English

Geometric structures related to the braided Thompson groups

Group Theory 2021-04-13 v2 Geometric Topology

Abstract

In previous work, joint with Bux, Fluch, Marschler and Witzel, we proved that the braided Thompson groups are of type F\textrm{F}_\infty. The proof utilized certain contractible cube complexes, which in this paper we prove are CAT(0). We then use this fact to compute the geometric invariants Σm(Fbr)\Sigma^m(F_{\textrm{br}}) of the pure braided Thompson group FbrF_{\textrm{br}}. Only the first invariant Σ1(Fbr)\Sigma^1(F_{\textrm{br}}) was previously known. A consequence of our computation is that as soon as a subgroup of FbrF_{\textrm{br}} containing the commutator subgroup [Fbr,Fbr][F_{\textrm{br}},F_{\textrm{br}}] is finitely presented, it is automatically of type F\textrm{F}_\infty.

Keywords

Cite

@article{arxiv.1803.02717,
  title  = {Geometric structures related to the braided Thompson groups},
  author = {Matthew C. B. Zaremsky},
  journal= {arXiv preprint arXiv:1803.02717},
  year   = {2021}
}

Comments

22 pages, 3 figures. v2: Removed Subsection 4.3, after a mistake came to light. This subsection was unrelated to the rest of the paper, so nothing else changed in any important ways

R2 v1 2026-06-23T00:45:18.248Z