English

Faltings' Local-global Principle and Annihilator Theorem for the finiteness dimensions

Commutative Algebra 2018-01-03 v2

Abstract

Let RR be a commutative Noetherian ring, MM a finitely generated RR-module and nn be a non-negative integer. In this article, it is shown that there is a finitely generated submodule NiN_i of Hai(M)H_{\frak a}^i(M) such that dimSuppHai(M)/Ni<n\dim{\rm Supp } H_{\frak a}^i(M)/N_i<n for all i<ti<t if and only if there is a finitely generated submodule Ni,pN_{i,{\frak p}} of HaRpi(Mp)H_{{\frak a} R_{\frak p}}^i(M_{\frak p}) such that dimSuppHaRpi(Mp)/Ni,p<n\dim{\rm Supp } H_{{\frak a} R_{\frak p}}^i(M_{\frak p})/N_{i,{\frak p}}<n for all i<ti<t. This generalizes Faltings' Local-global Principle for the finiteness of local cohomology modules (Faltings' in Math. Ann. 255:45-56, 1981). Also, it is shown that whenever RR is a homomorphic image of a Gorenstein local ring, then the invariants inf{iN0dimSupp(btHai(M))n for all tN0}\inf\{i\in\mathbb N_0\mid\dim{\rm Supp}({\frak b}^tH_{\frak a}^i(M))\geq n\text{ for all } t\in\mathbb N_0\} and inf{depthMp+ht(a+p)/ppSpecRV(b) and dimR/(a+p)n}\inf\{{\rm depth } M_{\frak p}+{\rm ht}({\frak a}+{\frak p})/{\frak p}\mid{\frak p}\in{\rm Spec } R\setminus V({\frak b}) \text{ and } \dim R/({\frak a}+{\frak p})\geqslant n\} are equal, for every finitely generated RR-module MM and for all ideals a,b\frak a, \frak b of RR with ba{\frak b}\subseteq {\frak a}. As a consequence, we determine the least integer ii where the local cohomology module Hai(M)H_{\frak a}^i(M) is not minimax (resp. weakly laskerian).

Keywords

Cite

@article{arxiv.1712.09067,
  title  = {Faltings' Local-global Principle and Annihilator Theorem for the finiteness dimensions},
  author = {Mohammad Reza Doustimehr},
  journal= {arXiv preprint arXiv:1712.09067},
  year   = {2018}
}