Non-arithmeticity of length spectra of subgroups of mapping class groups

Fuente: arXiv
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Autori principali: Choi, Inhyeok, Kim, Dongryul M.
Natura: Preprint
Pubblicazione: 2026
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author Choi, Inhyeok
Kim, Dongryul M.
author_facet Choi, Inhyeok
Kim, Dongryul M.
contents In this paper, we prove that every non-elementary subgroup of the mapping class group of a surface has non-arithmetic Teichmüller length spectrum. Namely, Teichmüller translation lengths of its pseudo-Anosov elements generate a dense additive subgroup of $\mathbb{R}$. We prove this by introducing the notion of cross-ratios on $\mathcal{MF}$ and $\mathcal{PMF}$, and studying its geometric and dynamical properties, despite the lack of negatively curved features of the Teichmüller space nor the conformal geometry on $\mathcal{PMF}$.
format Preprint
id arxiv_https___arxiv_org_abs_2605_13064
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Non-arithmeticity of length spectra of subgroups of mapping class groups
Choi, Inhyeok
Kim, Dongryul M.
Geometric Topology
Dynamical Systems
Group Theory
In this paper, we prove that every non-elementary subgroup of the mapping class group of a surface has non-arithmetic Teichmüller length spectrum. Namely, Teichmüller translation lengths of its pseudo-Anosov elements generate a dense additive subgroup of $\mathbb{R}$. We prove this by introducing the notion of cross-ratios on $\mathcal{MF}$ and $\mathcal{PMF}$, and studying its geometric and dynamical properties, despite the lack of negatively curved features of the Teichmüller space nor the conformal geometry on $\mathcal{PMF}$.
title Non-arithmeticity of length spectra of subgroups of mapping class groups
topic Geometric Topology
Dynamical Systems
Group Theory
url https://arxiv.org/abs/2605.13064