English

Excluding hooks and their complements

Combinatorics 2015-08-06 v2

Abstract

The celebrated Erdos-Hajnal conjecture states that for every nn-vertex undirected graph HH there exists \eps(H)>0\eps(H)>0 such that every graph GG that does not contain HH as an induced subgraph contains a clique or an independent set of size at least n\eps(H)n^{\eps(H)}. A weaker version of the conjecture states that the polynomial-size clique/independent set phenomenon occurs if one excludes both HH and its complement H\complH^{\compl}. We show that the weaker conjecture holds if HH is any path with a pendant edge at its third vertex; thus we give a new infinite family of graphs for which the conjecture holds.

Keywords

Cite

@article{arxiv.1508.00634,
  title  = {Excluding hooks and their complements},
  author = {Krzysztof Choromanski and Dvir Falik and Anita Liebenau and Viresh Patel and Marcin Pilipczuk},
  journal= {arXiv preprint arXiv:1508.00634},
  year   = {2015}
}
R2 v1 2026-06-22T10:25:38.255Z