosonic string theory.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ Nonetheless, as I understand it, t’Hooft has been saying that he would like humanity to replace not only string theory, but even quantum probability by something better.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.String theory was originally developed during the late 1960s and early 1970s as a never completely successful theory of hadrons, the subatomic particles like the proton and neutron which feel the strong interaction.^ With string theory you can throw in a bazillion different inputs and get an infinite number of outputs, it seems like.
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ The former is a likely consequence of string theory — maybe even confirmed for some kinds of black holes, although I am not sure — while the latter always seemed inelegant to me.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ Schramm’s SLE model, that was originated in the study of critical planar lattice models like loop-erased-random walks and percolation, is closely related also to conformal field theory which is quite prominent in string theory.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.In the 1960s, Geoffrey Chew and Steven Frautschi discovered that the mesons make families called Regge trajectories with masses related to spins in a way that was later understood by Yoichiro Nambu, Holger Bech Nielsen and Leonard Susskind to be the relationship expected from rotating strings.^ In later life he worked very hard to come up with ever more convoluted ways to make the Steady State theory explain the growing evidence.
  • The Big Bang Theory - talk.origins | Google Groups 28 January 2010 0:56 UTC groups.google.com [Source type: FILTERED WITH BAYES]

^ (I am borrowing heavily from noted string theorist Leonard Susskind ): .
  • String Theory, the Universe and God. Bear with me. | SciGuy | Chron.com - Houston Chronicle 28 January 2010 0:56 UTC blogs.chron.com [Source type: Original source]

.Chew advocated making a theory for the interactions of these trajectories which did not presume that they were composed of any fundamental particles, but would construct their interactions from self-consistency conditions on the S-matrix.^ This is a condition we would like to ask of a truly fundamental theory.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ Mark UK: "My points regarding Einstein and Newton is that they came up with a theory that explained their observations and that could be used to make predictions.
  • String Theory, the Universe and God. Bear with me. | SciGuy | Chron.com - Houston Chronicle 28 January 2010 0:56 UTC blogs.chron.com [Source type: Original source]

^ Thus there is a probability the particles will move about in random directions and undergo brownian motion, as they interact with other particles and energy.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

.The S-matrix approach was started by Werner Heisenberg in the 1940s as a way of constructing a theory which did not rely on the local notions of space and time, which Heisenberg believed break down at the nuclear scale.^ The theory therefore breaks down at all scales.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ Starting from any dimension greater than four, it is necessary to consider how these are reduced to four dimensional space-time.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ Do Blackholes Radiate The prediction that black holes radiate due to quantum effects is often considered one of the most secure in quantum field theory in curved space-time.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

.While the scale was off by many orders of magnitude, the approach he advocated was ideally suited for a theory of quantum gravity.^ Is it more important for a quantum gravity theory to connect to the Standard Model, or to build in background-independence from the outset?
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ Nowhere does String Theory nor Loop Quantum Gravity resolve the paradox of Godel's Block Universe which troubled Einstein.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ Given that causal structures of spacetimes are dynamically determined in the classical limit, I don’t see how one could ask for more in a quantum theory of gravity.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

Working with experimental data, R. Dolen, D. Horn and C. Schmid[47] developed some sum rules for hadron exchange. When a particle and antiparticle scatter, virtual particles can be exchanged in two qualitatively different ways. .In the s-channel, the two particles annihilate to make temporary intermediate states which fall apart into the final state particles.^ The LHC will have two such tubes placed side by side so that the same kind of particles - protons - can be accelerated in opposite directions and then smashed into each other.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ Two particles at a similar origin have a probability to move apart.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ Any two observers that drift apart (say they are parked in different galaxies) will see each other recede into each other’s backdrop event horizons.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

In the t-channel, the particles exchange intermediate states by emission and absorption. .In field theory, the two contributions add together, one giving a continuous background contribution, the other giving peaks at certain energies.^ Students forget that the use of (almost) every one of those fallacies emerges because of the great successes that the fallacy gives the reasoner in certain situations.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ Do Blackholes Radiate The prediction that black holes radiate due to quantum effects is often considered one of the most secure in quantum field theory in curved space-time.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ It is true that string theory is, among other things, a cure for the non-renormalizability of gravity as a quantum field theory.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.In the data, it was clear that the peaks were stealing from the background--- the authors interpreted this as saying that the t-channel contribution was dual to the s-channel one, meaning both described the whole amplitude and included the other.^ Or rather, when I say “the statement”, I am referring to one interpretation of Hawking radiation.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

The result was widely advertised by Murray Gell-Mann, leading Gabriele Veneziano to construct a scattering amplitude which had the property of Dolen-Horn-Schmid duality, later renamed world-sheet duality. .The amplitude needed poles where the particles appear, on straight line trajectories, and there is a special mathematical function whose poles are evenly spaced on half the real line--- the Gamma function--- which was widely used in Regge theory.^ Ramanujan Modular Forms Modular functions are used in the mathematical analysis of Riemann surfaces.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ So there are theories that work mathematically, but beyond things that they can predict that we'll find in the cosmic microwave background, these theories don't make testable predictions.
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ But even in quantum field theory in non-linear coordinates, particle number is observer-dependent, because the coordinate change alters the dividing line between virtual and non-virtual particles.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.By manipulating combinations of Gamma functions, Veneziano was able to find a consistent scattering amplitude with poles on straight lines, with mostly positive residues, which obeyed duality and had the appropriate Regge scaling at high energy.^ Gamma-Ray Bursts can be seen to high redshift, and this uniquely allows for tests as to whether the Dark Energy changes with time.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ (I.e., the theory posits that you integrate a constant function on its domain, which is the same as finding the volume of the domain.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ The result also highlights the Gamma-Ray Burst Hubble Diagram as a new front-line technique to measure Dark Energy and the high-redshift Universe.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

.The amplitude could fit near-beam scattering data as well as other Regge type fits, and had a suggestive integral representation which could be used for generalization.^ Ashoke Sen has suggested that more general theory could go by the name U-theory, which might stand for Ur, or Uber , or Ultimate, or Underlying, or perhaps Unified.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

Over the next years, hundreds of physicists worked to complete the bootstrap program for this model, with many surprises. .Veneziano himself discovered that for the scattering amplitude to describe the scattering of a particle which appears in the theory, an obvious self-consistency condition, the lightest particle must be a tachyon.^ Right now however the BB theory appears to describe what we see in our universe the best.
  • String Theory, the Universe and God. Bear with me. | SciGuy | Chron.com - Houston Chronicle 28 January 2010 0:56 UTC blogs.chron.com [Source type: Original source]

^ This can be better understood by noting that a photon included in a consistent theory (technically, a particle carrying a force related to an unbroken gauge symmetry) must be massless.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ Mark UK: "Right now however the BB theory appears to describe what we see in our universe the best."
  • String Theory, the Universe and God. Bear with me. | SciGuy | Chron.com - Houston Chronicle 28 January 2010 0:56 UTC blogs.chron.com [Source type: Original source]

Miguel Virasoro and Joel Shapiro found a different amplitude now understood to be that of closed strings, while Ziro Koba and Holger Nielsen generalized Veneziano's integral representation to multiparticle scattering. .Veneziano and Sergio Fubini introduced an operator formalism for computing the scattering amplitudes which was a forerunner of world-sheet conformal theory, while Virasoro understood how to remove the poles with wrong-sign residues using a constraint on the states.^ Instead, if you try to define string theory in the wrong dimension, the resulting disease is called “the conformal anomaly”.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ First, since the entanglement in Hawking radiation is hopelessly scrambled by the unitary operator of the black hole, it is hard to say how it has any computational value.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ What I understood is that when an observer A falls through the event horizon of an observer B, then reality is twinned, sort-of in the style of “many-worlds” theories.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

Claud Lovelace calculated a loop amplitude, and noted that there is an inconsistency unless the dimension of the theory is 26. Charles Thorn, Peter Goddard and Richard Brower went on to prove that there are no wrong-sign propagating states in dimensions less than or equal to 26.
.In 1969 Yoichiro Nambu, Holger Bech Nielsen and Leonard Susskind recognized that the theory could be given a description in space and time in terms of strings.^ Susskind agreed that such a convergence — between the “top-down” picture of string theory, which grew out of conventional high-energy physics, and a “bottom-up” picture in terms of qubits at the Planck scale — was possible or even likely.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ Fraser: But isn't that a sign of all of the different thinkings going into string theory – isn't that a sign of its health, of the possibilities that could exist there?
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ Given that causal structures of spacetimes are dynamically determined in the classical limit, I don’t see how one could ask for more in a quantum theory of gravity.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

The scattering amplitudes were derived systematically from the action principle by Peter Goddard, Jeffrey Goldstone, Claudio Rebbi and Charles Thorn, giving a space-time picture to the vertex operators introduced by Veneziano and Fubini and a geometrical interpretation to the Virasoro conditions.
In 1970, Pierre Ramond added fermions to the model, which led him to formulate a two-dimensional supersymmetry to cancel the wrong-sign states. John Schwarz and André Neveu added another sector to the fermi theory a short time later. .In the fermion theories, the critical dimension was 10. Stanley Mandelstam formulated a world sheet conformal theory for both the bose and fermi case, giving a two-dimensional field theoretic path-integral to generate the operator formalism.^ I won’t feel like I have any handle on this quantum-gravity business until I understand why the 2+1-dimensional case is so different from the case of 3+1 and higher dimensions.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ Schramm’s SLE model, that was originated in the study of critical planar lattice models like loop-erased-random walks and percolation, is closely related also to conformal field theory which is quite prominent in string theory.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ I have the feeling that non-renormalizability is not the only way to describe the diseases of string theory in dimensions other than 10 or 26.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.Michio Kaku and Keiji Kikkawa gave a different formulation of the bosonic string, as a string field theory, with infinitely many particle types and with fields taking values not on points, but on loops and curves.^ With string theory you can throw in a bazillion different inputs and get an infinite number of outputs, it seems like.
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ In our view, the connection between quantum system engineering and string theory conceptually resembles the connection between Green functions and field theory (see, e.g.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ In bosonic string theories, the 26 dimensions come from the Polyakov equation.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

.In 1974, Tamiaki Yoneya discovered that all the known string theories included a massless spin-two particle which obeyed the correct Ward identities to be a graviton.^ In all the debates about string theory, he finally decided, From this day forward, my allegiances in the String Wars will be open for sale to t…… .
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ When I reminded him that other people complain about exaggerated claims made on string theory’s behalf, he replied that the two cases were not even remotely comparable.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ Thus MDT underlies all string theories.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

