$n$-cocoherent rings, $n$-cosemihereditary rings and $n$-v-rings
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abstract
let $r$ be a ring, and let $n, d$ be non-negative integers. a right $r$-module $m$ is called $(n, d)$-projective if $ext^{d+1}_r(m, a)=0$ for every $n$-copresented right $r$-module $a$. $r$ is called right $n$-cocoherent if every $n$-copresented right $r$-module is $(n+1)$-coprese-nted, it is called a right co-$(n,d)$-ring if every right $r$-module is $(n, d)$-projective. $r$ is called right $n$-cosemihereditary if every submodule of a projective right $r$-module is $(n, 0)$-projective, it is called a right $n$-v-ring if it is a right co-$(n,0)$-ring. some properties of $(n, d)$-projective modules and $(n, d)$-projective dimensions of modules over $n$-cocoherent rings are studied. certain characterizations of $n$-copresented modules, $(n, 0)$-projective modules, right $n$-cocoherent rings, right $n$-cosemihereditary rings, as well as right $n$-v-rings are given respectively.
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Journal title:
bulletin of the iranian mathematical societyجلد ۴۰، شماره ۴، صفحات ۸۰۹-۸۲۲
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