Bourbaki

Proposition 3

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

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

Let A be a noetherian local ring and M a nonzero finite a-module. For an element x of mAm_A to be secant for M, it is necessary and sufficient that it belong to none of the minimal elements pp of Supp(M)\mathrm{Supp}(M) such that dim⁡(A/p)=dim⁡A(M)\dim(A/p) = \dim_A(M), and it is sufficient that the homothety xMx_M of ratio x in M be injective. Let α\alpha be the annihilator of M. To say that x is secant for M means that x is secant for A/αA/\alpha; the support of M consists of the prime ideals pp of A such that α⊂p\alpha \subset p; and if xMx_M is injective, the image of x in A/αA/\alpha is not a divisor of 0 in A/αA/\alpha. Proposition 3 then follows from Corollary 2 of Proposition 2 of No. 1 applied to the ring A/αA/\alpha.

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

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