English

1-Uryson width and covers

Metric Geometry 2025-08-19 v2 Differential Geometry

Abstract

We investigate the following question: Do there exist Riemannian polyhedra XX such that the 1-Uryson width of their universal covers UW1(X~)\mathrm{UW}_1(\widetilde{X}) is bounded but UW1(X)\mathrm{UW}_1(X) is arbitrarily large? We rule out two specific cases: when π1(X)\pi_1(X) is virtually cyclic and when XX is a Riemannian surface. More specifically, we show that if XX is a compact polyhedron with a virtually cyclic fundamental group, then its 1-Uryson width is bounded by the 1-Uryson width of its universal cover X~\widetilde{X}. Precisely: UW1(X)6UW1(X~).\mathrm{UW}_1(X) \leq 6 \cdot \mathrm{UW}_1(\widetilde{X}). We show that if XX is a Riemannian surface with boundary then UW1(X)UW1(X~).\mathrm{UW}_1(X) \leq \mathrm{UW}_1(\widetilde{X}). Furthermore, we show that if there exist spaces XX for which UW1(X~)\mathrm{UW}_1(\widetilde{X}) is bounded while UW1(X)\mathrm{UW}_1(X) is arbitrarily large, then such examples must already appear in low dimensions. In particular, such XX can be found among Riemannian 22-complexes.

Cite

@article{arxiv.2505.21126,
  title  = {1-Uryson width and covers},
  author = {Hannah Alpert and Arka Banerjee and Panos Papasoglu},
  journal= {arXiv preprint arXiv:2505.21126},
  year   = {2025}
}

Comments

25 pages, 4 figures. Corrects part of Remark 2.3 and extends Theorem B to all compact surfaces with Riemannian metrics

R2 v1 2026-07-01T02:42:49.185Z