Counting mapping classes by Nielsen-Thurston type

Fuente: arXiv
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Auteurs principaux: Dowdall, Spencer, Masur, Howard
Format: Preprint
Publié: 2023
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author Dowdall, Spencer
Masur, Howard
author_facet Dowdall, Spencer
Masur, Howard
contents This paper concerns the lattice counting problem for the mapping class group of a surface $S$ acting on Teichmüller space with the Teichmüller metric. In that problem the goal is to count the number of mapping classes that send a given point $x$ into the ball of radius $R$ centered about another point $y$. For the action of the entire group, Athreya, Bufetov, Eskin and Mirzakhani have shown this quantity is asymptotic to $e^{hR}$, where $h$ is the dimension of the Teichmüller space. We refine the problem by considering the action various distinguished subsets of elements and counting these separately. For the set of finite-order elements, we show the associated count grows coarsely at the rate of $e^{hR/2}$, that is, with half the exponent. For the reducible elements, the associated count grows coarsely at the rate of $e^{(h-1)R}$. Finally, for the set of all multitwists, the coarse growth rate is also $e^{hR/2}$. To obtain these quantitative estimates, we introduce a new notion in Teichmüller geometry, called complexity length, which reflects some aspects of the negative curvature of curve complexes and also has applications to counting problems.
format Preprint
id arxiv_https___arxiv_org_abs_2305_03721
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle Counting mapping classes by Nielsen-Thurston type
Dowdall, Spencer
Masur, Howard
Geometric Topology
Dynamical Systems
This paper concerns the lattice counting problem for the mapping class group of a surface $S$ acting on Teichmüller space with the Teichmüller metric. In that problem the goal is to count the number of mapping classes that send a given point $x$ into the ball of radius $R$ centered about another point $y$. For the action of the entire group, Athreya, Bufetov, Eskin and Mirzakhani have shown this quantity is asymptotic to $e^{hR}$, where $h$ is the dimension of the Teichmüller space. We refine the problem by considering the action various distinguished subsets of elements and counting these separately. For the set of finite-order elements, we show the associated count grows coarsely at the rate of $e^{hR/2}$, that is, with half the exponent. For the reducible elements, the associated count grows coarsely at the rate of $e^{(h-1)R}$. Finally, for the set of all multitwists, the coarse growth rate is also $e^{hR/2}$. To obtain these quantitative estimates, we introduce a new notion in Teichmüller geometry, called complexity length, which reflects some aspects of the negative curvature of curve complexes and also has applications to counting problems.
title Counting mapping classes by Nielsen-Thurston type
topic Geometric Topology
Dynamical Systems
url https://arxiv.org/abs/2305.03721