Bourbaki

Example

Tag 0DK1, permanent. Cite it as [Bourbaki, Tag 0DK1].

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

Let BB be an algebra over the ring AA, such that BB is a free AA-module of finite dimension nn. Then the mapping (x,y)→TrB/A(xy)(x, y) \to \mathrm{Tr}_{B/A}(xy) (Chapter VIII, § 12, no 2) is a bilinear form on BB. Given a system (x1,…,xn)(x_1, \ldots, x_n) of nn elements of BB, the discriminant of this form with respect to this system is called the discriminant of the system (x1,…,xn)(x_1, \ldots, x_n) over AA, and is denoted by DB/A(x1,…,xn)D_{B/A}(x_1, \ldots, x_n). Thus

DB/A(x1,…,xn)=det⁡(TrB/A(xixj)). D_{B/A}(x_1, \ldots, x_n) = \det (\mathrm{Tr}_{B/A}(x_ix_j)).

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

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