Idempotent-Aided Factorizations of Regular Elements of a Semigroup

Abstract

In the present paper, we introduce the concept of idempotent-aided factorization (I.-A. factorization) of a regular element of a semigroup, which can be understood as a semigroup-theoretical extension of full-rank factorization of matrices over a field. I.-A. factorization of a regular element d is defined by means of an idempotent e from its Green’s D-class as decomposition into the product d=uv, so that the element u belongs to the Green’s R-class of the element d and the Green’s L-class of the idempotent e, while the element v belongs to the Green’s L-class of the element d and the Green’s R-class of the idempotent e. The main result of the paper is a theorem which states that each regular element of a semigroup possesses an I.-A. factorization with respect to each idempotent from its Green’s D-class. In addition, we prove that when one of the factors is given, then the other factor is uniquely determined. I.-A. factorizations are then used to provide new existence conditions and characterizations of group inverses and (b,c)-inverses in a semigroup. In our further research, these factorizations will be applied to matrices with entries in a field, and efficient algorithms for realization of such factorizations will be provided.

Keywords

• Green’s equivalences
• trace product
• factorization
• group inverse
• (<i>b</i>,<i>c</i>)-inverse