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Subdirect products of E-inversive semigroups. (English) Zbl 0691.20050
Author’s abstract: “A semigroup S is called E-inversive if for every \(a\in S\) there is an \(x\in S\) such that \((ax)^ 2=ax\). A construction of all E-inversive subdirect products of two E-inversive semigroups is given using the concept of subhomomorphism introduced by McAlister and Reilly for inversive semigroups. As an application, E-unitary covers for an E-inversive semigroup are found, in particular for those whose maximum group homomorphic image is a given group. For this purpose, the explicit form of the least group congruence on an arbitrary E-inversive semigroup is given. The special case of full subdirect products of a semilattice and a group (that is, containing all idempotents of the direct product) is investigated and, following an idea of Petrich, a construction of all these semigroups is provided. Finally, all periodic semigroups which are subdirect products of a semilattice or a band with a group are characterized.”
Reviewer: B.Pondělíček

20M10 General structure theory for semigroups