数学
逆极限
态射
猜想
封面(代数)
阿贝尔群
纯数学
投影覆盖
直接限值
阿贝尔范畴
简单(哲学)
极限(数学)
投射试验
射影平面
维数(图论)
离散数学
拓扑(电路)
组合数学
射影空间
共渗
几何学
数学分析
工程类
哲学
相关性
认识论
机械工程
作者
Silvana Bazzoni,Leonid Positselski,Jan Šťovíček
摘要
We show that a direct limit of projective contramodules (over a right linear topological ring) is projective if it has a projective cover. A similar result is obtained for $\infty$-strictly flat contramodules of projective dimension not exceeding $1$, using an argument based on the notion of the topological Jacobson radical. Covers and precovers of direct limits of more general classes of objects, both in abelian categories with exact and with nonexact direct limits, are also discussed, with an eye towards the Enochs conjecture about covers and direct limits, using locally split (mono)morphisms as the main technique. In particular, we offer a simple elementary proof of the Enochs conjecture for the left class of an $n$-tilting cotorsion pair in an abelian category with exact direct limits.
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