A threshold for relative hyperbolicity in random right-angled Coxeter groups

Fuente: arXiv
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Autores principales: Behrstock, Jason, Ciceksiz, Recep Altar, Falgas-Ravry, Victor
Formato: Preprint
Publicado: 2024
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author Behrstock, Jason
Ciceksiz, Recep Altar
Falgas-Ravry, Victor
author_facet Behrstock, Jason
Ciceksiz, Recep Altar
Falgas-Ravry, Victor
contents We consider the random right-angled Coxeter group $W_Γ$ whose presentation graph $Γ\sim \mathcal{G}_{n,p}$ is an Erd{\H o}s--Rényi random graph on $n$ vertices with edge probability $p=p(n)$. We establish that $p=1/\sqrt{n}$ is a threshold for relative hyperbolicity of the random group $W_Γ$. As a key step in the proof, we determine the minimal number of pairs of generators that must commute in a right-angled Coxeter group which is not relatively hyperbolic, a result which is of independent interest. We also show that there is an interval of edge probabilities of width $Ω(1/\sqrt{n})$ in which the random right-angled Coxeter group has precisely cubic divergence. This interval is between the thresholds for relative hyperbolicity (whence exponential divergence) and quadratic divergence. Moreover, a simple random walk on any Cayley graph of the random right-angled Coxeter group for $p$ in this interval satisfies a central limit theorem.
format Preprint
id arxiv_https___arxiv_org_abs_2407_12959
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle A threshold for relative hyperbolicity in random right-angled Coxeter groups
Behrstock, Jason
Ciceksiz, Recep Altar
Falgas-Ravry, Victor
Group Theory
Combinatorics
Geometric Topology
Probability
05C80 20F55 20F67 20F65
We consider the random right-angled Coxeter group $W_Γ$ whose presentation graph $Γ\sim \mathcal{G}_{n,p}$ is an Erd{\H o}s--Rényi random graph on $n$ vertices with edge probability $p=p(n)$. We establish that $p=1/\sqrt{n}$ is a threshold for relative hyperbolicity of the random group $W_Γ$. As a key step in the proof, we determine the minimal number of pairs of generators that must commute in a right-angled Coxeter group which is not relatively hyperbolic, a result which is of independent interest. We also show that there is an interval of edge probabilities of width $Ω(1/\sqrt{n})$ in which the random right-angled Coxeter group has precisely cubic divergence. This interval is between the thresholds for relative hyperbolicity (whence exponential divergence) and quadratic divergence. Moreover, a simple random walk on any Cayley graph of the random right-angled Coxeter group for $p$ in this interval satisfies a central limit theorem.
title A threshold for relative hyperbolicity in random right-angled Coxeter groups
topic Group Theory
Combinatorics
Geometric Topology
Probability
05C80 20F55 20F67 20F65
url https://arxiv.org/abs/2407.12959