Bourbaki

Corollary 1

Tag 0439, permanent. Cite it as [Bourbaki, Tag 0439].

Commutative Algebra, chapter I, § 2. Flat modules

Let A, B be two commutative rings, p:A→Bp : A \to B a homomorphism such that B is a flat A-module and E a finitely presented A-module. For every finitely generated submodule F of E, the submodule of the dual of E(B)E_{(B)} orthogonal to F(B)F_{(B)} is equal to (F′)(B)(F')_{(B)}, where F′F' is the submodule of the dual E∗E^* of E orthogonal to F.

By Proposition 11 (E∗)(B)(E^*)_{(B)} is canonically isomorphic to the dual (E(B))∗(E_{(B)})^* of E(B)E_{(B)}. Then it suffices to apply Proposition 12 with E1=E∗E_1 = E^*, E2=EE_2 = E, E3=AE_3 = A, F2=FF_2 = F, F3={0}F_3 = \{0\}, and ff the canonical bilinear form on E∗×EE^* \times E.

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 volume. Not translated.