On rings with envelopes and covers regarding to , and flat modules
Abstract
In this paper, by taking the class of all (or ) right -modules for general envelopes and covers, we characterize a semisimple artinian ring (or a right perfect ring) via -covers (or -envelopes) and a right -ring (or a right noetherian -ring) via -covers (or -envelopes). By using isosimple-projective preenvelope, we obtained that if is a semiperfect right FGF ring (or left coherent ring), then every isosimple right -module has a projective cover. Moreover, we also characterize semihereditary serial rings (respectively, hereditary artinian serial rings) in terms of epic flat (respectively, projective) envelopes.
Communicated by A. Leroy