Let R be a ring (not necessarily commutative). A left R-module is said to be cotorsion if Ext 1
R (G, M)= 0 for any flat R-module G. It is well known that each pure-injective left R-module is …

Let R be a ring. A right R-module C is called a cotorsion module if Ext1R (F, C)= 0 for any flat
right R-module F. In this paper, we first characterize those rings satisfying the condition that …

Let R be a ring. A right R-module C is called cotorsion if for any flat right R-module biF. In
this paper, we first give some results on cotorsion envelopes that are analogous to those on …

Let R be a ring. A right R-module M is called f-projective if Ext1 (M, N)= 0 for any f-injective
right R-module N. We prove that (F-proj, F-inj) is a complete cotorsion theory, where F-proj …

Let I be an ideal of a commutative Noetherian ring R. It is shown that the R-modules Tor i R
(N, M) are I-cofinite for all i≥ 0 if M and N are I-cofinite R-modules and N is of dimension at …

Let $ R $ be a commutative ring, and let $ S $ be a multiplicative subset of $ R $. In this
paper, we investigate the notion of $ S $-cotorsion modules. An $ R $-module $ C $ is called …

In this paper, we introduce the notion of cofinitely injective modules and study their
properties over special types of rings. We define a right R‐module M to be cofinitely injective …

Let R be a Noetherian ring and I an ideal of R. Let M be an I-cofinite and N a finitely
generated R-module. It is shown that the R-modules $ Tor_ {i}^{R}(N, M) $ are I-cofinite for …

Let R be any ring. We prove that every right R-module is coretractable if and only if R is right
perfect and every right R-module is small coretractable if and only if all torsion theories on R …

Let I be an ideal of a commutative Noetherian ring R such that the R-modules HI i (U) are I-
cofinite, for all finitely generated R-modules U and all i∈ ℕ 0. Also, assume that the category …