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arXiv · 2409.05487

Intersections of iterated shadows

Hou Tin Chau·David Ellis·Marius Tiba
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Abstract

We show that if $\mathcal{A} \subset {[n] \choose n/2}$ with measure bounded away from zero and from one, then the $Ω(\sqrt{n})$-iterated upper shadows of $\mathcal{A}$ and $\mathcal{A}^c$ intersect in a set of positive measure. This confirms (in a strong form) a conjecture of Friedgut. It can be seen as a stability result for the Kruskal--Katona theorem.

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Hou Tin Chau, David Ellis, Marius Tiba. 2024-09-13. Intersections of iterated shadows. https://arxiv.org/abs/2409.05487

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