.John Schwarz and Joel Scherk came to the same conclusion and made the bold leap to suggest that string theory was a theory of gravity, not a theory of hadrons.^ Fraser: Isn't that one of the thoughts that (it goes back to string theory), that gravity is so weak because it is moving between multiple dimensions?
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ So let me put this question to the experts: does either string theory or LQG suggest what the connection should be between entropy and the non-expansion of light rays?
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ It is true that string theory is, among other things, a cure for the non-renormalizability of gravity as a quantum field theory.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.They reintroduced Kaluza–Klein theory as a way of making sense of the extra dimensions.^ This is the only way that I can make sense of these stories.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ So there are theories that work mathematically, but beyond things that they can predict that we'll find in the cosmic microwave background, these theories don't make testable predictions.
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ At RHIC we don't make a "real" black hole, in the sense envisioned by Einstein's General Theory of Relativity.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

.At the same time, quantum chromodynamics was recognized as the correct theory of hadrons, shifting the attention of physicists and apparently leaving the bootstrap program in the dustbin of history.^ The point being, we’re all climbing the same mountain: mathematicians, physicists, and yes, quantum chemists and quantum system engineers too.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ Do Blackholes Radiate The prediction that black holes radiate due to quantum effects is often considered one of the most secure in quantum field theory in curved space-time.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ Einstein recognized Godel's paper as "an important contribution to the general theory of relativity," and since then physicists have not been able to find any logical shortcomings in Godel's work, and nobody has been able to account for the existence of time.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

.String theory eventually made it out of the dustbin, but for the following decade all work on the theory was completely ignored.^ In all the debates about string theory, he finally decided, From this day forward, my allegiances in the String Wars will be open for sale to t…… .
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ When I reminded him that other people complain about exaggerated claims made on string theory’s behalf, he replied that the two cases were not even remotely comparable.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ Thus MDT underlies all string theories.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

.Still, the theory continued to develop at a steady pace thanks the work of a handful of devotees.^ In later life he worked very hard to come up with ever more convoluted ways to make the Steady State theory explain the growing evidence.
  • The Big Bang Theory - talk.origins | Google Groups 28 January 2010 0:56 UTC groups.google.com [Source type: FILTERED WITH BAYES]

Ferdinando Gliozzi, Joel Scherk, and David Olive realized in 1976 that the original Ramond and Neveu Schwarz-strings were separately inconsistent and needed to be combined. .The resulting theory did not have a tachyon, and was proven to have space-time supersymmetry by John Schwarz and Michael Green in 1981. The same year, Alexander Polyakov gave the theory a modern path integral formulation, and went on to develop conformal field theory extensively.^ In our view, the connection between quantum system engineering and string theory conceptually resembles the connection between Green functions and field theory (see, e.g.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ This lead to the equivalence of acceleration by an external force and the acceleration felt in the gravitational field, which lead to gravity being conceived as of the curvature of space-time.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ Do Blackholes Radiate The prediction that black holes radiate due to quantum effects is often considered one of the most secure in quantum field theory in curved space-time.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

.In 1979, Daniel Friedan showed that the equations of motions of string theory, which are generalizations of the Einstein equations of General Relativity, emerge from the Renormalization group equations for the two-dimensional field theory.^ It is how Einstein discovered his field equations.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ In our view, the connection between quantum system engineering and string theory conceptually resembles the connection between Green functions and field theory (see, e.g.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ In bosonic string theories, the 26 dimensions come from the Polyakov equation.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

.Schwarz and Green discovered T-duality, and constructed two different superstring theories--- IIA and IIB related by T-duality, and type I theories with open strings.^ In our view, the connection between quantum system engineering and string theory conceptually resembles the connection between Green functions and field theory (see, e.g.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ The two theories are mathematically different and cannot be applied simultaneously.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ In all the debates about string theory, he finally decided, From this day forward, my allegiances in the String Wars will be open for sale to t…… .
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

The consistency conditions had been so strong, that the entire theory was nearly uniquely determined, with only a few discrete choices.
.In the early 1980s, Edward Witten discovered that most theories of quantum gravity could not accommodate chiral fermions like the neutrino.^ I won’t feel like I have any handle on this quantum-gravity business until I understand why the 2+1-dimensional case is so different from the case of 3+1 and higher dimensions.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ However, Tutte’s rich and beautiful theory and methods are important in mathematics and quite fundamental in quantum gravity.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ Do Blackholes Radiate The prediction that black holes radiate due to quantum effects is often considered one of the most secure in quantum field theory in curved space-time.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

.This led him, in collaboration with Luis Alvarez-Gaumé to study violations of the conservation laws in gravity theories with anomalies, concluding that type I string theories were inconsistent.^ It is true that string theory is, among other things, a cure for the non-renormalizability of gravity as a quantum field theory.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ However, what really intrigues me is that the path string theory has led physicists down has led some of them to see the hand of a grand designer.
  • String Theory, the Universe and God. Bear with me. | SciGuy | Chron.com - Houston Chronicle 28 January 2010 0:56 UTC blogs.chron.com [Source type: Original source]

^ When I reminded him that other people complain about exaggerated claims made on string theory’s behalf, he replied that the two cases were not even remotely comparable.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.Green and Schwarz discovered a contribution to the anomaly that Witten and Alvarez-Gaumé had missed, which restricted the gauge group of the type I string theory to be SO(32).^ In our view, the connection between quantum system engineering and string theory conceptually resembles the connection between Green functions and field theory (see, e.g.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ Instead, if you try to define string theory in the wrong dimension, the resulting disease is called “the conformal anomaly”.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ Now, t’Hooft is a smart guy who has contributed to string theory, contributed massively to quantum field theory, and so forth.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.In coming to understand this calculation, Edward Witten became convinced that string theory was truly a consistent theory of gravity, and he became a high-profile advocate.^ In bosonic string theories, the 26 dimensions come from the Polyakov equation.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ A direct response may just add fuel to controversies.’ - Dr Edward Witten, M-theory originator, Nature, Vol 444, 16 November 2006.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ It is true that string theory is, among other things, a cure for the non-renormalizability of gravity as a quantum field theory.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

Following Witten's lead, between 1984 and 1986, hundreds of physicists started to work in this field, and this is sometimes called the first superstring revolution.
During this period, David Gross, Jeffrey Harvey, Emil Martinec, and Ryan Rohm discovered heterotic strings. .The gauge group of these closed strings was two copies of E8, and either copy could easily and naturally include the standard model.^ That the connectiveness, would have ever acknowledged equative relations that these two photons under the squared earthbound views, would include all probabilites being still held to view.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ High Resolution 3D Hydrodynamic Simulations of Accretion Disks in Close Binaries Michael P. Owen Theoretical Astrophysics Group Department of Physics North Carolina State University So we look at the LHC model for comparison here in accretions disk energy formations, as we projectile these protons in either direction?
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ So how do you include such "weak field "manifestation in your global perspective(standard model).
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

.Philip Candelas, Gary Horowitz, Andrew Strominger and Edward Witten found that the Calabi-Yau manifolds are the compactifications which preserve a realistic amount of supersymmetry, while Lance Dixon and others worked out the physical properties of orbifolds, distinctive geometrical singularities allowed in string theory.^ String theory has the remarkable property of predicting gravity.’ - Dr Edward Witten, M-theory originator, Physics Today, April 1996.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ A direct response may just add fuel to controversies.’ - Dr Edward Witten, M-theory originator, Nature, Vol 444, 16 November 2006.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ Modern financial theory as applied ranks with string theory in physics as one of the greatest intellectual frauds of our time.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

Cumrun Vafa generalized T-duality from circles to arbitrary manifolds, creating the mathematical field of mirror symmetry. .David Gross and Vipul Periwal discovered that string perturbation theory was divergent in a way that suggested that new non-perturbative objects were missing.^ So let me put this question to the experts: does either string theory or LQG suggest what the connection should be between entropy and the non-expansion of light rays?
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ It is true that string theory is, among other things, a cure for the non-renormalizability of gravity as a quantum field theory.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ I have the feeling that non-renormalizability is not the only way to describe the diseases of string theory in dimensions other than 10 or 26.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.In the 1990s, Joseph Polchinski discovered that the theory requires higher-dimensional objects, called D-branes and identified these with the black-hole solutions of supergravity.^ In remarks to an American Physical Society newsletter, physicist Frank Wilczek of MIT called the black hole study a sound way to test an unattractive idea.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ The former is a likely consequence of string theory — maybe even confirmed for some kinds of black holes, although I am not sure — while the latter always seemed inelegant to me.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ Besides this, as far as I know, nobody has ever computed the Hawking radiation for a black hole with an infalling object.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.These were understood to be the new objects suggested by the perturbative divergences, and they opened up a new field with rich mathematical structure.^ Venn diagrams are used to represent classes of objects, and they can also assist us in reasoning about the relations between these classes.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ It was important to keep these two lines of investigation in perspective, as they diverged.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ Gamma ray bursts had to be used for the analysis - and they are sufficiently poorly understood - and independent experimental astrophysical sources at Harvard also recommend you to ignore the news.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

.It quickly became clear that D-branes and other p-branes, not just strings, formed the matter content of the string theories, and the physical interpretation of the strings and branes was revealed--- they are a type of black hole.^ But in the 10 dimensions of string theory, the fluid of a black hole isn't like other fluids.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ No matter what you call it, though, that substance and others similar to it could be the most-perfect fluids in existence because they have ultra-low viscosity, or resistance to flow, said Dam Thanh Son, an associate physics professor in the Institute for Nuclear Theory at the University of Washington.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ The former is a likely consequence of string theory — maybe even confirmed for some kinds of black holes, although I am not sure — while the latter always seemed inelegant to me.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.Leonard Susskind had incorporated the holographic principle of Gerardus 't Hooft into string theory, identifying the long highly-excited string states with ordinary thermal black hole states.^ The former is a likely consequence of string theory — maybe even confirmed for some kinds of black holes, although I am not sure — while the latter always seemed inelegant to me.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ Do Blackholes Radiate The prediction that black holes radiate due to quantum effects is often considered one of the most secure in quantum field theory in curved space-time.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ At RHIC we don't make a "real" black hole, in the sense envisioned by Einstein's General Theory of Relativity.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

