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# Kirby–Siebenmann class: Wikis

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# Encyclopedia

Updated live from Wikipedia, last check: May 20, 2013 18:51 UTC (43 seconds ago)

In mathematics, the Kirby–Siebenmann class is an element of the fourth cohomology group

$e(M) \in H^4(M;\mathbf{Z}_2)$

which must vanish if a topological manifold M is to have a piecewise linear structure. It is named for Robion Kirby and Larry Siebenmann.