Quasi-isometric rigidity for lamplighters with lamps of polynomial growth
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arXiv
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2025
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| author | Dumoncel, Vincent |
| author_facet | Dumoncel, Vincent |
| contents | A quasi-isometry between two connected graphs is measure-scaling if one can control precisely the sizes of pre-images of finite subsets. Such a notion is motivated by the work of Eskin-Fisher-Whyte on lamplighters over $\mathbb{Z}$ and the work of Dymarz on biLipschitz equivalences of amenable groups, and led Genevois and Tessera to introduce the scaling group $\text{Sc}(X)$ of an amenable bounded degree graph $X$. The main result of our article is a rigidity property for quasi-isometries between lamplighters with lamps of polynomial growth. Under assumptions on $G$ and $H$, any such quasi-isometry $N\wr G\longrightarrow M\wr H$ must be measure-scaling for some scaling factor depending on the growth degrees of $N$ and $M$. In particular, the scaling group of such wreath products is reduced to $\lbrace 1\rbrace$. As applications, we obtain additional examples of pairs of quasi-isometric groups that are not biLipschitz equivalent. We also give applications to the quasi-isometric classification of some iterated wreath products, and we exhibit the first example of an amenable finitely generated group $H$ which is lamplighter-rigid, in the sense that $\mathbb{Z}/n\mathbb{Z}\wr H$ and $\mathbb{Z}/m\mathbb{Z}\wr H$ are quasi-isometric if and only if $n=m$. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2502_01849 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Quasi-isometric rigidity for lamplighters with lamps of polynomial growth Dumoncel, Vincent Group Theory 20F65, 20F69 A quasi-isometry between two connected graphs is measure-scaling if one can control precisely the sizes of pre-images of finite subsets. Such a notion is motivated by the work of Eskin-Fisher-Whyte on lamplighters over $\mathbb{Z}$ and the work of Dymarz on biLipschitz equivalences of amenable groups, and led Genevois and Tessera to introduce the scaling group $\text{Sc}(X)$ of an amenable bounded degree graph $X$. The main result of our article is a rigidity property for quasi-isometries between lamplighters with lamps of polynomial growth. Under assumptions on $G$ and $H$, any such quasi-isometry $N\wr G\longrightarrow M\wr H$ must be measure-scaling for some scaling factor depending on the growth degrees of $N$ and $M$. In particular, the scaling group of such wreath products is reduced to $\lbrace 1\rbrace$. As applications, we obtain additional examples of pairs of quasi-isometric groups that are not biLipschitz equivalent. We also give applications to the quasi-isometric classification of some iterated wreath products, and we exhibit the first example of an amenable finitely generated group $H$ which is lamplighter-rigid, in the sense that $\mathbb{Z}/n\mathbb{Z}\wr H$ and $\mathbb{Z}/m\mathbb{Z}\wr H$ are quasi-isometric if and only if $n=m$. |
| title | Quasi-isometric rigidity for lamplighters with lamps of polynomial growth |
| topic | Group Theory 20F65, 20F69 |
| url | https://arxiv.org/abs/2502.01849 |