# Kirby–Siebenmann class

Jump to: navigation, search

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.