Bulletin of the
Korean Mathematical Society
BKMS

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

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Bull. Korean Math. Soc. 2013; 50(2): 649-657

Printed March 31, 2013

https://doi.org/10.4134/BKMS.2013.50.2.649

Copyright © The Korean Mathematical Society.

Finiteness properties of extension functors of cofinite modules

Yavar Irani and Kamal Bahmanpour

Islamic Azad University Meshkin-Shahr branch, Islamic Azad University-Ardabil branch

Abstract

Let $R$ be a commutative Noetherian ring, $I$ an ideal of $R$ and $T$ be a non-zero $I$-cofinite $R$-module with $\dim(T)\leq 1$. In this paper, for any finitely generated $R$-module $N$ with support in $V(I)$, we show that the $R$-modules $\Ext^i_R(T,N)$ are finitely generated for all integers $i\geq 0$. This immediately implies that if $I$ has dimension one (i.e., $\dim R/I=1$), then ${\rm Ext}^i_R(H^{j}_{I}(M),N)$ is finitely generated for all integers $i,j\geq0$, and all finitely generated $R$-modules $M$ and $N$, with $\Supp(N)\subseteq V(I)$.

Keywords: arithmetic rank, cofinite modules, local cohomology, minimax modules

MSC numbers: 13D45, 14B15, 13E05