Bourbaki

Corollary 2

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

Commutative Algebra, chapter VIII, § 3. Dimension des anneaux noethériens

Let A be a noetherian local ring, M a nonzero finitely generated A-module and α\alpha a subset of mAm_A, stable under addition and multiplication and such that long⁡(M/αM)<+∞\operatorname{long}(M/\alpha M) < +\infty. There exists a subset of α\alpha which is a maximal secant subset for M.

In fact, one has V(α)∩Supp⁡(M)=Supp⁡(M/αM)={mA}V(\alpha) \cap \operatorname{Supp}(M) = \operatorname{Supp}(M/\alpha M) = \{m_A\} (§ 1, No. 4, Remark 1), hence codim⁡(V(α)∩Supp⁡(M),Supp⁡(M))=dim⁡(Supp⁡(M))=dim⁡A(M)\operatorname{codim}(V(\alpha) \cap \operatorname{Supp}(M), \operatorname{Supp}(M)) = \dim(\operatorname{Supp}(M)) = \dim_A(M), and Proposition 9 is applied.

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

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