Library / Algebra / Chapter III / § 10
Proposition 6
Tag 066N, permanent. Cite it as [Bourbaki, Tag 066N].
Algebra, chapter III, § 10. Derivations
*Suppose that A \mathbf{A} A is a unital associative graded K \mathbf{K} K -algebra and E \mathbf{E} E a graded ( A , A ) (\mathbf{A}, \mathbf{A}) ( A , A ) -bimodule. If d : A → E d : \mathbf{A} \to \mathbf{E} d : A → E is an ε \varepsilon ε -derivation of degree δ \delta δ , then, for every finite sequence ( x i ) 1 ≤ i ≤ n (x_i)_{1 \leq i \leq n} ( x i ) 1 ≤ i ≤ n of homogeneous elements of A \mathbf{A} A , of respective degrees ξ i \xi_i ξ i (1 ≤ i ≤ n 1 \leq i \leq n 1 ≤ i ≤ n ),
d ( x 1 x 2 … x n ) = ∑ i = 1 n ε δ , ξ 1 + ⋯ + ξ i − 1 x 1 ⋯ x i − 1 ( d x i ) x i + 1 ⋯ x n .
d(x_1 x_2 \ldots x_n) = \sum_{i=1}^n \varepsilon_{\delta, \xi_1 + \cdots + \xi_{i-1}} x_1 \cdots x_{i-1} (dx_i) x_{i+1} \cdots x_n.
d ( x 1 x 2 … x n ) = i = 1 ∑ n ε δ , ξ 1 + ⋯ + ξ i − 1 x 1 ⋯ x i − 1 ( d x i ) x i + 1 ⋯ x n . Formula (21) is trivial for
n = 0 n = 0 n = 0 and is proved by induction on
n n n , taking account of (4) (no. 2).
Bourbaki puts the proof directly after the statement, so what is above is the statement and its proof together.
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Transcribed from the printed edition, 1998, Springer. Not translated.