Gromov-Hausdorff distances between quotient metric spaces

Fuente: arXiv
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Main Authors: Adams, Henry, Albornoz, Armando, Bruda, Glenn, Du, Jianda, van Rensburg, Lodewyk Jansen, Leon, Alejandro, Narayanan, Saketh, Panish, Connor, Rugenstein, Chris, Wall, Martin
Format: Preprint
Published: 2024
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author Adams, Henry
Albornoz, Armando
Bruda, Glenn
Du, Jianda
van Rensburg, Lodewyk Jansen
Leon, Alejandro
Narayanan, Saketh
Panish, Connor
Rugenstein, Chris
Wall, Martin
author_facet Adams, Henry
Albornoz, Armando
Bruda, Glenn
Du, Jianda
van Rensburg, Lodewyk Jansen
Leon, Alejandro
Narayanan, Saketh
Panish, Connor
Rugenstein, Chris
Wall, Martin
contents The Hausdorff distance measures how far apart two sets are in a common metric space. By contrast, the Gromov-Hausdorff distance provides a notion of distance between two abstract metric spaces. How do these distances behave for quotients of spaces under group actions? Suppose a group $G$ acts by isometries on two metric spaces $X$ and $Y$. In this article, we study how the Hausdorff and Gromov-Hausdorff distances between $X$ and $Y$ and their quotient spaces $X/G$ and $Y/G$ are related. For the Hausdorff distance, we show that if $X$ and $Y$ are $G$-invariant subsets of a common metric space, then we have $d_{\mathrm{H}}(X,Y)=d_{\mathrm{H}}(X/G,Y/G)$. However, the Gromov-Hausdorff distance does not preserve this relationship: we show how to make the ratio $\frac{d_{\mathrm{GH}}(X/G,Y/G)}{d_{\mathrm{GH}}(X,Y)}$ both arbitrarily large and arbitrarily small, even if $X$ is an arbitrarily dense $G$-invariant subset of $Y$.
format Preprint
id arxiv_https___arxiv_org_abs_2410_14938
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Gromov-Hausdorff distances between quotient metric spaces
Adams, Henry
Albornoz, Armando
Bruda, Glenn
Du, Jianda
van Rensburg, Lodewyk Jansen
Leon, Alejandro
Narayanan, Saketh
Panish, Connor
Rugenstein, Chris
Wall, Martin
Metric Geometry
The Hausdorff distance measures how far apart two sets are in a common metric space. By contrast, the Gromov-Hausdorff distance provides a notion of distance between two abstract metric spaces. How do these distances behave for quotients of spaces under group actions? Suppose a group $G$ acts by isometries on two metric spaces $X$ and $Y$. In this article, we study how the Hausdorff and Gromov-Hausdorff distances between $X$ and $Y$ and their quotient spaces $X/G$ and $Y/G$ are related. For the Hausdorff distance, we show that if $X$ and $Y$ are $G$-invariant subsets of a common metric space, then we have $d_{\mathrm{H}}(X,Y)=d_{\mathrm{H}}(X/G,Y/G)$. However, the Gromov-Hausdorff distance does not preserve this relationship: we show how to make the ratio $\frac{d_{\mathrm{GH}}(X/G,Y/G)}{d_{\mathrm{GH}}(X,Y)}$ both arbitrarily large and arbitrarily small, even if $X$ is an arbitrarily dense $G$-invariant subset of $Y$.
title Gromov-Hausdorff distances between quotient metric spaces
topic Metric Geometry
url https://arxiv.org/abs/2410.14938