Pontryagin cohomology operation

In mathematics, a Pontryagin cohomology operation is a cohomology operation taking cohomology classes in H2n(X,Z/prZ) to H2pn(X,Z/pr+1Z) for some prime p. When p=2 these operations were introduced by Pontryagin (1942) and were named Pontryagin squares by Whitehead (1949). They were generalized to arbitrary primes by Thomas (1956).

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