Torsion at the Threshold for Mapping Class Groups

Fuente: arXiv
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Autores principales: Jekel, Solomon, Rolland, Rita Jiménez
Formato: Preprint
Publicado: 2024
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author Jekel, Solomon
Rolland, Rita Jiménez
author_facet Jekel, Solomon
Rolland, Rita Jiménez
contents The mapping class group $Γ_g^ 1$ of a closed orientable surface of genus $g \geq 1$ with one marked point can be identified, by the Nielsen action, with a subgroup of the group of orientation preserving homeomorphims of the circle. This inclusion pulls back the powers of the discrete universal Euler class producing classes $\text{E}^n \in H^{2n}(Γ_g^1;\mathbb{Z})$ for all $n\geq 1$. In this paper we study the power $n=g,$ and prove: $\text{E}^g$ is a torsion class which generates a cyclic subgroup of $H^{2g}(Γ_g^1;\mathbb{Z})$ whose order is a positive integer multiple of $4g(2g+1)(2g-1)$.
format Preprint
id arxiv_https___arxiv_org_abs_2409_07311
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Torsion at the Threshold for Mapping Class Groups
Jekel, Solomon
Rolland, Rita Jiménez
Geometric Topology
Algebraic Topology
The mapping class group $Γ_g^ 1$ of a closed orientable surface of genus $g \geq 1$ with one marked point can be identified, by the Nielsen action, with a subgroup of the group of orientation preserving homeomorphims of the circle. This inclusion pulls back the powers of the discrete universal Euler class producing classes $\text{E}^n \in H^{2n}(Γ_g^1;\mathbb{Z})$ for all $n\geq 1$. In this paper we study the power $n=g,$ and prove: $\text{E}^g$ is a torsion class which generates a cyclic subgroup of $H^{2g}(Γ_g^1;\mathbb{Z})$ whose order is a positive integer multiple of $4g(2g+1)(2g-1)$.
title Torsion at the Threshold for Mapping Class Groups
topic Geometric Topology
Algebraic Topology
url https://arxiv.org/abs/2409.07311