Equidivisibility and profinite coproduct

Abstract

The aim of this work is to investigate the behavior of equidivisibility under coproduct in the category of pro-V semigroups, where V is a pseudovariety of nite semigroups. Exploring the relationship with the two-sided Karnofsky{Rhodes expansion, the notions of KR-cover and strong KR-cover for pro nite semigroups are introduced. The former is stronger than equidivisibility and the latter provides a characterization of equidivisible pro nite semigroups with an extra mild condi- tion, so-called letter super-cancellativity. Furthermore, under the assumption that V is closed under two-sided Karnofsky{Rhodes expansion, closure of some classes of equidivisible pro-V semigroups under ( nite) V-coproduct is established.