One-ended spanning subforests and treeability of groups

Clinton T. Conley , Damien Gaboriau (1) , Andrew S. Marks , Robin D. Tucker-Drob

1 UMPA-ENSL - Unité de Mathématiques Pures et Appliquées

We show that several new classes of groups are measure strongly treeable. In particular, finitely generated groups admitting planar Cayley graphs, elementarily free groups, and Isom(H 2) and all its closed subgroups. In higher dimensions, we also prove a dichotomy that the fundamental group of a closed aspherical 3-manifold is either amenable or has strong ergodic dimension 2. Our main technical tool is a method for finding measurable treeings of Borel planar graphs by constructing one-ended spanning subforests in their planar dual. Our techniques for constructing one-ended spanning subforests also give a complete classification of the locally finite p.m.p. graphs which admit Borel a.e. one-ended spanning subforests.

Mots clés: 37A20 (03E15; 22F10; 05C10) ergodic and Borel equivalence relations; probability measure preserving and Borel actions of groups; locally compact groups; trees; treeability; planar graphs; elementarily free groups; cost of groups; ergodic dimension; measure equivalence

Domaines: Théorie des groupes [math.GR]; Systèmes dynamiques [math.DS]; Logique [math.LO]; Algèbres d'opérateurs [math.OA]; Probabilités [math.PR]

Clinton T. Conley, Damien Gaboriau, Andrew S. Marks, Robin D. Tucker-Drob. One-ended spanning subforests and treeability of groups. 2021. ⟨hal-03199360⟩