Combinatorial Theory

A family \(\mathcal{F}\) of subsets of \(\{1,\dots,n\}\) is called \(k\)-wise intersecting if any \(k\) members of \(\mathcal{F}\) have non-empty intersection, and it is called maximal \(k\)-wise intersecting if no family strictly containing \(\mathcal{F}\) satisfies this condition. We show that for each \(k\geq 2\) there is a maximal \(k\)-wise intersecting family of size \(O(2^{n/(k-1)})\). Up to a constant factor, this matches the best known lower bound, and answers an old question of Erdős and Kleitman, recently studied by Hendrey, Lund, Tompkins, and Tran.

Mathematics Subject Classifications: 05D05

Keywords: Intersecting family, saturation, set system