Hyperbolic Simplices of Maximal Inradius

Fuente: arXiv
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Hauptverfasser: Duchesne, Bruno, Simon, Christopher-Lloyd
Format: Preprint
Veröffentlicht: 2025
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author Duchesne, Bruno
Simon, Christopher-Lloyd
author_facet Duchesne, Bruno
Simon, Christopher-Lloyd
contents For $n\in \mathbb{N}$, consider a hyperbolic $n$-dimensional simplex $Δ$, defined by $1+n$ points in the compactified hyperbolic space $\mathbf{H}^n \sqcup \partial \mathbf{H}^n$. For each integer $m\le n$, denote $δ^n_m(Δ)\in [0,+\infty]$ the Hausdorff distance between its skeleta of dimensions $n$ and $m$. In particular, $δ^n_{n-1}(Δ)$ is its inradius. The maximum of $δ^n_m(Δ)$ over $Δ\in (\mathbf{H}^n \sqcup \partial \mathbf{H}^n)^{1+n}$ is denoted $μ^n_m\in [0,+\infty]$. We first show that $Δ$ has maximal inradius $δ^n_{n-1}(Δ)=μ^n_m$ if and only if its is (total) ideal and regular; for which the inradius is given by $\tanh μ^n_{n-1} = 1/n$. We deduce that $Δ$ has maximal $δ^n_{n-1}(Δ)=μ^n_m$ if and only if it is (total) ideal and regular. We compute that the maximal distance to the $1$-skeleton $μ^n_1$ is given by $\left(\tanh μ^n_1\right)^2 = (n-1)/(2n)$ and deduce that those are uniformly bounded by $\lim_{n} μ^n_1 = \log(1+\sqrt{2})$.
format Preprint
id arxiv_https___arxiv_org_abs_2512_17096
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Hyperbolic Simplices of Maximal Inradius
Duchesne, Bruno
Simon, Christopher-Lloyd
Metric Geometry
52B11, 52B15, 52A40
For $n\in \mathbb{N}$, consider a hyperbolic $n$-dimensional simplex $Δ$, defined by $1+n$ points in the compactified hyperbolic space $\mathbf{H}^n \sqcup \partial \mathbf{H}^n$. For each integer $m\le n$, denote $δ^n_m(Δ)\in [0,+\infty]$ the Hausdorff distance between its skeleta of dimensions $n$ and $m$. In particular, $δ^n_{n-1}(Δ)$ is its inradius. The maximum of $δ^n_m(Δ)$ over $Δ\in (\mathbf{H}^n \sqcup \partial \mathbf{H}^n)^{1+n}$ is denoted $μ^n_m\in [0,+\infty]$. We first show that $Δ$ has maximal inradius $δ^n_{n-1}(Δ)=μ^n_m$ if and only if its is (total) ideal and regular; for which the inradius is given by $\tanh μ^n_{n-1} = 1/n$. We deduce that $Δ$ has maximal $δ^n_{n-1}(Δ)=μ^n_m$ if and only if it is (total) ideal and regular. We compute that the maximal distance to the $1$-skeleton $μ^n_1$ is given by $\left(\tanh μ^n_1\right)^2 = (n-1)/(2n)$ and deduce that those are uniformly bounded by $\lim_{n} μ^n_1 = \log(1+\sqrt{2})$.
title Hyperbolic Simplices of Maximal Inradius
topic Metric Geometry
52B11, 52B15, 52A40
url https://arxiv.org/abs/2512.17096