Bourbaki

Corollary 2

Tag 05N7, permanent. Cite it as [Bourbaki, Tag 05N7].

Algebra, chapter II, § 2. Modules of linear mappings. Duality

Let C be a commutative ring and E, F two finitely generated projective C-modules; then Hom⁡C(E,F)\operatorname{Hom}_C(E, F) is a finitely generated projective C-module.

It may be assumed that there are two finitely generated free C-modules M, N such that M=E⊕E′,N=F⊕F′M = E \oplus E', N = F \oplus F'; it follows from § 1, no. 6, Corollary 1 to Proposition 6 that Hom⁡C(M,N)\operatorname{Hom}_C(M, N) is finitely generated and free and on the other hand that Hom⁡C(M,N)\operatorname{Hom}_C(M, N) is isomorphic to

Hom⁡C(E,F)⊕Hom⁡C(E′,F)⊕Hom⁡C(E,F′)⊕Hom⁡(E′,F′), \operatorname{Hom}_C(E, F) \oplus \operatorname{Hom}_C(E', F) \oplus \operatorname{Hom}_C(E, F') \oplus \operatorname{Hom}(E', F'),

whence the corollary.

Bourbaki puts the proof directly after the statement, so what is above is the statement and its proof together.

Cited by

Nothing.

Cites

Transcribed from the printed edition, 1998, Springer. Not translated.