English

Irreducible Sp-representations and subgroup distortion in the mapping class group

Geometric Topology 2020-06-11 v4 Group Theory

Abstract

We prove that various subgroups of the mapping class group Mod(Σ)Mod(\Sigma) of a surface Σ\Sigma are at least exponentially distorted. Examples include the Torelli group (answering a question of Hamenstadt), the "point-pushing" and surface braid subgroups, and the Lagrangian subgroup. Our techniques include a method to compute lower bounds on distortion via representation theory and an extension of Johnson theory to arbitrary subgroups of H1(Σ;Z)H_1(\Sigma;\mathbb{Z}).

Keywords

Cite

@article{arxiv.0707.2262,
  title  = {Irreducible Sp-representations and subgroup distortion in the mapping class group},
  author = {Nathan Broaddus and Benson Farb and Andrew Putman},
  journal= {arXiv preprint arXiv:0707.2262},
  year   = {2020}
}

Comments

17 pages; fixed TeX errors in arXiv title and abstract, paper unchanged

R2 v1 2026-06-21T08:58:34.772Z