Cross-free families have linear size

Fuente: arXiv
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Autore principale: Tomon, István
Natura: Preprint
Pubblicazione: 2026
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author Tomon, István
author_facet Tomon, István
contents Two subsets $A$ and $B$ of a ground set $X$ are \emph{crossing} if none of the four sets $A\setminus B,B\setminus A,A\cap B, X\setminus (A\cup B)$ are empty. Almost fifty years ago, Karzanov and Lomonosov conjectured that every family of subsets of an $n$-element ground set with no $k$-pairwise crossing members has size $O(kn)$. We prove the bound $O_k(n)$, settling (arguably) the main problem about the growth rate of such families.
format Preprint
id arxiv_https___arxiv_org_abs_2603_05443
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Cross-free families have linear size
Tomon, István
Combinatorics
Two subsets $A$ and $B$ of a ground set $X$ are \emph{crossing} if none of the four sets $A\setminus B,B\setminus A,A\cap B, X\setminus (A\cup B)$ are empty. Almost fifty years ago, Karzanov and Lomonosov conjectured that every family of subsets of an $n$-element ground set with no $k$-pairwise crossing members has size $O(kn)$. We prove the bound $O_k(n)$, settling (arguably) the main problem about the growth rate of such families.
title Cross-free families have linear size
topic Combinatorics
url https://arxiv.org/abs/2603.05443