Contramodules over pro-perfect topological rings
Abstract
For four wide classes of topological rings , we show that all flat left -contramodules have projective covers if and only if all flat left -contramodules are projective if and only if all left -contramodules have projective covers if and only if all descending chains of cyclic discrete right -modules terminate if and only if all the discrete quotient rings of are left perfect. Three classes of topological rings for which this holds are the complete, separated topological associative rings with a base of neighborhoods of zero formed by open two-sided ideals such that either the ring is commutative, or it has a countable base of neighborhoods of zero, or it has only a finite number of semisimple discrete quotient rings. The fourth class consists of all the topological rings with a base of neighborhoods of zero formed by open right ideals which have a closed two-sided ideal with certain properties such that the quotient ring is a topological product of rings from the previous three classes. The key technique on which the proofs are based is the contramodule Nakayama lemma for topologically T-nilpotent ideals.
Cite
@article{arxiv.1807.10671,
title = {Contramodules over pro-perfect topological rings},
author = {Leonid Positselski},
journal= {arXiv preprint arXiv:1807.10671},
year = {2022}
}
Comments
LaTeX 2e with xy-pic, 53 pages, 3 commutative diagrams; v2: this is an improved version of Sections 1-10 of v1, the rest of v1 was moved to arXiv:1907.04973 and arXiv:1907.05537; v.5: Sections 1.8, 1.9, 1.10, and 1.11 expanded; v.6: small additions and corrections, references updated, the numbering of sections (and of subsections in the introduction) shifted to agree with the journal version