On the maximum number of distinct intersections in an intersecting family (2108.00479v1)

Abstract: For $n > 2k \geq 4$ we consider intersecting families $\mathcal F$ consisting of $k$-subsets of ${1, 2, \ldots, n}$. Let $\mathcal I(\mathcal F)$ denote the family of all distinct intersections $F \cap F'$, $F \neq F'$ and $F, F'\in \mathcal F$. Let $\mathcal A$ consist of the $k$-sets $A$ satisfying $|A \cap {1, 2, 3}| \geq 2$. We prove that for $n \geq 50 k^2$ $|\mathcal I(\mathcal F)|$ is maximized by $\mathcal A$.