Non-trivial $d$-wise Intersecting families
Abstract
For an integer , a family of sets is \textit{d-wise intersecting} if for any distinct sets , , and if . Hilton and Milner conjectured that for and large enough , the extremal non-trivial -wise intersecting family of -element subsets of is one of the following two families: \begin{align*} &\mathcal{H}(k,d) = \{A \in \binom{[n]}{k} : [d-1] \subset A, A \cap [d,k+1] \neq \emptyset\} \cup \{[k+1] \setminus \{i \} : i \in [d - 1]\} \\ &\mathcal{A}(k,d) = \{ A \in \binom{[n]}{k} : |A \cap [d+1]| \geq d \}. \end{align*} The celebrated Hilton-Milner Theorem states that is the unique extremal non-trivial intersecting family for . We prove the conjecture and prove a stability theorem, stating that any large enough non-trivial -wise intersecting family of -element subsets of is a subfamily of or .
Keywords
Cite
@article{arxiv.1911.01031,
title = {Non-trivial $d$-wise Intersecting families},
author = {Jason O'Neill and Jacques Verstraete},
journal= {arXiv preprint arXiv:1911.01031},
year = {2019}
}