English

Embedding groups into boundedly acyclic groups

Group Theory 2025-04-15 v4 K-Theory and Homology

Abstract

We show that the \s{\phi}-labeled Thompson groups and the twisted Brin--Thompson groups are boundedly acyclic. This allows us to prove several new embedding results for groups. First, every group of type FnF_n embeds quasi-isometrically into a boundedly acyclic group of type FnF_n that has no proper finite index subgroups. This improves a result of Bridson and a theorem of Fournier-Facio--L\"oh--Moraschini. Second, every group of type FnF_n embeds quasi-isometrically into a 55-uniformly perfect group of type FnF_n. Third, using Belk--Zaremsky's construction of twisted Brin--Thompson groups, we show that every finitely generated group embeds quasi-isometrically into a finitely generated boundedly acyclic simple group. We also partially answer some questions of Brothier and Tanushevski regarding the finiteness property of ϕ\phi-labeled Thompson group Vϕ(G)V_\phi(G) and Fϕ(G)F_\phi(G).

Keywords

Cite

@article{arxiv.2407.07703,
  title  = {Embedding groups into boundedly acyclic groups},
  author = {Fan Wu and Xiaolei Wu and Mengfei Zhao and Zixiang Zhou},
  journal= {arXiv preprint arXiv:2407.07703},
  year   = {2025}
}

Comments

Added a new section about l2-invisibility, some other small changes. 42pages. Final version, to appear in J. Lond. Math. Soc

R2 v1 2026-06-28T17:35:48.387Z