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arXiv · 2508.17516

The action of an inverse semigroup on its Stone-\v{C}ech compactification

Joseph P. Z. Gondek·Charles Starling
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Abstract

We initiate the study of the Stone-\v{C}ech transformation groupoid $\mathcal{G} = \mathcal{S}\ltimes\beta\mathcal{S}$ of an inverse semigroup $\mathcal{S}$. We prove that the properties of being Hausdorff, principal, and effective are all equivalent for $\mathcal{G}$, and give an algebraic condition on $\mathcal{S}$ equivalent to the Hausdorffness of $\mathcal{G}$. We show that the Hausdorffness of Exel's tight groupoid $\mathcal{G}_{\text{tight}}(\mathcal{S})$ is necessary for the Hausdorffness of $\mathcal{G}$. Finally, we clarify the connection between several crossed product constructions involving this groupoid, and show that when it is Hausdorff and $\mathcal{S}$ has the Property (FL) of Lled\'o and Mart\'inez, then $\mathcal{G}$ is amenable if and only if the reduced C$^*$-algebra $\text{C}^*_r(\mathcal{S})$ is exact.

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Joseph P. Z. Gondek, Charles Starling. 2025-08-24. The action of an inverse semigroup on its Stone-\v{C}ech compactification. https://arxiv.org/abs/2508.17516

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