English

On the second cohomology of semidirect products

Group Theory 2007-07-03 v1

Abstract

Let GG be a group which is the semidirect product of a normal subgroup NN and a subgroup TT, and let MM be a GG-module with not necessarily trivial GG-action. Then we embed the simultaneous restriction map res=(resNG,resTG)t:H2(G,M)H2(N,M)T×H2(T,M)res=(res^G_N,res^G_T)^t : H^2(G,M) \to H^2(N,M)^T \times H^2(T,M) into a natural five term exact sequence consisting of one and two-dimensional cohomology groups of the factors NN and TT. The elements of H2(G,M)H^2(G,M) are represented in terms of group extensions of GG by MM constructed from extensions of NN and TT.

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Cite

@article{arxiv.0707.0291,
  title  = {On the second cohomology of semidirect products},
  author = {Manfred Hartl and Sébastien Leroy},
  journal= {arXiv preprint arXiv:0707.0291},
  year   = {2007}
}

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15 pages