Bourbaki

Corollary 2

Tag 0D0D, permanent. Cite it as [Bourbaki, Tag 0D0D].

Commutative Algebra, chapter X, § 1. Profondeur

Let AA be a local ring, CC a complex of AA-modules bounded to the left, pp an integer. Suppose that for m≥pm \geq p, Hm(C)H_m(C) is of finite length and CmC_m of depth >m−p> m - p. Then Hn(C)=0H_n(C) = 0 for n≥pn \geq p.

The AA-module ⨁m≥pHm(C)\bigoplus_{m \geq p} H_m(C) is of finite length. Let JJ denote its annihilator; by A, VIII, § 1, No. 3, corollary, the ring A/JA/J is artinian, hence JJ contains a power of the maximal ideal of AA (A, VIII, § 10, No. 1, th. 1). It follows that prof⁡A(J;Cm)≥prof⁡(Cm)>m−p\operatorname{prof}_A(J; C_m) \geq \operatorname{prof}(C_m) > m - p for m≥pm \geq p (No. 1, cor. 1 of prop. 2), so that one may apply cor. 1.

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

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