English

A realisation result for moduli spaces of group actions on the line

Group Theory 2024-09-04 v4 Dynamical Systems

Abstract

Given a finitely generated group GG, the possible actions of GG on the real line (without global fixed points), considered up to semi-conjugacy, can be encoded by the space of orbits of a flow on a compact space (Y,Φ)(Y, \Phi) naturally associated with GG and uniquely defined up to flow equivalence, that we call the \emph{Deroin space} of GG. We show a realisation result: every expansive flow (Y,Φ)(Y, \Phi) on a compact metrisable space of topological dimension 1, satisfying some mild additional assumptions, arises as the Deroin space of a finitely generated group. This is proven by identifying the Deroin space of an explicit family of groups acting on suspension flows of subshifts, which is a variant of a construction introduced by the second and fourth authors. This result provides a source of examples of finitely generated groups satisfying various new phenomena for actions on the line, related to their rigidity/flexibility properties and to the structure of (path-)connected components of the space of actions.

Keywords

Cite

@article{arxiv.2306.03846,
  title  = {A realisation result for moduli spaces of group actions on the line},
  author = {Joaquín Brum and Nicolás Matte Bon and Cristóbal Rivas and Michele Triestino},
  journal= {arXiv preprint arXiv:2306.03846},
  year   = {2024}
}

Comments

32 pages; v4: minor corrections and references updated, final version to appear in the Journal of Topology