English

A group with Property (T) acting on the circle

Group Theory 2023-08-25 v3 Dynamical Systems

Abstract

We exhibit a topological group GG with property (T) acting non-elementarily and continuously on the circle. This group is an uncountable totally disconnected closed subgroup of Homeo+(S1)\operatorname{Homeo}^+(\mathbf{S}^1). It has a large unitary dual since it separates points. It comes from homeomorphisms of dendrites and a kaleidoscopic construction. Alternatively, it can be seen as the group of elements preserving some specific geodesic lamination of the hyperbolic disk. We also prove that this action is unique up to conjugation and that it can't be smoothened in any way. Finally, we determine the universal minimal flow of the group GG.

Keywords

Cite

@article{arxiv.2011.12861,
  title  = {A group with Property (T) acting on the circle},
  author = {Bruno Duchesne},
  journal= {arXiv preprint arXiv:2011.12861},
  year   = {2023}
}

Comments

A mistake has been corrected in the proof of Theorem 1.14. I thank Gianluca Basso for the correction

R2 v1 2026-06-23T20:30:34.311Z