.As suggested by 't Hooft, the fluctuations of the black hole horizon, the world-sheet or world-volume theory, describes not only the degrees of freedom of the black hole, but all nearby objects too.^ If it is then it means that the information must leak out after the black hole evaporates to the point that there is no longer an apparent horizon.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ The former is a likely consequence of string theory — maybe even confirmed for some kinds of black holes, although I am not sure — while the latter always seemed inelegant to me.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ Besides this, as far as I know, nobody has ever computed the Hawking radiation for a black hole with an infalling object.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.In 1995, at the annual conference of string theorists at the University of Southern California (USC), Edward Witten gave a speech on string theory that essentially united the five string theories that existed at the time, and giving birth to a new 11-dimensional theory called M-theory.^ It concerns string theory, the universe and God.
  • String Theory, the Universe and God. Bear with me. | SciGuy | Chron.com - Houston Chronicle 28 January 2010 0:56 UTC blogs.chron.com [Source type: Original source]

^ Nowhere does String Theory nor Loop Quantum Gravity resolve the paradox of Godel's Block Universe which troubled Einstein.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ Since this post about string theory, the message is that high-dimensional quantum gravity is a very different problem.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

M-theory was also foreshadowed in the work of Paul Townsend at approximately the same time. The flurry of activity which began at this time is sometimes called the second superstring revolution.
.During this period, Tom Banks, Willy Fischler Stephen Shenker and Leonard Susskind formulated a full holographic description of M-theory on IIA D0 branes[48], the first definition of string theory that was fully non-perturbative and a concrete mathematical realization of the holographic principle.^ DO realize the big bang has zip to do with string theory, right?
  • The Big Bang Theory - talk.origins | Google Groups 28 January 2010 0:56 UTC groups.google.com [Source type: FILTERED WITH BAYES]

^ However, what really intrigues me is that the path string theory has led physicists down has led some of them to see the hand of a grand designer.
  • String Theory, the Universe and God. Bear with me. | SciGuy | Chron.com - Houston Chronicle 28 January 2010 0:56 UTC blogs.chron.com [Source type: Original source]

^ First off, String theory is not the only or even leading theory attempting to explain the universe.
  • String Theory, the Universe and God. Bear with me. | SciGuy | Chron.com - Houston Chronicle 28 January 2010 0:56 UTC blogs.chron.com [Source type: Original source]

.Andrew Strominger and Cumrun Vafa calculated the entropy of certain configurations of D-branes and found agreement with the semi-classical answer for extreme charged black holes.^ Suppose that, as there is increasing theoretical evidence for from calculations, the spacelike singularity of the black hole is eliminated.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ If we find microscopic black holes that may be proof that we live in a Universe with more than 5 dimensions, but no one's found a microscopic black hole yet.
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ But if you don’t take semiclassical GR seriously, at least to the point of believing it gives a good approximation for large black holes and/or small Lambda, you shouldn’t believe in any of the calculations that lead to the conclusions that black holes and horizons have entropy and radiate.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.Petr Horava and Edward Witten found the eleven-dimensional formulation of the heterotic string theories, showing that orbifolds solve the chirality problem.^ A direct response may just add fuel to controversies.’ - Dr Edward Witten, M-theory originator, Nature, Vol 444, 16 November 2006.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ Fraser Cain: So here's the problem: we get questions sent in every week about the topics in the title of the show, especially string theory.
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ Since this post about string theory, the message is that high-dimensional quantum gravity is a very different problem.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.Witten noted that the effective description of the physics of D-branes at low energies is by a supersymmetric gauge theory, and found geometrical interpretations of mathematical structures in gauge theory that he and Nathan Seiberg had earlier discovered in terms of the location of the branes.^ Susskind agreed that such a convergence — between the “top-down” picture of string theory, which grew out of conventional high-energy physics, and a “bottom-up” picture in terms of qubits at the Planck scale — was possible or even likely.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ Therefore the energy is in agreement that astro acquired during the formation that the same will develop all its dynamics, orbit, phenomena and physical and chemical structure.
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ Brane World - an introduction to the latest ideas from string theory Quarks & Strings - an introduction to the duality between quarks and string theory Understanding Nothing - the physics of the vacuum.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

.In 1997 Juan Maldacena noted that the low energy excitations of a theory near a black hole consist of objects close to the horizon, which for extreme charged black holes looks like an anti de Sitter space.^ If it is then it means that the information must leak out after the black hole evaporates to the point that there is no longer an apparent horizon.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ Astrobiology Questions Show: Black black holes, Unbalancing the Earth, and Space Pollution Ep.
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ The former is a likely consequence of string theory — maybe even confirmed for some kinds of black holes, although I am not sure — while the latter always seemed inelegant to me.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.He noted that in this limit the gauge theory describes the string excitations near the branes.^ It can be used to refer to both the particular eleven-dimensional theory which Witten first proposed, or it can be used to refer to a kind of Uber theory which looks in various limits like the various string theories.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ Riemann surface theory is relevant to describing the behavior of strings as they move through space-time.
  • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

^ I have the feeling that non-renormalizability is not the only way to describe the diseases of string theory in dimensions other than 10 or 26.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.So he hypothesized that string theory on a near-horizon extreme-charged black-hole geometry, an anti-deSitter space times a sphere with flux, is equally well described by the low-energy limiting gauge theory, the N=4 supersymmetric Yang-Mills theory.^ If it is then it means that the information must leak out after the black hole evaporates to the point that there is no longer an apparent horizon.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ Astrobiology Questions Show: Black black holes, Unbalancing the Earth, and Space Pollution Ep.
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ MDT predicts the null vector for photons, as well as the - (minus) sign in the space-time metric.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

.This hypothesis, complemented by converging work due to Steven Gubser, Igor Klebanov and Alexander Polyakov, is called the AdS/CFT correspondence and it is now well-accepted.^ And that information comes out of a black hole is generally accepted to be quite well-established now.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.It is a concrete realization of the holographic principle, which has far-reaching implications for black holes, locality and information in physics, as well as the nature of the gravitational interaction.^ If individual gravitons cannot be observed in any conceivable experiment, then they have no physical reality and we might as well consider them sonexistent.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ If it is then it means that the information must leak out after the black hole evaporates to the point that there is no longer an apparent horizon.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ Besides this, as far as I know, nobody has ever computed the Hawking radiation for a black hole with an infalling object.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.Through this relationship, string theory has been shown to be related to gauge theories like quantum chromodynamics and this has led to more quantitative understanding of the behavior of hadrons, bringing string theory back to its roots.^ I won’t feel like I have any handle on this quantum-gravity business until I understand why the 2+1-dimensional case is so different from the case of 3+1 and higher dimensions.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ With string theory you can throw in a bazillion different inputs and get an infinite number of outputs, it seems like.
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

^ Fraser: Isn't that one of the thoughts that (it goes back to string theory), that gravity is so weak because it is moving between multiple dimensions?
  • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

See also

References

  1. ^ Sunil Mukhi(1999)"The Theory of Strings: A Detailed Introduction"
  2. ^ "NOVA - The elegant Universe"
  3. ^ Jim Holt, "Unstrung", The New Yorker, October 2, 2006
  4. ^ M. J. Duff, James T. Liu and R. Minasian Eleven Dimensional Origin of String/String Duality: A One Loop Test Center for Theoretical Physics, Department of Physics, Texas A&M University
  5. ^ Polchinski, Joseph (1998). String Theory, Cambridge University Press.
  6. ^ a b H. Nastase, The RHIC fireball as a dual black hole, BROWN-HET-1439, arXiv:hep-th/0501068, January 2005,
  7. ^ a b H. Nastase, More on the RHIC fireball and dual black holes, BROWN-HET-1466, arXiv:hep-th/0603176, March 2006,
  8. ^ a b H. Liu, K. Rajagopal, U. A. Wiedemann, An AdS/CFT Calculation of Screening in a Hot Wind, MIT-CTP-3757, arXiv:hep-ph/0607062 July 2006,
  9. ^ a b H. Liu, K. Rajagopal, U. A. Wiedemann, Calculating the Jet Quenching Parameter from AdS/CFT, Phys.Rev.Lett.97:182301,2006 arXiv:hep-ph/0605178
  10. ^ Burt A. Ovrut (2006). "A Heterotic Standard Model". Fortschritte der Physik 54-(2-3): 160–164. 
  11. ^ S. James Gates, Jr., Ph.D., Superstring Theory: The DNA of Reality "Lecture 23 - Can I Have that Extra Dimension in the Window?", 0:04:54, 0:21:00.
  12. ^ Simeon Hellerman and Ian Swanson(2006): "Dimension-changing exact solutions of string theory".; Ofer Aharony and Eva Silverstein(2006):"[Supercritical stability, transitions and (pseudo)tachyons http://arxiv.org/PS_cache/hep-th/pdf/0612/0612031v2.pdf]".
  13. ^ The calculation of the number of dimensions can be circumvented by adding a degree of freedom which compensates for the "missing" quantum fluctuations. However, this degree of freedom behaves similar to spacetime dimensions only in some aspects, and the produced theory is not Lorentz invariant, and has other characteristics which don't appear in nature. This is known as the linear dilaton or non-critical string.
  14. ^ "Quantum Geometry of Bosonic Strings – Revisited"
  15. ^ See, for example, T. Hübsch, "A Hitchhiker’s Guide to Superstring Jump Gates and Other Worlds", in Proc. SUSY 96 Conference, R. Mohapatra and A. Rasin (eds.), Nucl. Phys. (Proc. Supl.) 52A (1997) 347-351
  16. ^ L. Randall and R. Sundrum, "An Alternative to compactification" Phys. Rev. Lett. 83 (1999) 4690-4693
  17. ^ P. Aspinwall, D. Morrison and B. Greene, "Calabi-Yau moduli space, mirror manifolds and space-time topology change in string theory", Nucl. Phys. B416 (1994) 414-480
  18. ^ Aharony, O.; S.S. Gubser, J. Maldacena, H. Ooguri, Y. Oz (2000). "Large N Field Theories, String Theory and Gravity" (subscription required). Phys. Rept. 323: 183–386. doi:10.1016/S0370-1573(99)00083-6. http://arxiv.org/abs/hep-th/9905111. . For other examples see: arXiv:hep-th/9802042
  19. ^ Robbert Dijkgraaf,Erik Verlinde and Herman Verlinde(1997)"5D Black Holes and Matrix Strings"
  20. ^ Minoru Eto,Koji Hashimoto and Seiji Terashima(2007)"QCD String as Vortex String in Seiberg-Dual Theory"
  21. ^ Harvey B.Meyer(2005)"Vortices on the worldsheet of the QCD string"
  22. ^ Koji Hashimoto(2007)"Cosmic Strings, QCD Strings and D-branes"
  23. ^ Piljin Yi(2007)"Story of baryons in a gravity dual of QCD"
  24. ^ For example: T. Sakai and S. Sugimoto, Low energy hadron physics in holographic QCD, Prog.Theor.Phys.113:843-882,2005, arXiv:hep-th/0412141, December 2004
  25. ^ See for example Recent Results of the MILC research program, taken from the MILC Collaboration homepage
  26. ^ David Gross, Perspectives, String Theory: Achievements and Perspectives - A conference
  27. ^ Peter Woit's Not Even Wrong weblog
  28. ^ Lee Smolin's The Trouble With Physics webpage
  29. ^ e.g. John Baez and responses on the group weblog The n-Category Cafe
  30. ^ John Baez weblog
  31. ^ Unstrung: The New Yorker
  32. ^ Elias Kiritsis(2007)"String Theory in a Nutshell"
  33. ^ a b c S. Kachru, R. Kallosh, A. Linde and S. P. Trivedi, de Sitter Vacua in String Theory, Phys.Rev.D68:046005,2003, arXiv:hep-th/0301240
  34. ^ P. Woit (Columbia University), String theory: An Evaluation,February 2001, arXiv:physics/0102051
  35. ^ P. Woit, Is String Theory Testable? INFN Rome March 2007
  36. ^ "string theory is the first science in hundreds of years to be pursued in pre-Baconian fashion, without any adequate experimental guidance", New York Times, 4 January 2005
  37. ^ "there ain't no experiment that could be done nor is there any observation that could be made that would say, `You guys are wrong.' The theory is safe, permanently safe" NOVA interview)
  38. ^ "String theory [is] yet to have any real successes in explaining or predicting anything measurable" New York Times, 8 November 2005)
  39. ^ see his Dialog on Quantum Gravity, arXiv:hep-th/0310077)
  40. ^ J. Polchinski, String Theory, Cambridge University Press, Cambridge, UK (1998)
  41. ^ N. Comins, W. Kaufmann, Discovering the Universe: From the Stars to the Planets, W.H. Freeman & Co., p. 357 (2008)
  42. ^ N. Arkani-Hamed, S. Dimopoulos and S. Kachru, Predictive Landscapes and New Physics at a TeV, arXiv:hep-th/0501082, SLAC-PUB-10928, HUTP-05-A0001, SU-ITP-04-44, January 2005
  43. ^ L. Susskind The Anthropic Landscape of String Theory, arXiv:hep-th/0302219, February 2003
  44. ^ S. James Gates, Jr., Ph.D., Superstring Theory: The DNA of Reality "Lecture 21 - Can 4D Forces (without Gravity) Love Strings?", 0:26:06-0:26:21, cf. 0:24:05-0:26-24.
  45. ^ Idem, "Lecture 19 - Do-See-Do and Swing your Superpartner Part II" 0:16:05-0:24:29.
  46. ^ Idem, Lecture 21, 0:20:10-0:21:20.
  47. ^ Dolen, Horn, Schmid "Finite-Energy Sum Rules and Their Application to πN Charge Exchange" http://prola.aps.org/abstract/PR/v166/i5/p1768_1
  48. ^ Banks, Fischler, Shenker and Susskind "M Theory As A Matrix Model: A Conjecture" http://arxiv.org/abs/hep-th/9610043v3

