Topologically free non-Hausdorff groupoids

Fuente: arXiv
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Auteurs principaux: Clark, Lisa Orloff, Thompson, Ryan, Tolich, Ilija
Format: Preprint
Publié: 2026
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author Clark, Lisa Orloff
Thompson, Ryan
Tolich, Ilija
author_facet Clark, Lisa Orloff
Thompson, Ryan
Tolich, Ilija
contents We study three conditions that control the behaviour of isotropy in étale groupoids, and their relationships under the additional assumptions of second-countability and Hausdorffness. We examine a number of examples that show these properties are distinct. Working under the assumption of the Zermelo-Fraenkel axioms, excluding choice, we then examine an alternate characterization of topological freeness, first introduced by Anantharaman-Delaroche, in the non-Hausdorff setting. Finally, we prove an equivalence between the Baire Category Theorem and an étale groupoid theorem, along with similar equivalences to other weakenings of the Axiom of Choice.
format Preprint
id arxiv_https___arxiv_org_abs_2602_02926
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Topologically free non-Hausdorff groupoids
Clark, Lisa Orloff
Thompson, Ryan
Tolich, Ilija
Operator Algebras
Logic
We study three conditions that control the behaviour of isotropy in étale groupoids, and their relationships under the additional assumptions of second-countability and Hausdorffness. We examine a number of examples that show these properties are distinct. Working under the assumption of the Zermelo-Fraenkel axioms, excluding choice, we then examine an alternate characterization of topological freeness, first introduced by Anantharaman-Delaroche, in the non-Hausdorff setting. Finally, we prove an equivalence between the Baire Category Theorem and an étale groupoid theorem, along with similar equivalences to other weakenings of the Axiom of Choice.
title Topologically free non-Hausdorff groupoids
topic Operator Algebras
Logic
url https://arxiv.org/abs/2602.02926