2 papers
math.RA2013
A classification of disjoint unions of two or three copies of the free monogenic semigroup
N. Abu-Ghazalh, J. D. Mitchell, Y. Péresse +1
We prove that, up to isomorphism and anti-isomorphism, there are only two semigroups which are the union of two copies of the free monogenic semigroup. Similarly, there are only ni…
math.GR2012
On disjoint unions of finitely many copies of the free monogenic semigroup
N. Abu-Ghazalh, Nik Ruskuc
Every semigroup which is a finite disjoint union of copies of the free monogenic semigroup (natural numbers under addition) is finitely presented and residually finite.