Hierarchically hyperbolic groups are determined by their Morse boundaries

TL;DR

This paper extends the classification of hyperbolic groups by their Morse boundaries to a broader class of hierarchically hyperbolic spaces, establishing a quasi-isometry criterion based on boundary homeomorphisms.

Contribution

It generalizes a known boundary classification result from hyperbolic groups to hierarchically hyperbolic spaces with cocompact actions, including new cases like mapping class groups.

Findings

Quasi-isometry of spaces characterized by boundary homeomorphisms.

Extension of boundary classification to hierarchically hyperbolic spaces.

Applicable to groups like mapping class groups and 3-manifold groups.

Abstract

We generalize a result of Paulin on the Gromov boundary of hyperbolic groups to the Morse boundary of proper, maximal hierarchically hyperbolic spaces admitting cocompact group actions by isometries. Namely we show that if the Morse boundaries of two such spaces each contain at least three points, then the spaces are quasi-isometric if and only if there exists a 2-stable, quasi-m\"obius homeomorphism between their Morse boundaries. Our result extends a recent result of Charney-Murray, who prove such a classification for CAT(0) groups, and is new for mapping class groups and the fundamental groups of $3$-manifolds without Nil or Sol components.