Hyperfiniteness for group actions on trees

Srivatsav Kunnawalkam Elayavalli, Koichi Oyakawa, Forte Shinko, Pieter Spaas

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Abstract

We identify natural conditions for a countable group acting on a countable tree which imply that the orbit equivalence relation of the induced action on the Gromov boundary is Borel hyperfinite. Examples of this condition include acylindrical actions. We also identify a natural weakening of the aforementioned conditions that implies measure hyperfiniteness of the boundary action. We then document examples of group actions on trees whose boundary action is not hyperfinite.
Original languageEnglish
JournalProceedings of the American Mathematical Society
Volume152
Issue number9
Pages (from-to)3657-3664
ISSN0002-9939
DOIs
Publication statusPublished - 2024

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