Large cliques or co-cliques in hypergraphs with forbidden order-size pairs
Abstract
The well-known Erd\H{o}s-Hajnal conjecture states that for any graph , there exists such that every -vertex graph that contains no induced copy of has a homogeneous set of size at least . We consider a variant of the Erd\H{o}s-Hajnal problem for hypergraphs where we forbid a family of hypergraphs described by their orders and sizes. For graphs, we observe that if we forbid induced subgraphs on vertices and edges for any positive and , then we obtain large homogeneous sets. For triple systems, in the first nontrivial case , for every , we give bounds on the minimum size of a homogeneous set in a triple system where the number of edges spanned by every four vertices is not in . In most cases the bounds are essentially tight. We also determine, for all , whether the growth rate is polynomial or polylogarithmic. Some open problems remain.
Keywords
Cite
@article{arxiv.2305.01531,
title = {Large cliques or co-cliques in hypergraphs with forbidden order-size pairs},
author = {Maria Axenovich and Domagoj Bradač and Lior Gishboliner and Dhruv Mubayi and Lea Weber},
journal= {arXiv preprint arXiv:2305.01531},
year = {2023}
}
Comments
A preliminary version of this manuscript appeared as arXiv:2303.09578