Further reading

Popular books and articles

  • Davies, Paul; Julian R. Brown (Eds.) (July 31 1992). Superstrings: A Theory of Everything? (Reprint ed.). Cambridge: Cambridge University Press. pp. 244. ISBN 0-521-43775-X. 
  • Gefter, Amanda (December 2005). ."Is string theory in trouble?".^ Nowhere does String Theory nor Loop Quantum Gravity resolve the paradox of Godel's Block Universe which troubled Einstein.
    • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

    New Scientist. .http://www.newscientist.com/article/mg18825305.800-is-string-theory-in-trouble.html?full=true.^ Nowhere does String Theory nor Loop Quantum Gravity resolve the paradox of Godel's Block Universe which troubled Einstein.
    • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

    ^ It's entitled "The Universe on a String" and be found here: http://www.nytimes.com/2006/10/20/opinion/20greenehed.html?ex=1162008000&en=d9502612fdbdf34a&ei=5065&partner=MYWAY I've read a couple of Dr. Greens' books on string theory and have found it a very fascinating (if terribly complex) subject.
    • String Theory, the Universe and God. Bear with me. | SciGuy | Chron.com - Houston Chronicle 28 January 2010 0:56 UTC blogs.chron.com [Source type: Original source]

    ^ ECE Theory: http://www.aias.us and http://www.atomicprecision.com Prove Cartan Geometry wrong!
    • String Theory, the Universe and God. Bear with me. | SciGuy | Chron.com - Houston Chronicle 28 January 2010 0:56 UTC blogs.chron.com [Source type: Original source]

    .Retrieved December 19, 2005.
      – An interview with Leonard Susskind, the theoretical physicist who discovered that string theory is based on one-dimensional objects and now is promoting the idea of multiple universes.
  • Green, Michael (September 1986).^ It concerns string theory, the universe and God.
    • String Theory, the Universe and God. Bear with me. | SciGuy | Chron.com - Houston Chronicle 28 January 2010 0:56 UTC blogs.chron.com [Source type: Original source]

    ^ Now, one of the things that I think goes along with string theory, is talk about multiple dimensions .
    • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

    ^ Fraser: Isn't that one of the thoughts that (it goes back to string theory), that gravity is so weak because it is moving between multiple dimensions?
    • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

    "Superstrings". Scientific American. http://www.damtp.cam.ac.uk/user/mbg15/superstrings/superstrings.html. .Retrieved December 19, 2005. 
  • Greene, Brian (October 20 2003).^ Posted by: ttyler5 at October 20, 2006 01:19 AM .
    • String Theory, the Universe and God. Bear with me. | SciGuy | Chron.com - Houston Chronicle 28 January 2010 0:56 UTC blogs.chron.com [Source type: Original source]

    ^ Einstein Was Right (Again): ► 2005 (270) ► December (31) ► November (24) ► October (31) ► September (22) ► August (19) ► July (14) ► June (21) ► May (20) ► April (17) ► March (21) ► February (20) ► January (30) ► 2004 (84) ► December (30) ► November (54) .
    • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

    .The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory (Reissue ed.^ String theory and its 11 dimensions predict that something on the order of 10 (to the 500th power) "pocket universes" exist.
    • String Theory, the Universe and God. Bear with me. | SciGuy | Chron.com - Houston Chronicle 28 January 2010 0:56 UTC blogs.chron.com [Source type: Original source]

    ^ Flat space string theories are 26-dimensional in the bosonic case, while superstring and M-theories turn out to involve 10 or 11 dimensions for flat solutions.
    • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

    ^ MDT & Brian Greene?s Elegant Universe In An Elegant Universe, Brian Greene almost characterizes the reality of Moving Dimensions Theory, but falls just short.
    • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

    ). New York: W.W. Norton & Company. pp. 464. ISBN 0-393-05858-1. 
  • Greene, Brian (2004). .The Fabric of the Cosmos: Space, Time, and the Texture of Reality.^ This property gives rise to the concept of mass, as to exist in the spatial dimension curves the fabric of space-time about the existence.
    • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

    ^ Page 123 , The Fabric of the Cosmo , by Brian Greene Does gravity vary over time ?
    • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

    ^ Like it or not Stan, reality is just as relative as time, space and probably everything else.
    • String Theory, the Universe and God. Bear with me. | SciGuy | Chron.com - Houston Chronicle 28 January 2010 0:56 UTC blogs.chron.com [Source type: Original source]

    New York: Alfred A. Knopf. pp. 569. ISBN 0-375-41288-3.
     
  • Gribbin, John (1998). .The Search for Superstrings, Symmetry, and the Theory of Everything.^ The Search for the Theory of Everything Student Questions Show: Leelanau School Ep.
    • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

    London: Little Brown and Company. pp. 224. ISBN 0-316-32975-4.
     
  • Halpern, Paul (2004). .The Great Beyond: Higher Dimensions, Parallel Universes, and the Extraordinary Search for a Theory of Everything.^ But pursuers of this "theory of everything" have wandered into fantasy realms of higher dimensions with little or no empirical connection to our reality.
    • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

    ^ Multiple dimensions gets you into a slightly different picture though, where everything is chewing forward in the same universe.
    • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

    ^ MDT would underly all apsects of String Theory, and MDT does explain an interpretation of higher, numerous dimensions, if needed by Kaluza Klein et al.
    • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

    Hoboken, New Jersey: John Wiley & Sons, Inc.. pp. 326. ISBN 0-471-46595-X.
     
  • Hooper, Dan (2006). .Dark Cosmos: In Search of Our Universe's Missing Mass and Energy.^ While I had thought these relevant to Dark energy creation in our Cosmo, I did not point directly to the nature of these strangelets gathering at the center of our planet.
    • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

    ^ If held to current technologies and pre producable themes held in context of our cosmo, can we take such levels of dark energy production to be from the cause of strange quark productions?
    • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

    ^ This number tells you how quickly the dark energy density changes as the universe expands; if w=-1, the density is strictly constant, if w> -1, the density decreases, and if w <-1, the density actually increases with time.
    • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

    New York: HarperCollins. pp. 240. ISBN 978-0-06-113032-8.
     
  • Kaku, Michio (April 1994). .Hyperspace: A Scientific Odyssey Through Parallel Universes, Time Warps, and the Tenth Dimension.^ Transcript: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang .
    • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

    ^ It starts off with the premise that our Universe doesn't exist just in the three spatial dimensions we experience, and time, but rather it has other dimensions as well.
    • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

    ^ String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang .
    • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

    Oxford: Oxford University Press. pp. 384. ISBN 0-19-508514-0.
     
  • Klebanov, Igor and Maldacena, Juan (January 2009). .Solving Quantum Field Theories via Curved Spacetimes.^ In our view, the connection between quantum system engineering and string theory conceptually resembles the connection between Green functions and field theory (see, e.g.
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    ^ But even in quantum field theory in non-linear coordinates, particle number is observer-dependent, because the coordinate change alters the dividing line between virtual and non-virtual particles.
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    ^ Do Blackholes Radiate The prediction that black holes radiate due to quantum effects is often considered one of the most secure in quantum field theory in curved space-time.
    • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

    Physics Today.
  • Musser, George (2008). .The Complete Idiot's Guide to String Theory.^ The Complete Idiot's Guide to Christianity .
    • String Theory, the Universe and God. Bear with me. | SciGuy | Chron.com - Houston Chronicle 28 January 2010 0:56 UTC blogs.chron.com [Source type: Original source]

    Indianapolis: Alpha. pp. 368. ISBN 978-1-59-257702-6.
     
