A classification of disjoint unions of two or three copies of the free monogenic semigroup

2013/12/19 by N. Abu-Ghazalh, James D. Mitchell, Abu-Ghazalh, N. +5
Computer Science · Decision Sciences · Mathematics · #FOS: Mathematics #Fuzzy and Soft Set Theory #Geometric and Algebraic Topology #Group Theory (math.GR) #Rings and Algebras (math.RA) #semigroups and automata theory

paper · doi:10.48550/arxiv.1312.5518

openalex publication_date 2013/12/19 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28

Abstract

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 nine semigroups which are the union of three copies of the free monogenic semigroup. We provide finite presentations for each of these semigroups.

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