Additive quasi-isometries and cacti

Abstract

We prove that if a geodesic metric space contains no $c$-fat theta curve for some $c>0$, then it is $(1,K)$-quasi-isometric to a cactus graph, where $K$ depends only on $c$. Using a coarse characterization of cacti in terms of $c$-fat theta curves this implies that every geodesic metric space quasi-isometric to a cactus is $(1,K)$-quasi-isometric to a cactus graph.

15 pages