English

Piercing intersecting convex sets

Combinatorics 2025-02-12 v2

Abstract

Assume two finite families A\mathcal A and B\mathcal B of convex sets in R3\mathbb{R}^3 have the property that ABA\cap B\ne \emptyset for every AAA \in \mathcal A and BBB\in \mathcal B. Is there a constant γ>0\gamma >0 (independent of A\mathcal A and B\mathcal B) such that there is a line intersecting γA\gamma|\mathcal A| sets in A\mathcal A or γB\gamma|\mathcal B| sets in B\mathcal B? This is an intriguing Helly-type question from a paper by Mart\'{i}nez, Roldan and Rubin. We confirm this in the special case when all sets in A\mathcal A lie in parallel planes and all sets in B\mathcal B lie in parallel planes; in fact, all sets from one of the two families has a line transversal.

Keywords

Cite

@article{arxiv.2409.06472,
  title  = {Piercing intersecting convex sets},
  author = {Imre Bárány and Travis Dillon and Dömötör Pálvölgyi and Dániel Varga},
  journal= {arXiv preprint arXiv:2409.06472},
  year   = {2025}
}

Comments

Accepted to Linear Algebra and its Applications