Treewidth, crushing, and hyperbolic volume

Abstract

We prove that there exists a universal constant \(c\) such that any closed hyperbolic 3-manifold admits a triangulation of treewidth at most \(c\) times its volume. The converse is not true: we show there exists a sequence of hyperbolic 3-manifolds of bounded treewidth but volume approaching infinity. Along the way, we prove that crushing a normal surface in a triangulation does not increase the carving-width, and hence crushing any number of normal surfaces in a triangulation affects treewidth by at most a constant multiple.