English

On the intersection of Annihilator of the Valabrega-Valla module

Commutative Algebra 2013-02-07 v1

Abstract

Let (A,\m)(A,\m) be a \CM \ local ring with an infinite residue field and let II be an \m\m-primary ideal. Let \bx=x1,,xr\bx = x_1,\ldots,x_r be a AA-superficial sequence \wrt \ II. Set \VcI(\bx)=n1In+1(\bx)\bxIn.\Vc_I(\bx) = \bigoplus_{n\geq 1} \frac{I^{n+1}\cap (\bx)}{\bx I^n}. A consequence of a theorem due to Valabrega and Valla is that \VcI(\bx)=0\Vc_I(\bx) = 0 \ff \ the initial forms x1,,xrx_1^*,\ldots,x_r^* is a GI(A)G_I(A) regular sequence. Furthermore this holds if and only if \depthGI(A)r\depth G_I(A) \geq r. We show that if \depthGI(A)<r\depth G_I(A) < r then \afr(I)=\bx=x1,,xr is aA-superficial sequence w.r.t I\annA\VcI(\bx) is \m-primary. \af_r(I)= \bigcap_{\substack{\text{$\bx = x_1,\ldots,x_r$ is a} \\ \text{$A$-superficial sequence w.r.t $I$}}} \ann_A \Vc_I(\bx) \quad \ \text{is} \ \m\text{-primary}. Suprisingly we also prove that under the same hypotheses, n1\afr(In) is also \m-primary. \bigcap_{n\geq 1} \af_r(I^n) \quad \ \text{is also} \ \m\text{-primary}.

Keywords

Cite

@article{arxiv.1302.1307,
  title  = {On the intersection of Annihilator of the Valabrega-Valla module},
  author = {Tony J. Puthenpurakal},
  journal= {arXiv preprint arXiv:1302.1307},
  year   = {2013}
}