English

Intersecting families with covering number $3$

Combinatorics 2025-11-26 v3 Discrete Mathematics

Abstract

A covering number of a family is the size of the smallest set that intersects all sets from the family. In 1978 Frankl determined for nn0(k)n\ge n_0(k) the largest intersecting family of kk-element subsets of [n][n] with covering number 33. In this paper, we essentially settle this problem, showing that the same family is extremal for any k100k\ge 100 and n>2kn>2k.

Keywords

Cite

@article{arxiv.2405.02621,
  title  = {Intersecting families with covering number $3$},
  author = {Andrey Kupavskii},
  journal= {arXiv preprint arXiv:2405.02621},
  year   = {2025}
}

Comments

arXiv admin note: substantial text overlap with arXiv:1810.00920

R2 v1 2026-06-28T16:16:33.764Z