$n$-cocoherent rings‎, ‎$n$-cosemihereditary rings and $n$-V-rings

Document Type : Research Paper

Author

Department of mathematics,jiaxing university,jiaxing,zhejiang province,china,314001

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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