English

Central extensions of associative algebras and weakly action representable categories

Category Theory 2022-07-05 v3 Rings and Algebras

Abstract

A central extension is a regular epimorphism in a Barr exact category C\mathscr{C} satisfying suitable conditions involving a given Birkhoff subcategory of C\mathscr{C} (joint work with G. M. Kelly, 1994). In this paper we take C\mathscr{C} to be the category of (not-necessarily-unital) algebras over a (unital) commutative ring and consider central extensions with respect to the category of commutative algebras. We propose a new approach that avoids the intermediate notion of central extension due to A. Fr\"ohlich in showing that α:AB\alpha:A\to B is a central extension if and only if aa=aaaa'=a'a for all a,aAa,a'\in A with α(a)=0\alpha(a')=0. This approach motivates introducing what we call weakly action representable categories\textit{weakly action representable categories}, and we show that such categories are always action accessible. We also make remarks on what we call initial weak representations of actions\textit{initial weak representations of actions} and formulate several open questions.

Keywords

Cite

@article{arxiv.2206.02744,
  title  = {Central extensions of associative algebras and weakly action representable categories},
  author = {George Janelidze},
  journal= {arXiv preprint arXiv:2206.02744},
  year   = {2022}
}