Ample groupoids that are neither almost finite nor purely infinite

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Authors: Xiaolei Wu, Mengfei Zhao, Xin Ma
Cited by: 0

Abstract

We investigate a question posed by Matui concerning the existence of minimal ample groupoids that are neither almost finite nor purely infinite, along with several natural variations of this problem. We begin by noting that there exists minimal, effective, ample transformation groupoids with this property. Moreover, such examples can be chosen to be either principal or amenable. We then construct new examples of essentially principal ample groupoids that are likewise neither almost finite nor purely infinite. These examples rely on the recent twisted topological groupoid construction of Palmer and Wu. In particular, our examples do not arise from transformation groupoids.

Fields of Study & Subjects

Homotopy and Cohomology in Algebraic Topology Advanced Algebra and Logic Advanced Operator Algebra Research

Publication details

Journal / source
Journal of Topology and Analysis
Publisher
World Scientific Pub Co Pte Ltd
Pages
1–23
Publication date
10 April 2026
Language
EN