Crossed extensions

Ratcliffe, John G.

doi:10.1090/S0002-9947-1980-0549155-0

Crossed extensions
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by John G. Ratcliffe PDF

Trans. Amer. Math. Soc. 257 (1980), 73-89 Request permission

Abstract:

We develop a natural five term exact sequence relating the second and third cohomology of groups. We show that this sequence is the proper framework for the problem of realizing an abstract kernel. As an application, we give an interpretation of the third cohomology of a group in terms of crossed sequences.

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