Bulletin of the
Korean Mathematical Society
BKMS

ISSN(Print) 1015-8634 ISSN(Online) 2234-3016

Article

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Bull. Korean Math. Soc. 2023; 60(3): 637-647

Online first article May 11, 2023      Printed May 31, 2023

https://doi.org/10.4134/BKMS.b220041

Copyright © The Korean Mathematical Society.

Characterization of weakly cofinite local cohomology modules

Moharram Aghapournahr, Marziye Hatamkhani

Arak University; Arak University

Abstract

Let $R$ be a commutative Noetherian ring, $\mathfrak{a}$ an ideal of $R$,
$M$ an arbitrary $R$-module and $X$ a finite $R$-module. We prove a characterization  for ${H} \DeclareMathOperator{\End}{End}_{\mathfrak{a}}^{i}(M)$ and ${H} \DeclareMathOperator{\End}{End}_{\mathfrak{a}}^{i}(X,M)$ to be $\mathfrak{a}$-weakly cofinite for all $i$, whenever one of the following cases holds:
(a) ${ara} (\mathfrak{a})\leq 1$, (b) $\dim R/\mathfrak{a} \leq 1$ or (c) $\dim R\leq 2$. We also
prove that, if $M$ is a weakly Laskerian $R$-module, then ${H} \DeclareMathOperator{\End}{End}_{\mathfrak{a}}^{i}(X,M)$ is $\mathfrak{a}$-weakly cofinite for all $i$, whenever $\dim X\leq 2$ or $\dim M\leq 2$ (resp.$(R,\mathfrak{m})$ a local ring and $\dim X\leq 3$ or $\dim M\leq 3$).  Let $d=\dim M<\infty$, we prove an equivalent condition for top local cohomology module ${H} \DeclareMathOperator{\End}{End}_{\mathfrak{a}}^{d}(M)$ to be weakly Artinian.

Keywords: Local cohomology, weakly cofinite modules, weakly Laskerian modules

MSC numbers: Primary 13D45, 14B15, 13E05