English

Colorful Helly via induced matchings

Combinatorics 2025-01-30 v2

Abstract

We establish a theorem regarding the maximum size of an {\it{induced}} matching in the bipartite complement of the incidence graph of a set system (X,F)(X,\mathcal{F}). We show that this quantity plus one provides an upper bound on the colorful Helly number of this set system, i.e. the minimum positive integer NN for which the following statement holds: if finite subfamilies F1,,FNF\mathcal{F}_1,\ldots, \mathcal{F}_{N} \subset \mathcal{F} are such that FFiF=0\cap_{F \in \mathcal{F}_{i}} F = 0 for every i=1,,Ni=1,\ldots,N, then there exists FiFiF_i \in \mathcal{F}_i such that F1FN=F_1 \cap \ldots \cap F_{N} = \emptyset. We will also discuss some natural refinements of this result and applications.

Keywords

Cite

@article{arxiv.2501.17149,
  title  = {Colorful Helly via induced matchings},
  author = {Cosmin Pohoata and Kevin Yang and Shengtong Zhang},
  journal= {arXiv preprint arXiv:2501.17149},
  year   = {2025}
}

Comments

12 pages, 2 figures. Fix issue with a figure not displaying, and correct some typos

R2 v1 2026-06-28T21:22:33.274Z