English

Strengthening Rodl's theorem

Combinatorics 2022-08-04 v2

Abstract

What can be said about the structure of graphs that do not contain an induced copy of some graph H? Rodl showed in the 1980s that every H-free graph has large parts that are very dense or very sparse. More precisely, let us say that a graph F on n vertices is c-restricted if either F or its complement has maximum degree at most cn. Rodl proved that for every graph H, and every c>0, every H-free graph G has a linear-sized set of vertices inducing a c-restricted graph. We strengthen Rodl's result as follows: for every graph H, and all c>0, every H-free graph can be partitioned into a bounded number of subsets inducing c-restricted graphs.

Keywords

Cite

@article{arxiv.2105.07370,
  title  = {Strengthening Rodl's theorem},
  author = {Maria Chudnovsky and Alex Scott and Paul Seymour and Sophie Spirkl},
  journal= {arXiv preprint arXiv:2105.07370},
  year   = {2022}
}
R2 v1 2026-06-24T02:09:03.132Z