International Journal of Mathematics and Mathematical Sciences
Volume 2005 (2005), Issue 18, Pages 2945-2975
Idempotent-separating extensions of regular semigroups
Department of Mathematics, Kongu Engineering College, Perundurai 638052, Tamil Nadu, India
Received 1 July 2004; Revised 10 March 2005
Copyright © 2005 A. Tamilarasi. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
For a regular biordered set , the notion of -diagram and the associated regular semigroup was introduced in our previous paper (1995). Given a regular biordered set , an -diagram in a category is a collection of objects, indexed by the elements of and morphisms of satisfying certain compatibility conditions. With such an -diagram we associate a regular semigroup having as its biordered set of idempotents. This regular semigroup is analogous to automorphism group of a group. This paper provides an application of to the idempotent-separating extensions of regular semigroups. We introduced the concept of crossed pair and used it to describe all extensions of a regular semigroup S by a group -diagram . In this paper, the necessary and sufficient condition for the existence of an extension of by is provided. Also we study cohomology and obstruction theories and find a relationship with extension theory for regular semigroups.