English

Holes with hats and Erd\H{o}s-Hajnal

Combinatorics 2020-06-16 v2

Abstract

A "hole-with-hat" in a graph GG is an induced subgraph of GG that consists of a cycle of length at least four, together with one further vertex that has exactly two neighbours in the cycle, adjacent to each other, and the "house" is the smallest, on five vertices. It is not known whether there exists ϵ>0\epsilon>0 such that every graph GG containing no house has a clique or stable set of cardinality at least Gϵ|G|^\epsilon; this is one of the three smallest open cases of the Erd\H{o}s-Hajnal conjecture and has been the subject of much study. We prove that there exists ϵ>0\epsilon>0 such that every graph GG with no hole-with-hat has a clique or stable set of cardinality at least Gϵ|G|^\epsilon

Keywords

Cite

@article{arxiv.2005.02896,
  title  = {Holes with hats and Erd\H{o}s-Hajnal},
  author = {Maria Chudnovsky and Paul Seymour},
  journal= {arXiv preprint arXiv:2005.02896},
  year   = {2020}
}