On combination theorems and Bowditch boundaries of relatively hyperbolic TDLC groups

Fuente: arXiv
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Main Authors: Datta, Swarnali, Mandal, Arunava, Tomar, Ravi
Format: Preprint
Published: 2025
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author Datta, Swarnali
Mandal, Arunava
Tomar, Ravi
author_facet Datta, Swarnali
Mandal, Arunava
Tomar, Ravi
contents Based on the work of Farb, Bowditch, and Groves-Manning on discrete relatively hyperbolic groups, we introduce an approach to relative hyperbolicity for totally disconnected locally compact (TDLC) groups. For compactly generated TDLC groups, we prove that this notion is equivalent to the one introduced by Arora-Pedroza. Let $G=A\ast_C B$ or $G=A\ast_C$ where $A$ and $B$ are relatively hyperbolic TDLC groups and $C$ is compact. We prove that $G$ is a relatively hyperbolic TDLC group and give a construction of the Bowditch boundary of $G$. As a consequence, we prove that if the rough ends of $G$ are infinite, then the topology of the Bowditch boundary of $G$ is uniquely determined by the topology of the Bowditch boundary of $A$ and $B$. Further, we show that if a relatively hyperbolic TDLC group has one rough end, then its Bowditch boundary is connected. Finally, we show that if the Gromov boundary of a hyperbolic TDLC group $G$ is totally disconnected, then $G$ splits as a finite graph of compact groups.
format Preprint
id arxiv_https___arxiv_org_abs_2508_13038
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle On combination theorems and Bowditch boundaries of relatively hyperbolic TDLC groups
Datta, Swarnali
Mandal, Arunava
Tomar, Ravi
Group Theory
Primary 20F65, 20F67, Secondary 22D05
Based on the work of Farb, Bowditch, and Groves-Manning on discrete relatively hyperbolic groups, we introduce an approach to relative hyperbolicity for totally disconnected locally compact (TDLC) groups. For compactly generated TDLC groups, we prove that this notion is equivalent to the one introduced by Arora-Pedroza. Let $G=A\ast_C B$ or $G=A\ast_C$ where $A$ and $B$ are relatively hyperbolic TDLC groups and $C$ is compact. We prove that $G$ is a relatively hyperbolic TDLC group and give a construction of the Bowditch boundary of $G$. As a consequence, we prove that if the rough ends of $G$ are infinite, then the topology of the Bowditch boundary of $G$ is uniquely determined by the topology of the Bowditch boundary of $A$ and $B$. Further, we show that if a relatively hyperbolic TDLC group has one rough end, then its Bowditch boundary is connected. Finally, we show that if the Gromov boundary of a hyperbolic TDLC group $G$ is totally disconnected, then $G$ splits as a finite graph of compact groups.
title On combination theorems and Bowditch boundaries of relatively hyperbolic TDLC groups
topic Group Theory
Primary 20F65, 20F67, Secondary 22D05
url https://arxiv.org/abs/2508.13038