Lemmas in algebra | Homological algebra | Representation theory

Shapiro's lemma

In mathematics, especially in the areas of abstract algebra dealing with group cohomology or relative homological algebra, Shapiro's lemma, also known as the Eckmann–Shapiro lemma, relates extensions of modules over one ring to extensions over another, especially the group ring of a group and of a subgroup. It thus relates the group cohomology with respect to a group to the cohomology with respect to a subgroup. Shapiro's lemma is named after Arnold S. Shapiro, who proved it in 1961; however, Beno Eckmann had discovered it earlier, in 1953. (Wikipedia).

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Related pages

Group ring | Subgroup | Abstract algebra | Change of rings | Hom functor | Mathematics | Induced representation | Restricted representation | Ring homomorphism | Tensor product | Frobenius reciprocity | Index of a subgroup | Group (mathematics) | Group cohomology