Bourbaki

Example

Tag 0DK4, permanent. Cite it as [Bourbaki, Tag 0DK4].

Algebra, chapter IX, § 2. Discriminant d'une forme sesquilinéaire

Let BB be an algebra over AA which is a free AA-module of finite dimension nn, (x1,…,xn)(x_1, \ldots, x_n) a basis of BB over AA, and mm an ideal of AA. If hh denotes the canonical homomorphism of BB onto B/mBB/mB, (h(x1),…,h(xn))(h(x_1), \ldots, h(x_n)) is a basis of B/mBB/mB over A/mA/m (chap. I, § 6, no 5, prop. 5), and B/mBB/mB is isomorphic to (A/m)⊗AB(A/m) \otimes_A B. We therefore have

D(B/mB)/(A/m)(h(x1),…,h(xn))=h(DB/A(x1,…,xn)). D_{(B/mB)/(A/m)}(h(x_1), \ldots, h(x_n)) = h(D_{B/A}(x_1, \ldots, x_n)).

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

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