A characterization of Gromov hyperbolicity via quasigeodesic subspaces

TL;DR

This paper characterizes Gromov hyperbolic spaces by examining the union properties of quasigeodesic subspaces, extending known results from geodesic subspaces and providing a new perspective on hyperbolicity.

Contribution

It introduces a novel characterization of Gromov hyperbolic spaces using quasigeodesic subspaces, generalizing previous geodesic-based criteria.

Findings

Characterization of Gromov hyperbolic spaces via quasigeodesic subspaces

Extension of union properties from geodesic to quasigeodesic subspaces

Provides a new framework for understanding hyperbolicity

Abstract

By a geodesic subspace of a metric space $X$ we mean a subset $A$ of $X$ such that any two points in $A$ can be connected by a geodesic in $A$. It is easy to check that a geodesic metric space $X$ is an $\mathbb{R}$-tree (that is, a $0$-hyperbolic space in the sense of Gromov) if and only if the union of any two intersecting geodesic subspaces is again a geodesic subspace. In this paper, we prove an analogous characterization of general Gromov hyperbolic spaces, where we replace geodesic subspaces by quasigeodesic subspaces.