Classification of orientable torus bundles over closed orientable surfaces

Fuente: arXiv
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Main Authors: Kasuya, Naohiko, Noda, Issei
Format: Preprint
Published: 2024
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author Kasuya, Naohiko
Noda, Issei
author_facet Kasuya, Naohiko
Noda, Issei
contents Let $g$ be a non-negative integer, $Σ_g$ a closed orientable surface of genus $g$, and $\mathcal{M}_g$ its mapping class group. We classify all the group homomorphisms $π_1(Σ_g)\to G$ up to the action of $\mathcal{M}_g$ on $π_1(Σ_g)$ in the following cases; (1) $G=PSL(2;\mathbb{Z})$, (2) $G=SL(2;\mathbb{Z})$. As an application of the case (2), we completely classify orientable $T^2$-bundles over closed orientable surfaces up to bundle isomorphisms. In particular, we show that any orientable $T^2$-bundle over $Σ_g$ with $g\geq 1$ is isomorphic to the fiber connected sum of $g$ pieces of $T^2$-bundles over $T^2$. Moreover, the classification result in the case (1) can be generalized into the case where $G$ is the free product of finite number of finite cyclic groups. We also apply it to an extension problem of maps from a closed surface to the connected sum of lens spaces.
format Preprint
id arxiv_https___arxiv_org_abs_2406_14138
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Classification of orientable torus bundles over closed orientable surfaces
Kasuya, Naohiko
Noda, Issei
Geometric Topology
Algebraic Topology
Group Theory
55R15, 57R22, 20F65, 57K43
Let $g$ be a non-negative integer, $Σ_g$ a closed orientable surface of genus $g$, and $\mathcal{M}_g$ its mapping class group. We classify all the group homomorphisms $π_1(Σ_g)\to G$ up to the action of $\mathcal{M}_g$ on $π_1(Σ_g)$ in the following cases; (1) $G=PSL(2;\mathbb{Z})$, (2) $G=SL(2;\mathbb{Z})$. As an application of the case (2), we completely classify orientable $T^2$-bundles over closed orientable surfaces up to bundle isomorphisms. In particular, we show that any orientable $T^2$-bundle over $Σ_g$ with $g\geq 1$ is isomorphic to the fiber connected sum of $g$ pieces of $T^2$-bundles over $T^2$. Moreover, the classification result in the case (1) can be generalized into the case where $G$ is the free product of finite number of finite cyclic groups. We also apply it to an extension problem of maps from a closed surface to the connected sum of lens spaces.
title Classification of orientable torus bundles over closed orientable surfaces
topic Geometric Topology
Algebraic Topology
Group Theory
55R15, 57R22, 20F65, 57K43
url https://arxiv.org/abs/2406.14138