PS-injective Modules, PS-flat Modules and PS-coherent Rings

摘要

A left ideal I of a ring R is small in case for every proper left ideal K of R, K + I≠R. A ring R is called left PS-coherent if every principally small left ideal Ra is finitely presented. We develop, in this paper, PS-coherent rings as a generalization of P-coherent rings and J-coherent rings. To characterize PS-coherent rings, we first introduce PS-injective and PS-flat modules, and discuss the relation between them over some spacial rings. Some properties of left PS-coherent rings are also studied.