English

On the number of pairwise touching cylinders in $\mathbb{R}^d$

Combinatorics 2026-01-01 v1

Abstract

John E. Littlewood posted the question {\em ``Is it possible in 3-space for seven infinite circular cylinders of unit radius each to touch all the others? Seven is the number suggested by counting constants.''} Boz\'oki, Lee, and R\'onyai constructed a configuration of 7 mutually touching unit cylinders. The best-known upper bounds show that at most 10 unit cylinders in R3\mathbb{R}^3 can mutually touch. We consider this problem in higher dimensions, and obtain exponential (in dd) upper bounds on the number of mutually touching cylinders in Rd\mathbb{R}^d. Our method is fairly flexible, and it makes use of the fact that cylinder touching can be expressed as a combination of polynomial equalities and non-equalities.

Keywords

Cite

@article{arxiv.2512.24595,
  title  = {On the number of pairwise touching cylinders in $\mathbb{R}^d$},
  author = {Jozsef Solymosi and Josh Zahl},
  journal= {arXiv preprint arXiv:2512.24595},
  year   = {2026}
}