Bourbaki

Proposition 7

Tag 066P, permanent. Cite it as [Bourbaki, Tag 066P].

Algebra, chapter III, § 10. Derivations

Suppose that AA is a unital associative graded algebra and EE a graded (A,A)(A, A)-bimodule. Let d:A→Ed : A \to E be an ε\varepsilon-derivation of degree δ\delta and aa a homogeneous element of ZεZ_\varepsilon of degree α\alpha. Then the mapping x↦a(dx)x \mapsto a(dx) is an ε\varepsilon-derivation of degree δ+α\delta + \alpha.

We write d′(x)=a(dx)d'(x) = a(dx); for xx homogeneous of degree ξ\xi in AA and y∈Ay \in A, by virtue of (23) and (1) (no. 1),

d′(xy)=a((dx)y)+εδ,ξa(x(dy))=(a(dx))y+εδ+α,ξ(xa)(dy)=(d′x)y+εδ+α,ξx(d′y). d'(xy) = a((dx)y) + \varepsilon_{\delta, \xi} a(x(dy)) = (a(dx))y + \varepsilon_{\delta+\alpha, \xi}(xa)(dy) = (d'x)y + \varepsilon_{\delta+\alpha, \xi} x(d'y).

Proposition 7 says that the K-module of ε\varepsilon-derivations of AA into EE is a graded ZεZ_\varepsilon-module of type Δ\Delta.

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

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Cites

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