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Vietnam Journal of Mathematics 33:2 (2005) 214-221
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When $M$-Cosingular Modules Are Projective
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Derya Keskin T\" ut\" unc\" u and Rachid Tribak
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Abstract.
Let $M$ be an $R$-module. Talebi and Vanaja investigate
the category $\sigma[M]$ such that every $M$-cosingular module in $\sigma[M]$ is
projective in $\sigma[M]$. In the light of this property
we call $M$ a COSP-module if every $M$-cosingular module is
projective in $\sigma[M]$. This note
is devoted to the investigation of these classes of modules. We prove
that every COSP-module is a coatomic module having a semisimple radical.
We also characterise COSP-module when every injective module in $\sigma[M]$ is
amply supplemented. Finally we obtain that a COSP-module is artinian if
and only if every submodule has finite hollow dimension.
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