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چکیده
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Let R be a ring and M be an R-module. In this paper we investigate modules M such that every (simple) cosingular R-module is M-projective. We prove that every simple cosingular module is M-projective if and only if for N ≤ T ≤ M, whenever T/N is simple cosingular, then N is a direct summand of T. We show that every simple cosingular right R-module is projective if and only if R is a right GV-ring. It is also shown that for a right perfect ring R, every cosingular right R-module is projective if and only if R is a right GV-ring. In addition, we prove that if every δ-cosingular right R-module is semisimple, then Z(M) is a direct summand of M for every right R-module M if and only if Zδ(M) is a direct summand of M for every right R-module M.
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