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Trivial action on the tensor product of finite groups

Published online by Cambridge University Press:  18 May 2009

R. J. Higgs
Affiliation:
Department of Mathematics, University College, Dublin 4, Ireland.
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Let G, H and K be finite groups such that K acts on both G and H. The action of K on G and H induces an action of K on their tensor product G ⊗ H, and we shall denote the K-stable subgroup of GH by (GH)K. In section 1 of this note we shall obtain necessary and sufficient conditions for (GH)K = GH. The importance of this result is that the direct product of G and H has Schur multiplier M(G × H) isomorphic to M(G) × M(H) × (GH); moreover K: acts on M(G × H), and M(G × H)K is one of the terms contained in a fundamental exact sequence concerning the Schur multiplier of the semidirect product of K and G × H (see [3, (2.2.10) and (2.2.5)] for details). Indeed in section 2 we shall assume that G is abelian and use the fact that M(G) ≅ GG to find necessary and sufficient conditions for M(G)K = M(G).

Type
Research Article
Copyright
Copyright © Glasgow Mathematical Journal Trust 1988

References

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