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A particular case of the intersection's dimension conjecture

(Anne-Marie Simon)

Let a,b be two ideals of a noetherian local ring (R,m,k) such that the ideal
a+b is m-primary. It can happen that dimR/a+dimR/b > dimR, but it has
been conjectured that this is not the case when there is a finitely generated
module M of finite projective dimension, annihilated by the ideal a, with
dimM = dimR/a.

We strengthen the condition on R/a and prove the formula dimR/a+dimR/b
£ dimR when the local ring R contains a field
and when the ring R/a has a canonical module of finite injective dimension
over R (thus forcing the ring R to be Cohen-Macaulay).

Not surprisingly, one of the key points in this proof is the improved new
intersection theorem, valid in this case.

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