  • Randall, Lisa (September 1 2005). Warped Passages: Unraveling the Mysteries of the Universe's Hidden Dimensions. New York: Ecco Press. pp. 512. .ISBN 0-06-053108-8. 
  • Susskind, Leonard (December 2006).^ This entry was posted on Thursday, December 21st, 2006 at 8:06 am and is filed under Adventures in Meatspace , Complexity , Quantum .
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    ^ Lee Smolin Says: Comment #54 December 23rd, 2006 at 10:06 pm Dear Moshe, .
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    ^ John Preskill Says: Comment #4 December 21st, 2006 at 3:20 pm I know from experience that arguing with Lenny Susskind can be extraordinarily enlightening.
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    .The Cosmic Landscape: String Theory and the Illusion of Intelligent Design.^ Posted by Plato at Sunday, January 29, 2006 0 Dialogos of Eide Labels: Cosmic Strings , Gravity , Nothing , Particles , Quantum Gravity , Quarks , String Theory Links to this post .
    • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

    New York: Hachette Book Group/Back Bay Books. pp. 403. ISBN 0-316-01333-1. 
  • Taubes, Gary (November 1986). "Everything's Now Tied to Strings" Discover Magazine vol 7, #11. (Popular article, probably the first ever written, on the first superstring revolution.)
  • Vilenkin, Alex (2006). .Many Worlds in One: The Search for Other Universes.^ But like anything, there are so many maths in which to talk about the world in such an abstract way, one wonders if they are actually talking about reality?
    • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

    ^ One model leads to a finite universe, the other leads to an infinite universe.
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    New York: Hill and Wang. pp. 235. ISBN 0-8090-9523-8.
     
  • Witten, Edward (June 2002). "The Universe on a String" (PDF). Astronomy Magazine. http://www.sns.ias.edu/~witten/papers/string.pdf. Retrieved December 19, 2005.  – An easy nontechnical article on the very basics of the theory.
Two nontechnical books that are critical of string theory:
.
  • Smolin, Lee (2006).^ Lee Smolin Says: Comment #88 December 25th, 2006 at 5:39 am Dear William, .
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    ^ Lee Smolin Says: Comment #75 December 24th, 2006 at 7:00 pm Dear Greg, .
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    ^ Lee Smolin Says: Comment #93 December 25th, 2006 at 5:25 pm Aaron, .
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    .The Trouble with Physics: The Rise of String Theory, the Fall of a Science, and What Comes Next.^ In bosonic string theories, the 26 dimensions come from the Polyakov equation.
    • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

    ^ Modern financial theory as applied ranks with string theory in physics as one of the greatest intellectual frauds of our time.
    • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

    ^ This is where string theory gets itself into trouble: it's currently not testable.
    • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

    New York: Houghton Mifflin Co.. pp. 392. ISBN 0-618-55105-0. 
  • Woit, Peter (2006). .Not Even Wrong - The Failure of String Theory And the Search for Unity in Physical Law.^ The former is a likely consequence of string theory — maybe even confirmed for some kinds of black holes, although I am not sure — while the latter always seemed inelegant to me.
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    ^ Modern financial theory as applied ranks with string theory in physics as one of the greatest intellectual frauds of our time.
    • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

    ^ Susskind agreed that such a convergence — between the “top-down” picture of string theory, which grew out of conventional high-energy physics, and a “bottom-up” picture in terms of qubits at the Planck scale — was possible or even likely.
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    London: Jonathan Cape &: New York: Basic Books. pp. 290. ISBN 0-224-07605-1 & ISBN 978-0-465-09275-8.
     

Textbooks

.
  • Becker, Katrin, Becker, Melanie, and John H. Schwarz (2007) String Theory and M-Theory: A Modern Introduction .^ Modern financial theory as applied ranks with string theory in physics as one of the greatest intellectual frauds of our time.
    • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

    ^ Brane World - an introduction to the latest ideas from string theory Quarks & Strings - an introduction to the duality between quarks and string theory Understanding Nothing - the physics of the vacuum.
    • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

    ^ A less problematic approach to the unification of the forces is taken by modern string theory and M-theory.
    • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

    Cambridge University Press. ISBN 0-521-86069-5
  • Binétruy, Pierre (2007) Supersymmetry: Theory, Experiment, and Cosmology. Oxford University Press. .ISBN 978-0-19-850954-7.
  • Dine, Michael (2007) Supersymmetry and String Theory: Beyond the Standard Model.^ This would presumably be the case in something like string theory, or in a model like the one you developed with Sundance and Fotini where matter content is derived from spin networks.
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    ^ Is it more important for a quantum gravity theory to connect to the Standard Model, or to build in background-independence from the outset?
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    Cambridge University Press. ISBN 0-521-85841-0.
  • Paul H. Frampton (1974). Dual Resonance Models. Frontiers in Physics. ISBN 0-805-32581-6. 
  • Gasperini, Maurizio (2007) Elements of String Cosmology. Cambridge University Press. .ISBN 978-0-521-86875-4.
  • Michael Green, John H. Schwarz and Edward Witten (1987) Superstring theory.^ A direct response may just add fuel to controversies.’ - Dr Edward Witten, M-theory originator, Nature, Vol 444, 16 November 2006.
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    ^ String theory has the remarkable property of predicting gravity.’ - Dr Edward Witten, M-theory originator, Physics Today, April 1996.
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    Cambridge University Press. The original textbook.
    • Vol. 1: Introduction. ISBN 0-521-35752-7.
    • Vol. 2: Loop amplitudes, anomalies and phenomenology. ISBN 0-521-35753-5.
  • Kiritsis, Elias (2007) String Theory in a Nutshell. Princeton University Press. ISBN 978-0-691-12230-4.
  • Johnson, Clifford (2003). D-branes. Cambridge: Cambridge University Press. .ISBN 0-521-80912-6. 
  • Polchinski, Joseph (1998) String Theory.^ Update on cosmic strings Joseph Polchinski KITP, UCSB Joseph Polchinski, KITP, UCSB: Update on cosmic strings .
    • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

    Cambridge University Press.
    • Vol. 1: An introduction to the bosonic string. ISBN 0-521-63303-6.
    • Vol. 2: Superstring theory and beyond. .ISBN 0-521-63304-4.
  • Szabo, Richard J. (Reprinted 2007) An Introduction to String Theory and D-brane Dynamics.^ Brane World - an introduction to the latest ideas from string theory Quarks & Strings - an introduction to the duality between quarks and string theory Understanding Nothing - the physics of the vacuum.
    • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

    Imperial College Press. .ISBN 978-1-86094-427-7.
  • Zwiebach, Barton (2004) A First Course in String Theory.^ I, of course, always think in terms of the second concept, but I agree with you that a fundamental theory ought to connect somehow to the first one.
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    ^ It can be used to refer to both the particular eleven-dimensional theory which Witten first proposed, or it can be used to refer to a kind of Uber theory which looks in various limits like the various string theories.
    • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

    ^ I am of course thinking about free string theory in D dimensions, which can be regarded as QG in 2d coupled to D scalar fields.
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    Cambridge University Press. ISBN 0-521-83143-1. Contact author for errata.
Technical and critical:
  • Penrose, Roger (February 22 2005). .The Road to Reality: A Complete Guide to the Laws of the Universe.^ This imaginary, mathematical black hole that Horatiu compares to the RHIC fireball is completely different from a black hole in the real universe; in particular, it cannot grow by gobbling up matter.
    • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

    Knopf. pp. 1136. ISBN 0-679-45443-8.
     

Online material

  • Schwarz, John H. (2000). "Introduction to Superstring Theory". arXiv.org e-Print archive. .http://arxiv.org/abs/hep-ex/0008017.^ I’m aware of the species problem; in fact Ted Jacobson has a good paper on why it isn’t really a problem: http://arxiv.org/abs/gr-qc/9404039.
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    Retrieved December 22, 2005
    .
      – Four lectures, presented at the NATO Advanced Study Institute on Techniques and Concepts of High Energy Physics, St. Croix, Virgin Islands, in June 2000, and addressed to an audience of graduate students in experimental high energy physics, survey basic concepts in string theory.
  • Witten, Edward (1998). "Duality, Spacetime and Quantum Mechanics". Kavli Institute for Theoretical Physics. http://online.itp.ucsb.edu/online/plecture/witten/. .Retrieved December 16, 2005.  – Slides and audio from an Ed Witten lecture where he introduces string theory and discusses its challenges.
  • Kibble, Tom (2004).^ Aaron Bergman Says: Comment #113 December 31st, 2006 at 4:40 pm Renormalizable isn’t the word I would use for string theory.
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    ^ It can be used to refer to both the particular eleven-dimensional theory which Witten first proposed, or it can be used to refer to a kind of Uber theory which looks in various limits like the various string theories.
    • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

    ^ Greg Kuperberg Says: Comment #49 December 23rd, 2006 at 3:55 am Although string theory is mostly over my head, I have studied general relativity.
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    "Cosmic strings reborn?". arXiv.org e-Print archive. .http://arxiv.org/abs/astro-ph/0410073/.^ I’m aware of the species problem; in fact Ted Jacobson has a good paper on why it isn’t really a problem: http://arxiv.org/abs/gr-qc/9404039.
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    .Retrieved December 16, 2005.
      – Invited Lecture at COSLAB 2004, held at Ambleside, Cumbria, United Kingdom, from 10 to 17 September 2004.
  • Marolf, Don (2004).^ Einstein Was Right (Again): ► 2005 (270) ► December (31) ► November (24) ► October (31) ► September (22) ► August (19) ► July (14) ► June (21) ► May (20) ► April (17) ► March (21) ► February (20) ► January (30) ► 2004 (84) ► December (30) ► November (54) .
    • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

    "Resource Letter NSST-1: The Nature and Status of String Theory". arXiv.org e-Print archive. .http://arxiv.org/abs/hep-th/0311044/.^ I’m aware of the species problem; in fact Ted Jacobson has a good paper on why it isn’t really a problem: http://arxiv.org/abs/gr-qc/9404039.
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    .Retrieved December 16, 2005.
      – A guide to the string theory literature.
  • Ajay, Shakeeb, Wieland et al.^ The fourth dimension may be seen as a pilot wave as decribed by de Broglie et al, which guides the probabilistic propagation of the particulate photon.
    • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

