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arXiv · 2201.02375

Not all nilpotent monoids are finitely related

Markus Steindl
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Abstract

A finite semigroup is finitely related (has finite degree) if its term functions are determined by a finite set of finitary relations. For example, it is known that all nilpotent semigroups are finitely related. A nilpotent monoid is a nilpotent semigroup with adjoined identity. We show that every $4$-nilpotent monoid is finitely related. We also give an example of a $5$-nilpotent monoid that is not finitely related. To our knowledge, this is the first example of a finitely related semigroup where adjoining an identity yields a semigroup which is not finitely related. We also provide examples of finitely related semigroups which have subsemigroups, homomorphic images, and in particular Rees quotients, that are not finitely related.

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Markus Steindl. 2022-01-07. Not all nilpotent monoids are finitely related. https://arxiv.org/abs/2201.02375

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