In mathematics, more specifically in geometric topology, the Kirby–Siebenmann class is an obstruction for topological manifolds to allow a PL-structure. == The KS-class == For a topological manifold M, the Kirby–Siebenmann class κ ( M ) ∈ H 4 ( M ; Z / 2 ) {\displaystyle \kappa (M)\in H^{4}(M;\mathbb {Z} /2)} is an element of the fourth cohomology group of M that vanishes if M admits a piecewise linear structure.
In mathematics, more specifically in geometric topology, the Kirby–Siebenmann class is an obstruction for topological manifolds to allow a PL-structure. == The KS-class == For a topological manifold M, the Kirby–Siebenmann class κ ( M ) ∈ H 4 ( M ; Z / 2 ) {\displaystyle \kappa (M)\in H^{4}(M;\mathbb {Z} /2)} is an element of the fourth cohomology group of M that vanishes if M admits a piecewise linear structure.
Source: Wikipedia "Kirby–Siebenmann class" · CC BY-SA 4.0
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