Local-to-global Urysohn width estimates

Abstract

The notion of the Urysohn $d$-width measures to what extent a metric space can be approximated by a $d$-dimensional simplicial complex. We investigate how local Urysohn width bounds on a riemannian manifold affect its global width. We bound the $1$-width of a Riemannian manifold in terms of its first homology and the supremal width of its unit balls. Answering a question of Larry Guth, we give examples of $n$-manifolds of considerable $(n-1)$-width in which all unit balls have arbitrarily small $1$-width. We also give examples of topologically simple manifolds that are locally nearly low-dimensional.

9 pages, 2 figures; Theorem 1.3 generalized to all dimensions

References in corpus (1)

• Linear bounds for constants in Gromov's systolic inequality and related results

Cited by in corpus (1)

• Macroscopic scalar curvature and codimension 2 width