RINGS CHARACTERIZED BY COFLAT MODULES

In this paper, some new characterizations of semihereditary ring, regular ring, pp ring and IF ring with FP injective modules, coflat modules and coherent rings are given: 1) R is pp ring if and only if the homomorphic imagine of p injective module is p injective module; 2) R is semihereditary ring if and only if the sum of two coflat submodules of every R module is coflat module; 3) R is right IF ring if and only if R is left coherent ring and left coflat ring; 4) R is regular ring if and only if R is right IF ring, right pp ring and RM * is flat module for each right p injective module M .