A classification of disjoint unions of two or three copies of the free monogenic semigroup
Abstract
We prove that, up to isomorphism and antiisomorphism, there are only two semigroups which are the union of two copies of the free monogenic semigroup. Similarly, there are only nine semigroups which are the union of three copies of the free monogenic semigroup. We provide finite presentations for each of these semigroups.
 Publication:

arXiv eprints
 Pub Date:
 December 2013
 arXiv:
 arXiv:1312.5518
 Bibcode:
 2013arXiv1312.5518A
 Keywords:

 Mathematics  Rings and Algebras;
 Mathematics  Group Theory
 EPrint:
 7 pages, minor corrections suggested by the referee