English

A note on strongly and totally chain intersecting families

Combinatorics 2023-02-14 v1

Abstract

Bern\'ath and Gerbner in 2007 introduced (p,q)(p,q)-chain intersecting families of subsets of an nn-element underlying set. Those have the property that for any pp-chain A1A2ApA_1\subsetneq A_2\subsetneq \dots \subsetneq A_p and qq-chain B1B2BqB_1\subsetneq B_2\subsetneq \dots \subsetneq B_q, we have ApBqA_p\cap B_q\neq \emptyset. Bern\'ath and Gerbner determined the largest cardinality of such families. They also introduced strongly (p,q)(p,q)-chain intersecting families, where ApB1A_p\cap B_1\neq \emptyset and totally (p,q)(p,q)-chain intersecting families, where A1B1A_1\cap B_1\neq \emptyset. They obtained some partial results on the maximum cardinality of such families. We extend those results by determining the largest cardinality of strongly (p,q)(p,q)-chain intersecting families if nn is sufficiently large, and by determining the largest cardinality of totally (2,2)(2,2)-chain intersecting families.

Keywords

Cite

@article{arxiv.2302.05514,
  title  = {A note on strongly and totally chain intersecting families},
  author = {Dániel Gerbner},
  journal= {arXiv preprint arXiv:2302.05514},
  year   = {2023}
}
R2 v1 2026-06-28T08:37:27.173Z