We establish equivalent conditions under which every object in an Abelian category has a
monic X-cover and an epic X-envelope respectively, when X is a class of objects closed …

T -扩张代数的Tate上同调 Page 1 山东大学学报(理学版)2021年1月第56卷第1期 E-mail:xblxb@sdu.edu.cn
Journal of Shandong University (Natural Science)ꎬ Vol.56ꎬ No.1ꎬ 2021 http:/ / lxbwk.njournal.sdu.edu.cn …

设R 是环ꎬmꎬn 是非负整数ꎬ 称右R-模C 是(mꎬn)-余挠模ꎬ 是指对任何平坦维数不超过n
的右R-模Nꎬ 都有Extm+ 1 R (Nꎬ C)= 0ꎮ 称右R-模M 为(mꎬn)-平坦模ꎬ 是指对任何(mꎬn) …

Let $ R $ be a ring, and $ n $ a fixed nonnegative integer. An $ R $-module $ W $ is called $
L_ {n} $-injective if ${\rm Ext} _ {R}^{1}(M, W)= 0$ for any $ R $-module $ M $ with flat …

Let R be a ring, and let (F, C) be a cotorsion theory. In this article, the notion of F-perfect
rings is introduced as a nontrial generalization of perfect rings and A-perfect rings. A ring R …

Let (𝒜, ℬ) be a hereditary cotorsion pair in Mod R. We show that the induced cotorsion pair
is complete if and only if the induced cotorsion pair is complete. As applications, some …