Bourbaki

Corollary

Tag 0051, permanent. Cite it as [Bourbaki, Tag 0051].

Algebra, VIII, p. 70, § 4. Semisimple Modules

Let M be a semisimple A-module. For every submodule N of M and every element λ\lambda of S\mathscr{S}, identify HomA(Sλ,N)_A(S_{\lambda},N) with the DλD_{\lambda}-linear subspace of HomA(Sλ,M)_A(S_{\lambda},M) consisting of the mappings with image contained in N.

a) The mapping N↦N\mapsto (HomA(Sλ,N)_A(S_{\lambda},N))λ∈S_{\lambda\in\mathscr{S}} is a bijection from the set of A-submodules of M to the set of families (Wλ)λ∈S(W_{\lambda})_{\lambda\in\mathscr{S}} such that for every λ∈S\lambda \in \mathscr{S}, WλW_{\lambda} is a DλD_{\lambda}-linear subspace of HomA(Sλ,M)_A(S_{\lambda},M).

b) The inverse bijection sends a family (Wλ)λ∈S(W_{\lambda})_{\lambda\in\mathscr{S}} to the A-submodule ∑λ∈S∑w∈Wλw(Sλ)\sum_{\lambda\in\mathscr{S}}\sum_{w\in W_{\lambda}}w(S_{\lambda}) of M.

This is a reformulation of Proposition 8, c) applied to the canonical description of M.

Bourbaki sets the proof directly after the statement, and the corpus does not separate them, so what is above is the statement and its proof together.

Cited by

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Cites

Transcribed from the printed edition, 2023, Springer Nature. Not translated.