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math.OA2026
Topologically free non-Hausdorff groupoids
Lisa Orloff Clark, Ryan Thompson, Ilija Tolich
We study three conditions that control the behaviour of isotropy in étale groupoids, and their relationships under the additional assumptions of second-countability and Hausdorffne…
math.OA2026
A dichotomy for inverse-semigroup crossed products via dynamical Cuntz semigroups
Becky Armstrong, Lisa Orloff Clark, Astrid an Huef +2
We characterise stable finiteness and pure infiniteness of the essential crossed product of a C*-algebra by an action of an inverse semigroup. Under additional assumptions, we prov…
math.OA2017
HNN extensions of quasi-lattice ordered groups and their operator algebras
Astrid an Huef, Iain Raeburn, Ilija Tolich
The Baumslag-Solitar group is an example of an HNN extension. Spielberg showed that it has a natural positive cone, and that it is then a quasi-lattice ordered group in the sense o…