English

A criterion for cofiniteness of modules

Commutative Algebra 2022-01-13 v1

Abstract

Let AA be a commutative noetherian ring, a\frak a be an ideal of AA, m,nm,n be non-negative integers and let MM be an AA-module such that \ExtAi(A/a,M)\Ext^i_A(A/\frak a,M) is finitely generated for all im+ni\leq m+n. We define a class \cSn(a)\cS_n(\frak a) of modules and we assume that Has(M)\cSn(a)H_{\frak a}^s(M)\in\cS_{n}(\frak a) for all sms\leq m. We show that Has(M)H_{\frak a}^s(M) is a\frak a-cofinite for all sms\leq m if either n=1n=1 or n2n\geq 2 and \ExtAi(A/a,Hat+si(M))\Ext_A^{i}(A/\frak a,H_{\frak a}^{t+s-i}(M)) is finitely generated for all 1tn11\leq t\leq n-1, it1i\leq t-1 and sms\leq m. If AA is a ring of dimension dd and M\cSn(a)M\in\cS_n(\frak a) for any ideal a\frak a of dimension d1\leq d-1, then we prove that M\cSn(a)M\in\cS_n(\frak a) for any ideal a\frak a of AA.

Keywords

Cite

@article{arxiv.2201.04251,
  title  = {A criterion for cofiniteness of modules},
  author = {Mohammad Khazaei and Reza Sazeedeh},
  journal= {arXiv preprint arXiv:2201.04251},
  year   = {2022}
}
R2 v1 2026-06-24T08:47:10.637Z