English

$s$-almost $t$-intersecting families for finite sets

Combinatorics 2026-01-13 v4

Abstract

A family F\mathcal{F} of kk-subsets of an nn-set is called ss-almost tt-intersecting if each member is tt-disjoint with at most ss members. In this paper, we prove that, if F\left|\mathcal{F}\right| is maximum, then F\mathcal{F} consists of all kk-subsets containing a fixed tt-subset. Consequently, it is natural to consider the maximum-sized F\mathcal{F} with FFF<t\left|\bigcap_{F\in\mathcal{F}} F\right|<t. The famous Hilton-Milner theorem settles the case where F\mathcal{F} is tt-intersecting. We characterize the remaining case completely.

Keywords

Cite

@article{arxiv.2410.20185,
  title  = {$s$-almost $t$-intersecting families for finite sets},
  author = {Dehai Liu and Kaishun Wang and Tian Yao},
  journal= {arXiv preprint arXiv:2410.20185},
  year   = {2026}
}
R2 v1 2026-06-28T19:36:40.230Z