Rings for which every cosingular module is discrete

Year 2020, Volume: 49 Issue: 5, 1635 - 1648, 06.10.2020

Yahya Talebi , Ali Reza Moniri Hamzekolaee , Abdullah Harmancı , Burcu Üngör

https://doi.org/10.15672/hujms.500759

Abstract

In this paper we introduce the concepts of $CD$-rings and $CD$-modules. Let $R$ be a ring and $M$ be an $R$-module. We call $R$ a $CD$-ring in case every cosingular $R$-module is discrete, and $M$ a $CD$-module if every $M$-cosingular $R$-module in $\sigma[M]$ is discrete. If $R$ is a ring such that the class of cosingular $R$-modules is closed under factor modules, then it is proved that $R$ is a $CD$-ring if and only if every cosingular $R$-module is semisimple. The relations of $CD$-rings are investigated with $V$-rings, $GV$-rings, $SC$-rings, and rings with all cosingular $R$-modules projective. If $R$ is a semilocal ring, then it is shown that $R$ is right $CD$ if and only if $R$ is left $SC$ with $Soc(_{R}R)$ essential in $_{R}R$. Also, being a $V$-ring and being a $CD$-ring coincide for local rings. Besides of these, we characterize $CD$-modules with finite hollow dimension.

Keywords

CD-module, CD-ring, cosingular module, discrete module, V -ring, semilocal module, finite hollow dimension

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