In this paper, we investigate the notions of X⊥‐projective, X‐injective, and X‐flat modules
and give some characterizations of these modules, where X is a class of left modules. We …

RINGS OVER WHICH FLAT COVERS OF SIMPLE MODULES ARE PROJECTIVE Page 1
Journal of Algebra and Its Applications Vol. 11, No. 3 (2012) 1250046 (7 pages) c© World …

Let R be a ring, na fixed nonnegative integer and F n the class of all left R-modules of flat
dimension at most n. A left R-module M is called n-copure projective if Ext R 1 (M, F)= 0 for …

In Bican et al., it is proved that all modules over an arbitrary ring have flat covers. In this
article, we shall study rings over which flat covers of finitely generated modules are …

We prove the following results for a ring R.(a) If C is a class of right R-modules closed under
direct summands and isomorphisms, then every right R-module has an epic C-envelope if …

Keskin and Harmanci defined the family B (M, X)= ${A {\leq} M|{\exists} Y {\leq} X,{\exists} f
{\in} Hom_R (M, X/Y),\; Ker\; f/A {\ll} M/A} $. And Orhan and Keskin generalized projective …

Let R be a ring, X a class of left R‐modules, S the class of submodules of X, and Q the class
of quotient‐modules of X. It is shown that SQ is precovering (preenveloping) if and only if …

We first prove that if a monomorphism is a phantom envelope of a left R-module, then its
cokernel is pure-projective; if R is a left coherent ring and an epimorphism is an Ext Ext …

Let M be a module. A\delta-cover of M is an epimorphism from a module F onto M with
a\delta-small kernel. A\delta-cover is said to be a flat\delta-cover in case F is a flat module. In …

Abstract A left R-module M is said to be fp-injective if, for every monomorphism K→ L with K
and L finitely presented left R-modules, Hom (L, M)→ Hom (K, M) is an epimorphism. A right …