The Johnson-Morita theory for the handlebody group

Fuente: arXiv
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Autores principales: Habiro, Kazuo, Massuyeau, Gwenael
Formato: Preprint
Publicado: 2024
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author Habiro, Kazuo
Massuyeau, Gwenael
author_facet Habiro, Kazuo
Massuyeau, Gwenael
contents The Johnson-Morita theory is an algebraic approach to the mapping class group of a surface, in which one considers its action on the successive nilpotent quotients of the fundamental group of the surface. In this paper, we develop an analogue of this theory for the handlebody group, i.e. the mapping class group of a 3-dimensional handlebody. Thus, we obtain a filtration on the handlebody group, prove that its associated graded embeds into a Lie algebra of "special derivations", and give an explicit diagrammatic description of this graded Lie algebra in terms of "oriented trees with beads". Our new diagrammatic method reveals part of the richness of the algebraic structure of the handlebody group, which lies mainly in the subgroup generated by Dehn twists along meridians: the so-called "twist group". As an application, we obtain that each term of the associated graded of the lower central series of the twist group is infinitely generated.
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id arxiv_https___arxiv_org_abs_2401_07705
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle The Johnson-Morita theory for the handlebody group
Habiro, Kazuo
Massuyeau, Gwenael
Geometric Topology
Group Theory
The Johnson-Morita theory is an algebraic approach to the mapping class group of a surface, in which one considers its action on the successive nilpotent quotients of the fundamental group of the surface. In this paper, we develop an analogue of this theory for the handlebody group, i.e. the mapping class group of a 3-dimensional handlebody. Thus, we obtain a filtration on the handlebody group, prove that its associated graded embeds into a Lie algebra of "special derivations", and give an explicit diagrammatic description of this graded Lie algebra in terms of "oriented trees with beads". Our new diagrammatic method reveals part of the richness of the algebraic structure of the handlebody group, which lies mainly in the subgroup generated by Dehn twists along meridians: the so-called "twist group". As an application, we obtain that each term of the associated graded of the lower central series of the twist group is infinitely generated.
title The Johnson-Morita theory for the handlebody group
topic Geometric Topology
Group Theory
url https://arxiv.org/abs/2401.07705