$\mathbb{R}$--trees and accessibility over arc-stabilisers

Abstract

Let $G\curvearrowright T$ be a minimal action on an $\mathbb{R}$--tree with $G$ finitely presented. Assuming that $G$ is accessible over the family of arc-stabilisers of $T$, we give a description of the point-stabilisers of $T$ in terms of simplicial trees. In particular, these point-stabilisers are finitely generated. This has applications to the study of automorphisms of right-angled Artin groups and special groups.

18 pages; previously an appendix to arXiv:2501.12321; to appear in Groups, Geometry & Dynamics