Axioms for unary semigroups via division operations

TL;DR

This paper extends the characterization of groups via division operations to broader classes of unary semigroups, providing new axioms and solving an open problem in the field.

Contribution

It introduces axioms for unary semigroups based on division operations and characterizes various classes, including inverse and Clifford semigroups, extending known results.

Findings

Characterizations of unary semigroups via division operations

Axioms for classes like inverse and Clifford semigroups

Resolution of an open problem in unary semigroup theory

Abstract

When a semigroup has a unary operation, it is possible to define two binary operations, namely, left and right division. In addition it is well known that groups can be defined in terms of those two divisions. The aim of this paper is to extend those results to other classes of unary semigroups. In the first part of the paper we provide characterizations for several classes of unary semigroups, including (a special class of) E-inversive, regular, completely regular, inverse, Clifford, etc., in terms of left and right division. In the second part we solve a problem that was posed elsewhere. The paper closes with a list of open problems.