On radical square zero rings

Let \(\Lambda\) be a connected left artinian ring with radical square zero and with \(n\) simple modules. If \(\Lambda\)  is not self-injective, then we show that any module \(M\) with \(\operatorname{Ext}^i(M,\Lambda) = 0\) for \(1 \le i \le n+1\) is projective. We also determine the structure of t...

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Bibliographic Details
Date:2018
Main Authors: Ringel, Claus Michael, Xiong, Bao-Lin
Format: Article
Language:English
Published: Lugansk National Taras Shevchenko University 2018
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Online Access:https://admjournal.luguniv.edu.ua/index.php/adm/article/view/727
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Journal Title:Algebra and Discrete Mathematics

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Algebra and Discrete Mathematics
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Summary:Let \(\Lambda\) be a connected left artinian ring with radical square zero and with \(n\) simple modules. If \(\Lambda\)  is not self-injective, then we show that any module \(M\) with \(\operatorname{Ext}^i(M,\Lambda) = 0\) for \(1 \le i \le n+1\) is projective. We also determine the structure of the artin algebras with radical square zero and \(n\) simple modules which have a non-projective module \(M\) such that \(\operatorname{Ext}^i(M,\Lambda) = 0\) for \(1 \le i \le n\).