    ^ Aaron Bergman Says: Comment #113 December 31st, 2006 at 4:40 pm Renormalizable isn’t the word I would use for string theory.
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    ^ Greg Kuperberg Says: Comment #49 December 23rd, 2006 at 3:55 am Although string theory is mostly over my head, I have studied general relativity.
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    (2004). "The nth dimension". http://thenthdimension.com/. .Retrieved December 16, 2005.  – A comprehensive compilation of materials concerning string theory.^ Aaron Bergman Says: Comment #113 December 31st, 2006 at 4:40 pm Renormalizable isn’t the word I would use for string theory.
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    ^ Greg Kuperberg Says: Comment #49 December 23rd, 2006 at 3:55 am Although string theory is mostly over my head, I have studied general relativity.
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    ^ Scott Says: Comment #112 December 31st, 2006 at 12:13 pm String theory is renormalizable in 25+1 ordinary dimensions, or in 9+1 supersymmetric dimensions.
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    Created by an international team of students.
  • Woit, Peter (2002). ."Is string theory even wrong?".^ The former is a likely consequence of string theory — maybe even confirmed for some kinds of black holes, although I am not sure — while the latter always seemed inelegant to me.
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    ^ Nonetheless, as I understand it, t’Hooft has been saying that he would like humanity to replace not only string theory, but even quantum probability by something better.
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    ^ When I reminded him that other people complain about exaggerated claims made on string theory’s behalf, he replied that the two cases were not even remotely comparable.
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    American Scientist. .http://www.americanscientist.org/issues/pub/is-string-theory-even-wrong.^ The former is a likely consequence of string theory — maybe even confirmed for some kinds of black holes, although I am not sure — while the latter always seemed inelegant to me.
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    ^ Nonetheless, as I understand it, t’Hooft has been saying that he would like humanity to replace not only string theory, but even quantum probability by something better.
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    ^ When I reminded him that other people complain about exaggerated claims made on string theory’s behalf, he replied that the two cases were not even remotely comparable.
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    .Retrieved December 16, 2005.
      – A criticism of string theory.
  • Veneziano, Gabriele (May 2004), "The Myth of the Beginning of Time", Scientific American, http://www.sciam.com/article.cfm?chanID=sa006&articleID=00042F0D-1A0E-1085-94F483414B7F0000 
  • McKie, Robin (2006-10-09), "Setback as string theory of the universe is de-bunked" ( – Scholar search), The Hindu, http://www.hindu.com/thehindu/holnus/008200610091240.htm 
  • Harris, Richard (2006-11-07).^ Moshe Says: Comment #44 December 22nd, 2006 at 11:37 pm Another problem I have with the mental picture of locality on the horizon is the following.
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    ^ A critical density is associated with an "Einstein de Sitter Universe" for which equals 1.
    • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

    ^ Posted by Plato at Monday, January 09, 2006 0 Dialogos of Eide Labels: Collision , String Theory Links to this post .
    • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

    ."Short of 'All,' String Theorists Accused of Nothing".^ And I like getting an all-expenses-paid trip to Stanford to have a freewheeling, day-long intellectual conversation with the string theorists there.
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    National Public Radio. http://www.npr.org/templates/story/story.php?storyId=6377252. .Retrieved 2007-03-05. 
  • A website dedicated to creative writing inspired by string theory.
  • An Italian Website with various papers in English language concerning the mathematical connections between String Theory and Number Theory.
  • George Gardner (2007-01-24).^ What’s the connection to string theory?
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    ^ With string theory you can throw in a bazillion different inputs and get an infinite number of outputs, it seems like.
    • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

    ^ Fraser: Isn't that one of the thoughts that (it goes back to string theory), that gravity is so weak because it is moving between multiple dimensions?
    • Astronomy Cast - Ep. 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang 28 January 2010 0:56 UTC www.astronomycast.com [Source type: FILTERED WITH BAYES]

    "Theory of everything put to the test". tech.blorge.com. (Web link). .Retrieved on 2007-03-03.
  • Minkel, J. R. (2006-03-02), "A Prediction from String Theory, with Strings Attached", Scientific American, http://www.sciam.com/article.cfm?chanId=sa003&articleId=1475A684-E7F2-99DF-355B95296BE6031C 
  • Chalmers, Matthew (2007-09-03).^ The mass of the photon which is predicted by string theory depends on the energy of the string mode which represents the photon.
    • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

    ^ Greg Kuperberg Says: Comment #49 December 23rd, 2006 at 3:55 am Although string theory is mostly over my head, I have studied general relativity.
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    ^ Posted by Plato at Monday, January 09, 2006 0 Dialogos of Eide Labels: Collision , String Theory Links to this post .
    • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

    "Stringscape". Physics World. http://physicsworld.com/cws/article/indepth/30940. .Retrieved September 6, 2007.  — An up-to-date and thorough review of string theory in a popular way.
  • Woit, Peter.^ I have the feeling that non-renormalizability is not the only way to describe the diseases of string theory in dimensions other than 10 or 26.
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    ^ Might I use Peter Woits steadfastness to present thoughts about string theory as an example of why such atttudes would be allowed predominance and encouragement, to present the argements for, and against, as to somethings viability?
    • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

    ^ It is not, by the way satisfied in string theory, so this is one (of several) serious answers to Greg’s question of why “the topic of quantum gravity needs alternatives to string theory because…” .
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    .Not Even Wrong: The Failure of String Theory & the Continuing Challenge to Unify the Laws of Physics, 2006. ISBN 0-224-07605-1 (Jonathan Cape), ISBN 0-465-09275-6 (Basic Books)
  • Schwarz, John (2001).^ Not Even Wrong » Blog Archive » Scott Aaronson For Sale Says: Comment #7 December 21st, 2006 at 4:50 pm […] Scott Aaronson has adopted a sensible attitude towards the controversy over string theory, announcing in a new posting entitled Mercenary in the String Wars that his allegiances in this “War” are for sale to the highest bidder.
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    ^ The purpose of physics has ever been to unify and explain via deeper, fundamental, physical models, and that's what Moving Dimensions Theory provides.
    • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

    ^ Greg Kuperberg Says: Comment #49 December 23rd, 2006 at 3:55 am Although string theory is mostly over my head, I have studied general relativity.
    • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

    "Early History of String Theory: A Personal Perspective". http://online.itp.ucsb.edu/online/colloq/schwarz1/. Retrieved July 17, 2009. 

External links

.
  • Dialogue on the Foundations of String Theory at MathPages
  • Superstrings!^ Flat space string theories are 26-dimensional in the bosonic case, while superstring and M-theories turn out to involve 10 or 11 dimensions for flat solutions.
    • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

    .String Theory Home Page – Online tutorial
  • CI.physics.^ Modern financial theory as applied ranks with string theory in physics as one of the greatest intellectual frauds of our time.
    • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

    ^ Particles & Strings - an overview of the frontier of particle physics and string theory.
    • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

    ^ String Theory, Loop Quantum Gravity, and Lisi Mania are all symptoms of big-money physics.
    • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

    .STRINGS newsgroup – A moderated newsgroup for discussion of string theory (a theory of quantum gravity and unification of forces) and related fields of high-energy physics.
  • Not Even Wrong – A blog critical of string theory.
  • Superstring Theory Perimeter Institute for Theoretical Physics
  • The Official String Theory Web Site
  • The Elegant Universe – A Three-Hour Miniseries with Brian Greene by NOVA (original PBS Broadcast Dates: October 28, 8-10 p.m.^ It’s not obviously related to quantum gravity, anyway.
    • Dialogos of Eide: 01/06 20 September 2009 22:36 UTC eskesthai.blogspot.com [Source type: FILTERED WITH BAYES]

    ^ If it is true,m quantum gravity is physically meaningless.
    • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

    ^ Brian Green Gets Close Dark Energy Dark Matter Unifying Quantum Mechanics and Relativity The Purpose of Physics Predictions made by MDT Consider a four dimensional manifold wherein the fourth dimension is expanding relative to the three spatial dimensions: Such a universe would predict relativistic effects such as length contraction, time dilation, and the equivalence of mass and energy, all based on a physical model.
    • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

    and November 4, 8-9 p.m., 2003). Various images, texts, videos and animations explaining string theory.
  • Beyond String Theory – A project by a string physicist explaining aspects of string theory to a broad audience.
  • Spinning the Superweb: Essays on the History of Superstring Theory – A Science Studies' approach to the history of string theory (an elementary knowledge of string theory is required).

Study guide

Up to date as of January 14, 2010
(Redirected to String theory for undergraduates article)

From Wikiversity

.Refer to the external website http://www.superstringtheory.com/index.html for more information.^ Read more at www.newscientist.com .
  • Eyes open for Alzheimer’s 28 January 2010 0:56 UTC scify.amplify.com [Source type: General]

^ For more information or to register check www.downtownglenellyn.com .
  • string theory yarn co - a feel good yarn shop in Chicago's western suburbs 28 January 2010 0:56 UTC stringtheoryyarncompany.com [Source type: FILTERED WITH BAYES]

^ The official string theory website is at http://www.superstringtheory.com .
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

.String theory is a mathematical model in physics.^ And how has string theory changed mathematics?

^ The impact of String Theory is not just felt in physics, but also in modern mathematics.

