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

Abu-Ghazalh, N., Mitchell, J. D., Péresse, Y. and Ruškuc, N. (2015) A classification of disjoint unions of two or three copies of the free monogenic semigroup. Semigroup Forum, 91 (1). pp. 53-61. ISSN 0037-1912

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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.

Item Type	Article
Additional information	This is the accepted manuscript version of the following article: N. Abu-Ghazalh, J. D. Mitchell, Y. Péresse, and N. Ruškuc, “A classification of disjoint unions of two or three copies of the free monogenic semigroup”, Semigroup Forum, Vol. 91(1): 53-61, December 2014. The final published version is available at: https://link.springer.com/article/10.1007/s00233-014-9638-4 © Springer Science+Business Media New York 2014
Keywords	semigroups, abstract algebra
Date Deposited	15 May 2025 13:11
Last Modified	31 May 2025 00:05