English

Lower bounds of certain general local cohomology modules

Commutative Algebra 2019-09-24 v1 Algebraic Geometry

Abstract

Let RR be a commutative Noetherian ring, Φ\Phi a system of ideals of RR, \faΦ\fa \in \Phi, MM an arbitrary RR-module and tt a non-negative integer. Let S\mathcal{S} be a Melkersson subcategory of RR-modules. Among other things, we prove that if \lcΦi(M)\lc^{i}_\Phi(M) is in S\mathcal{S} for all i<ti < t then \lc\fai(M)\lc^{i}_\fa(M) is in S\mathcal{S} for all i<ti < t and for all \faΦ\fa \in \Phi. If S\mathcal{S} is the class of RR-modules NN with dimNk\dim N \leq k where k1k \geq -1, is an integer, then \lcΦi(M)\lc^{i}_\Phi(M) is in S\mathcal{S} for all i<ti < t (if and only if) \lc\fai(M)\lc^{i}_\fa(M) is in S\mathcal{S} for all i<ti < t and for all \faΦ\fa \in \Phi. As consequences we study and compare vanishing, Artinianness and support of general local cohomology and ordinary local cohomology supported at ideals of its system of ideals at initial points i<ti <t. We show that \SuppR(\lcΦdimM1(M))\Supp_{R}(\lc^{\dim M-1}_{\Phi}(M)) is not necessarily finite whenever (R,\fm)(R,\fm) is local and MM a finitely generated RR-module.

Keywords

Cite

@article{arxiv.1909.10186,
  title  = {Lower bounds of certain general local cohomology modules},
  author = {Mahmoud Behrouzian and Moharram Aghapournahr},
  journal= {arXiv preprint arXiv:1909.10186},
  year   = {2019}
}

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14 pages