^ String theory is a proposed physical theory.
  • Why 10 Dimensions 20 September 2009 22:36 UTC www.amitylounge.com [Source type: FILTERED WITH BAYES]

.It is still under heavy construction.^ It is still under heavy construction.
  • String theory for undergraduates - Wikiversity 20 September 2009 22:36 UTC en.wikiversity.org [Source type: FILTERED WITH BAYES]

.It is an extension of quantum field theory, which is also in many senses incomplete.^ Quantum field theory is also examined.
  • Abstracts: String instruments: string theory may soon be testable. THE STRING THEORY LANDSCAPE: the theory of strings predicts that the universe might occupy one random "valley" out of a virtually infinite selection of valleys in a vast landscape of possibilities - Science and technology 28 January 2010 0:56 UTC www.faqs.org [Source type: Academic]

^ It is an extension of quantum field theory, which is also in many senses incomplete.
  • String theory for undergraduates - Wikiversity 20 September 2009 22:36 UTC en.wikiversity.org [Source type: FILTERED WITH BAYES]

^ A quantum field theory explains the universe...
  • PhysForum Science, Physics and Technology Discussion Forums -> String Theory 28 January 2010 0:56 UTC www.physforum.com [Source type: FILTERED WITH BAYES]

The basic theme in the work of a string theorist is:
  • pick a classical space (manifold, to be specific)
  • define an action for a classical string to move in the space
  • quantize your system
  • From here you may
    • study the phenomena in it and compare what you get to the real world
    • compare your system to other mathematical structures known or unknown
.However, all these are often much easier said than done.^ However, this cell death also tends to extend to cells at the back of the eye, where it is much easier to detect abnormalities.
  • Eyes open for Alzheimer’s 28 January 2010 0:56 UTC scify.amplify.com [Source type: General]

^ These Cheese Strings are collectively known as the 12 Fundamental Cheeses , however not all have been observed in a scientific fashion (ie, whilst drinking port ).
  • String Theory - Uncyclopedia, the content-free encyclopedia 28 January 2010 0:56 UTC uncyclopedia.wikia.com [Source type: FILTERED WITH BAYES]
  • String Theory - Uncyclopedia, the content-free encyclopedia 28 January 2010 0:56 UTC mirror.uncyc.org [Source type: FILTERED WITH BAYES]

^ Even if there were a complete equation governing the behavior of strings, it's usually the case in physics that writing down an equation is much, much easier than solving it.
  • How to Understand String Theory | eHow.com 28 January 2010 0:56 UTC www.ehow.com [Source type: General]

.Quantization is often a difficult problem.^ Quantization is often a difficult problem.
  • String theory for undergraduates - Wikiversity 20 September 2009 22:36 UTC en.wikiversity.org [Source type: FILTERED WITH BAYES]

.Another fundamental problem is that, if string theory is to be a fundamental physical theory, we would really want to start from a quantum definition and derive the classical analogue, which is oppposite to what can be done at the moment.^ Quantum theory would be needed to solve these problems.
  • String Theory - The Collapse of Special Relativity 28 January 2010 0:56 UTC www.relativitycollapse.com [Source type: FILTERED WITH BAYES]

^ Quantum Theory of Tunneling Tunneling is a reality not predicted by Newtonian physics.
  • How to Understand String Theory | eHow.com 28 January 2010 0:56 UTC www.ehow.com [Source type: General]

^ What string theory is really good for .
  • String Theory [Comic] - Call of Duty 4 Forums 28 January 2010 0:56 UTC cod4boards.com [Source type: FILTERED WITH BAYES]
  • The Friend | What string theory is really good for 28 January 2010 0:56 UTC thefriend.org [Source type: FILTERED WITH BAYES]

.So we still don't know what string theory is (but see M-theory).^ So we still don't know what string theory is (but see M-theory ).
  • String theory for undergraduates - Wikiversity 20 September 2009 22:36 UTC en.wikiversity.org [Source type: FILTERED WITH BAYES]

^ Still don't know who the culprit was...
  • Dolittler: String theory for pets (or, how to handle linear foreign bodies) 28 January 2010 0:56 UTC www.dolittler.com [Source type: General]

^ String theory for undergraduates [ edit ] See also .
  • Topic:String theory - Wikiversity 28 January 2010 0:56 UTC en.wikiversity.org [Source type: FILTERED WITH BAYES]

.Another problem is to construct a 4-dimensional model with all the particles and interactions we can observe in our accelerators.^ Another problem is to construct a 4-dimensional model with all the particles and interactions we can observe in our accelerators.
  • String theory for undergraduates - Wikiversity 20 September 2009 22:36 UTC en.wikiversity.org [Source type: FILTERED WITH BAYES]

^ One would therefore like to understand the space of all worldsheet QFTs whose effective target space geometry and particle content is close to the one experimentally observed.
  • string theory in nLab 28 January 2010 0:56 UTC ncatlab.org [Source type: Reference]

^ It has since developed into something much more ambitious: an approach to the construction of a complete unified theory of all fundamental particles and forces.
  • symmetry - May 2007 - Explain it in 60 Seconds: String Theory 28 January 2010 0:56 UTC www.symmetrymagazine.org [Source type: Academic]

.The candidate models are so numerous (the so-called "landscape") that it is almost impossible to pick out "the one" without addditional insights.^ The candidate models are so numerous (the so-called " landscape ") that it is almost impossible to pick out "the one" without addditional insights.
  • String theory for undergraduates - Wikiversity 20 September 2009 22:36 UTC en.wikiversity.org [Source type: FILTERED WITH BAYES]

^ One would almost think it impossible to make something as recondite as sting theory clear to laypeople, but Jones pulls it off with wit and panache.
  • Math.com Store: Math Books: String Theory For Dummies (For Dummies (Math & Science)) 28 January 2010 0:56 UTC store.math.com [Source type: General]

^ "Since we don't have a complete understanding of string theory, it's impossible to rule out all possible models that are based on strings," said Rothstein.
  • Physicists Develop Test for String Theory 28 January 2010 0:56 UTC www.spacedaily.com [Source type: FILTERED WITH BAYES]

.However, since the standard model predicts the Higgs bosons and string theory requires supersymmetric particles on top of that, experiments may provide new clues to another breakthrough - or resignation.^ New gTLDs String Theory for Bidders .
  • New gTLDs String Theory for Bidders 28 January 2010 0:56 UTC www.circleid.com [Source type: FILTERED WITH BAYES]

^ Superstring theory (or Supersymmetric string theory) .
  • String Theory For Dummies Cheat Sheet - For Dummies 28 January 2010 0:56 UTC www.dummies.com [Source type: FILTERED WITH BAYES]

^ However, since the standard model predicts the Higgs bosons and string theory requires supersymmetric particles on top of that, experiments may provide new clues to another breakthrough - or resignation.
  • String theory for undergraduates - Wikiversity 20 September 2009 22:36 UTC en.wikiversity.org [Source type: FILTERED WITH BAYES]

See also


Wikibooks

Up to date as of January 23, 2010
(Redirected to String Theory article)

From Wikibooks, the open-content textbooks collection

Contents

Notation

The metric has signature ( + , − , − , − ,...).
Greek letters from the middle of the alphabet (μ,ν,...) denote coordinates in spacetime. Roman letters taken from the beginning of the alphabet (a,b,...) denote coordinates on the worldsheet.
The metric is denoted gμν. In the case where there is a metric of spacetime and a metric of the worldsheet, the worldsheet metric is denoted hab
.A lower-case d is the number of dimensions.^ If we make the strings more 3-D at the start, these four graphs become only one graph, lowering the number of dimensions.
  • String theory - Science Forums 28 January 2010 0:56 UTC hypography.com [Source type: General]

An upper-class D represents the number of spacial dimensions.

Introduction

String Theory as a Theory of Everything

.In the past couple of decades, only recently were alternative thoughts of past, present, and future dimension thought to exist.^ Only the present ever exists, and the past is what is recorded in our minds-it exists nowhere else.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

^ I've done a number of recordings in the past that have all been self-released and they were great but I only sold a couple of them, gave them away mostly to friends.

^ Only a photon can exist in this dimension, orthogonal to the three dimensions, and at that point a photon is matter surfing the expanding dimension.
  • Math Forum Discussions 20 September 2009 22:36 UTC mathforum.org [Source type: FILTERED WITH BAYES]

.But as more relative physical and particle data are being discovered, more and more theories of extra dimensions, in which quantum mechanists believe alternatives live in.^ Quantum physics isn't "just a theory" .
  • String Theory Possibly Ruled Out by Accelerator 28 January 2010 0:56 UTC www.shortnews.com [Source type: General]

^ In the world of physics, String Theory is, at this moment, the most promising candidate theory for a unified description of the fundamental particles and forces in nature...

^ There are other, potentially equally promising approaches to unifying physics' two seemingly incompatible visions of the cosmos: general relativity and quantum mechanics.
  • Moving Beyond String Theory 28 January 2010 0:56 UTC www.wired.com [Source type: FILTERED WITH BAYES]

The History of String Theory

Dual Models

The First String Theory Revolution

The Second String Theory Revolution

.In the early ninties when Edward Witten unified the five String Theories and Supper Gravity into the frame work of M-Theory.^ This is where string theory comes into the picture.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ String theory’s biggest triumph is still its first one, unifying Einstein’s lordly gravity, which curves the cosmos, and the quantum pinball game of chance, which lives inside it.
  • Is String Theory About to Snap? « Not Even Wrong 28 January 2010 0:56 UTC www.math.columbia.edu [Source type: FILTERED WITH BAYES]

^ String theorists are currently working toward postulating a theory about the “spacetime singularity” of black holes that might resolve some of these mysteries.
  • SparkNotes: The Elegant Universe: Part IV: String Theory and the Fabric of Spacetime 28 January 2010 0:56 UTC www.sparknotes.com [Source type: FILTERED WITH BAYES]

Supersymmetry

Supergroups

Supersymmetric Quantum Mechanics

Supersymmetry is a fermionic extension of Poincare symmertry.

Two-Dimensional Conformal Field Theory

Conformal Transformations

The Conformal Group

.The story of string theory begins with two-dimensional conformal invariance.^ The presence of two-dimensional diffeomorphism invariance in string theory leads to the condition that c = 26.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ In other words, we have a two-dimensional conformal field theory (CFT).
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ String theory is inconsistent theory, because Lorentz invariance postulate of string theory violates the concept of hidden dimensions by definition.
  • symmetry breaking » Blog Archive » A first: String theory predicts an experimental result 28 January 2010 0:56 UTC www.symmetrymagazine.org [Source type: FILTERED WITH BAYES]

.Conformal transformations on a manifold preserve angles at every point, an example of such a transformation being the Mercator projection of the Earth onto an infinite cylinder.^ The connection is by way of model order reduction, information theory, and projection onto Kahler manifolds .
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

.They may be defined as transformations that leave the metric invariant up to a scale.^ If the state is semiclassical there is a macroscopic notion of locality defined by the metric it is semiclassical to, but this may differ from microlocality in any of the basis states in the superposition that makes the semiclassical state.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ These trends among the forming forces of nature all converge; they all converge on a point up near this plank scale I was telling you about earlier.
  • The Complete Idiot's Guide to String Theory: Scientific American Podcast 28 January 2010 0:56 UTC www.scientificamerican.com [Source type: Original source]

^ The degrees of freedom in the formulation can be reduced via the requirement of conformal invariance under the conformal transformation (Figure 01b), which rescale the world sheet metric.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

\underline{g}_{\mu 
u}(\underline{x}^\xi) = \Lambda(x^\xi) g_{\mu 
u}(x^\xi)
The set of invertable conformal transformations form a group. This is the conformal group.
.Let us apply this rule to a two dimensional manifold.^ And number two: does this theory really work in detail, when you try to apply it to the world around us?
  • Brian Greene on string theory | Video on TED.com 28 January 2010 0:56 UTC www.ted.com [Source type: Original source]
  • Brian Greene on string theory | Video on TED.com 28 January 2010 0:56 UTC live4.ted.com [Source type: Original source]

