English

Deforming cubulations of hyperbolic groups

Geometric Topology 2026-03-25 v2 Group Theory

Abstract

We describe a procedure to deform cubulations of hyperbolic groups by "bending hyperplanes". Our construction is inspired by related constructions like Thurston's Mickey Mouse example, walls in fibred hyperbolic 33-manifolds and free-by-Z\mathbb Z groups, and Hsu-Wise turns. As an application, we show that every cocompactly cubulated Gromov-hyperbolic group admits a proper, cocompact, essential action on a CAT(0){\rm CAT}(0) cube complex with a single orbit of hyperplanes. This answers (in the negative) a question of Wise, who proved the result in the case of free groups. We also study those cubulations of a general group GG that are not susceptible to trivial deformations. We name these "bald cubulations" and observe that every cocompactly cubulated group admits at least one bald cubulation. We then apply the hyperplane-bending construction to prove that every cocompactly cubulated hyperbolic group GG admits infinitely many bald cubulations, provided GG is not a virtually free group with Out(G){\rm Out}(G) finite. By contrast, we show that the Burger-Mozes examples each admit a unique bald cubulation.

Keywords

Cite

@article{arxiv.1912.10999,
  title  = {Deforming cubulations of hyperbolic groups},
  author = {Elia Fioravanti and Mark Hagen},
  journal= {arXiv preprint arXiv:1912.10999},
  year   = {2026}
}

Comments

44 pages, 4 figures; to appear on Journal of Topology

R2 v1 2026-06-23T12:54:56.615Z