Abstract
The aim of this paper is to characterize $n$-Gorenstein rings in terms of Gorenstein injective modules and the Ext functor. We will show that if $R$ is a left and right noetherian ring and $n$ is a positive integer, then $R$ is $n$-Gorenstein if and only if $M$ being Gorenstein injective means that Ext$^{1}$ $(L, M )=0$ for all countably generated $R$-modules $L$ of projective dimension at most $n$. In particular, if $R$ is $n$-Gorenstein, then an $R$-module $M$ is Gorenstein injective if and only if it is $U$-Gorenstein injective whenever $U$ is a free $R$-module with a countable base.
Citation
Edgar E. Enochs. Overtoun M. G. Jenda. "Gorenstein injective modules and Ext.." Tsukuba J. Math. 28 (2) 303 - 309, December 2004. https://doi.org/10.21099/tkbjm/1496164803
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