Equivalence of definitions of AF groupoid

We prove the equivalence of two definitions of AF groupoid in the literature: one by Renault and the other by Farsi, Kumjian, Pask and Sims. In both definitions, an AF groupoid is an increasing union of more basic groupoids, called elementary groupoids. Surprisingly, the two definitions of elementary groupoid are not equivalent; they coincide if and only if the local homeomorphism that characterises them is a covering map.

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Journal
Proceedings of the American Mathematical Society
Published
2025-01-29
DOI
https://doi.org/10.1090/proc/16932
Primary Topic
Advanced Operator Algebra Research
Type
article
Field-Weighted Citation Impact
0.00

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article

Equivalence of definitions of AF groupoid

Lisa Clark, Camila F. Sehnem, Astrid an Huef, R. Teixeira De Lima
Proceedings of the American Mathematical Society
Advanced Operator Algebra Research
article

Equivalence of definitions of AF groupoid

Lisa Clark, Camila F. Sehnem, Astrid an Huef, R. Teixeira De Lima
article en

Abstract

We prove the equivalence of two definitions of AF groupoid in the literature: one by Renault and the other by Farsi, Kumjian, Pask and Sims. In both definitions, an AF groupoid is an increasing union of more basic groupoids, called elementary groupoids. Surprisingly, the two definitions of elementary groupoid are not equivalent; they coincide if and only if the local homeomorphism that characterises them is a covering map.

Proceedings of the American Mathematical SocietyVol. 153(3)
University of Waterloo (CA), Victoria University of Wellington (NZ)
Marsden Fund
Openalex Percentile: Top 96%
Advanced Operator Algebra Research
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Equivalence of definitions of AF groupoid — Lisa Clark, Camila F. Sehnem, et al. · Proceedings of the American Mathematical Society (2025) | TGRS Research Map | TGRS