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arXiv · 2404.14005

Translational hulls of semigroups of endomorphisms of an algebra

Victoria Gould·Ambroise Grau·Marianne Johnson·Mark Kambites
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Abstract

We consider the translational hull $\Omega(I)$ of an arbitrary subsemigroup $I$ of an endomorphism monoid $\mathrm{End}(A)$ where $A$ is a universal algebra. We give conditions for every bi-translation of $I$ to be realised by transformations, or by endomorphisms, of $A$. We demonstrate that certain of these conditions are also sufficient to provide natural isomorphisms between the translational hull of $I$ and the idealiser of $I$ within $\mathrm{End}(A)$, which in the case where $I$ is an ideal is simply $\mathrm{End}(A)$. We describe the connection between these conditions and work of Petrich and Gluskin in the context of densely embedded ideals. Where the conditions fail, we develop a methodology to extract information concerning $\Omega(I)$ from the translational hull $\Omega(I/{\approx})$ of a quotient $I/{\approx}$ of $I$. We illustrate these concepts in detail in the cases where $A$ is: a free algebra; an independence algebra; a finite symmetric group.

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Victoria Gould, Ambroise Grau, Marianne Johnson, Mark Kambites. 2024-04-22. Translational hulls of semigroups of endomorphisms of an algebra. https://arxiv.org/abs/2404.14005

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