English

On the minimum size of maximal $k$-wise intersecting families

Combinatorics 2026-07-20 v1

Abstract

A family F\mathcal{F} of subsets of [n]:={1,2,,n}[n] := \{1,2,\ldots, n\} is called maximal kk-wise intersecting if every collection of at most kk members of F\mathcal{F} has a non-empty intersection, and adding any other set to F\mathcal{F} breaks this property. An old question by Erd\H{o}s and Kleitman from 1974 asks for the minimum size of a maximal kk-wise intersecting family. The case k=3k = 3 is known for all sufficiently large nn, but the problem remains open for all k4k \geqslant 4. The previous best-known upper bound is by Janzer, which has a leading term (k1)2k32n/(k1)(k-1)2^{k-3}2^{n/(k-1)} for sufficiently large nn divisible by k1k-1. In this note, we improve this bound to (4k10)2n/(k1)(4k-10)2^{n/(k-1)}, which reduces the dependence on kk in the leading coefficient from exponential to linear and is within a factor of 44 of the known lower bound.

Keywords

Cite

@article{arxiv.2607.18206,
  title  = {On the minimum size of maximal $k$-wise intersecting families},
  author = {Haoran Luo},
  journal= {arXiv preprint arXiv:2607.18206},
  year   = {2026}
}

Comments

8 pages, 1 figure. Comments are welcome