\underline{g}_{\underline{\mu} \underline{
u}}(\underline{x}^\xi) = \left ( \frac{\partial \underline{x}^\underline{\mu}}{\partial x^\mu} \right ) \left ( \frac{\partial \underline{x}^\underline{
u}}{\partial x^
u} \right ) g_{\mu 
u}(x^\xi)
For this transformation to be conformal the metrics must be proportional to one another, which means,
 \left ( \frac{\partial \underline{x}^\underline{\mu}}{\partial x^\mu} \right ) \left ( \frac{\partial \underline{x}^\underline{
u}}{\partial x^
u} \right ) \propto \delta_\mu^\underline{\mu} \delta_
u^\underline{
u}
Writing out the components, the following conditions emerge:
\left(\frac{\partial z^0}{\partial \underline{z}^0}\right)^2 + \left(\frac{\partial z^0}{\partial \underline{z}^1}\right)^2 = \left(\frac{\partial z^1}{\partial \underline{z}^0}\right)^2 + \left(\frac{\partial z^1}{\partial \underline{z}^1}\right)^2
\frac{\partial \underline{x}^0}{\partial x^0}\frac{\partial \underline{x}^1}{\partial x^0}+\frac{\partial \underline{x}^0}{\partial x^1}\frac{\partial \underline{x}^1}{\partial x^1}
.These conditions turn out to be equivalent to the Cauchy-Riemann conditions for either holomorphic or antiholomorphic functions!^ The zero-point energies associated with these two types of degrees of freedom turn out to be opposite in sign, and cancel out identically in a supersymmetric system.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ For example, if I flip two coins behind my back, you don't know how either of them turned out, so your information about the results is 0.
  • Recursivity: Stephen Meyer's Bogus Information Theory 28 January 2010 0:56 UTC recursed.blogspot.com [Source type: FILTERED WITH BAYES]

^ It turns out that physicists had already for some time been looking at these branches of algebra (the sorts of algebras first discovered in the 19th century).
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

\frac{\partial \underline{x}^1}{\partial x^0} = \frac{\partial \underline{x}^0}{\partial x^1} and \frac{\partial \underline{x}^0}{\partial x^0} = -\frac{\partial \underline{x}^1}{\partial x^1} (holomorphic)
\frac{\partial \underline{x}^1}{\partial x^0} = -\frac{\partial \underline{x}^0}{\partial x^1} and \frac{\partial \underline{x}^0}{\partial x^0} = \frac{\partial \underline{x}^1}{\partial x^1} (antiholomorphic)
.In two dimensions, therefore, the conformal group is the set of all invertable holomorphic maps, which is isomorphic to the set of all antiholomorphic maps.^ Thus, all the five string theories involve two-dimensional membranes, which become apparent in the strong coupling limit and show up in the 11th dimension.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ Indeed, in all the closed string theories (type IIA, IIB and the two heterotic strings) the fundamental string carries unit charge under B and is therefore guaranteed to be stable.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

^ So far we discussed two possible boundary conditions: Neumann in all 9 directions, or Dirichlet in all 9 dimensions.
  • The Theory of Strings: A Detailed Introduction: Sunil Mukhi 28 January 2010 0:56 UTC theory.tifr.res.in [Source type: FILTERED WITH BAYES]

.For this reason it is convenient to use complex coordinates when discussing two-dimensional conformal fields.^ In other words, we have a two-dimensional conformal field theory (CFT).
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ Although superstrings are formulated in a ten-dimensional space-time, in another sense a string field is also a theory about two-dimensional surfaces.
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ The spacetime metric acts like `coupling constants' on the two-dimensional fields.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

The set of all reversible holomorphic functions is the set of fractional linear transformations
f(z) = \frac{\heartsuit z - \clubsuit }{ \spadesuit z + \diamondsuit}
where
\heartsuit \diamondsuit - \clubsuit \spadesuit = 1
It is easily verified by composing two such functions that their composition is equivalent to matrix multiplication for matrices of the form
\begin{pmatrix} \heartsuit & \clubsuit \\ \spadesuit & \diamondsuit \end{pmatrix}
.It is clear that the conformal group in two dimensions is equivalent to the group of complex invertible 2	imes2 matrices having a determinate of 1. This group is also known as SL(2,\mathbb{C}).^ The charges of all known particles can be plotted in a four-dimensional charge space, and projected down to two dimensions like this so we can see them.
  • Garrett Lisi on his theory of everything | Video on TED.com 28 January 2010 0:56 UTC www.ted.com [Source type: FILTERED WITH BAYES]

The Virasoro Algebra

Modular Invariance

Superconformal Transformations

Classical Strings

The Classical String

.Let us embed an action that is conformally invariant in two dimensions into a higher dimensional space.^ Rather than imagine that the extra dimensions are very small, one can imagine that they are much larger and we live on a (3 + 1)-dimensional brane in this higher dimensional space.
  • Spacetime in string theory 28 January 2010 0:56 UTC www.iop.org [Source type: Academic]

^ I won’t feel like I have any handle on this quantum-gravity business until I understand why the 2+1-dimensional case is so different from the case of 3+1 and higher dimensions.
  • Shtetl-Optimized » Blog Archive » Mercenary in the String Wars 28 January 2010 0:56 UTC scottaaronson.com [Source type: FILTERED WITH BAYES]

^ We need convenient labels to define the spatial dimensions these strings occupy, so let us say that hadron strings locate their volume in "hadron space," and lepton strings locate their volume in "lepton space."
  • Nuclear Geometry: String Basics 28 January 2010 0:56 UTC www.stringtheory.com [Source type: Original source]

.We will find that such an action generalizes the concept of the point particle.^ String theory, which took off in 1984, posits that elementary particles such as electrons are not points, as standard physics had it.
  • Has String Theory Tied Up Physics? - WSJ.com 28 January 2010 0:56 UTC online.wsj.com [Source type: General]

^ Construction of the superstring theory starts with the " Action Principle ", which confines the movement of the string such that the world sheet sweeps out a minimum area (similar to the shorest distance for the case of point particle).
  • Superstring Theory 28 January 2010 0:56 UTC universe-review.ca [Source type: FILTERED WITH BAYES]

^ Hawking said we'd need a particle accellerator equivalent to the Earth's orbit to generate sufficient energy for such observations.
  • Evidence for String Theory!! - JREF Forum 28 January 2010 0:56 UTC forums.randi.org [Source type: FILTERED WITH BAYES]

Boundary Conditions

The Classical Superstring

Two-Dimensional Quantum Field Theory

here goes

Quantum Conformal Fields

The Stress Tensor

Quantum Superconformal Fields

BRST Ghosts

Conformal Ghosts

Superconformal Ghosts

String Quantization

Light-Cone Strings

Covariant Strings

BRST Covariant Strings

The Free String

The Bosonic String Theory

The Superstring Theories

The Heterotic String Theories

String Interactions

String Field Theory

Compactification

Orbifolds and Orientifolds

T-Duality

D-branes

M-Theory


Simple English


String theory is the name for a number of mathematical models that want to find a common explanation for the four main forces that have so far been observed in nature. These forces are gravity, the electromagnetic force, the strong nuclear force and the weak nuclear force, respectively.

Classical physics says that the universe is made of small particles (points) which are basically static and unchanging. String theory says that the particle is a string/line (not a particle/point) that forms these four different forces by vibrating in different ways.

String Theory suggests that the universe is similar to a very big guitar. The strings upon the guitar are one dimensional and vibrate to take the form of all matter and stuff.

Main idea

Usually, scientists think of matter as being made of very, very small particles. These particles are so small (much smaller than an atom) that we cannot observe them to see their shape. At this time, all mathematical formulas say that the particles are point-like and therefore have no shape at all. The main idea behind string theory is that this is wrong, and that these small particles are instead shaped as tiny loops of string.

The theory imagines that these strings are not precise particles (unlike things that are seen and counted). The strings are very small, yet they seem to act like regular particles. It explains how other particles and forces act. Because they are so small their actual shape does not matter much when we are looking at larger objects.

String theory suggests that when these tiny loops move really, really fast back and forth in different and diverse ways, they are actually a different type of matter. In other words, if the string theory loop oscillates in one way it becomes a different type of matter than if it oscillates in another way (these changes in oscillation can be hard to detect, as the "strings" are oscillating in at least 10 different dimensions).

Status

It is used as a possible way of explaining how some things work; it is very hard for scientists to prove everything, or answer every question that they can imagine by using just one theory on its own. String Theory is slightly different from most other theories because it could help scientists get closer to explaining everything that they can think of, so many scientists are excited by the ideas that String Theory has to offer. It could someday be a "Theory of Everything", something that scientists such as Albert Einstein had been dreaming of for a very long time.

There are two ideas that predict the same physical observations of the whole universe. One is "as large as we think the universe is", about the 74 billion light years circumference predicted in Weeks' model. The other is much smaller than the Planck Length. Both mathematics are just as good to explain what we can see.

There are several different versions of string theory as well. The Superstring theory is based on 10 or 11 dimensions. The Bosonic string theory has 26 dimensions. Gravity is the only real force in the theory. It says only four of the ten dimensions can be observed by us, and that the others hint at the other forces that are observed. It does not say that other physics theories are not true, or wrong.

String theory has led to many new ideas in the mathematics of folding, knots and Calabi-Yau spaces.

Problems

There are many different versions of string theory, and none of them are fully accurate. Often, many of them use only good guesses. String theory proponents say this is because the theory is not finished yet.

Another problem is that the mathematical laws of string theory also give lots of different possible solutions. Scientists that believe in string theory work around this problem by picking only the results that match our observations and saying that later we will find why the other ones are not good. Opponents argue that we can not ever know if a theory is true as a whole if we only take the bits that work. This also makes the theory of little use until the issue is solved, because mathematical laws are usually used to predict what will happen in a situation - but string theory cannot yet answer that question, because it needs to be tried first and then scientists can pick the answers that work.

Yet another problem is that it says our universe is made of at least 10 dimensions, while we only see four (width, height, depth, time). String theory proponents say some dimensions may not be visible to us, but others doubt there can be 6 or more hidden dimensions, or that we will never be able to access them even if they do exist.

String theory does not make guesses that can actually be tested by scientists today or in the near future. Some people say this makes the theory unscientific.


Citable sentences

Up to date as of December 18, 2010

Here are sentences from other pages on String theory, which are similar to those in the above article.








Got something to say? Make a comment.
Your name
Your email address
Message