English

On vertex Ramsey graphs with forbidden subgraphs

Combinatorics 2023-11-10 v2

Abstract

A classical vertex Ramsey result due to Ne\v{s}et\v{r}il and R\"odl states that given a finite family of graphs F\mathcal{F}, a graph AA and a positive integer rr, if every graph BFB\in\mathcal{F} has a 22-vertex-connected subgraph which is not a subgraph of AA, then there exists an F\mathcal{F}-free graph which is vertex rr-Ramsey with respect to AA. We prove that this sufficient condition for the existence of an F\mathcal{F}-free graph which is vertex rr-Ramsey with respect to AA is also necessary for large enough number of colours rr. We further show a generalisation of the result to a family of graphs and the typical existence of such a subgraph in a dense binomial random graph.

Keywords

Cite

@article{arxiv.2211.13966,
  title  = {On vertex Ramsey graphs with forbidden subgraphs},
  author = {Sahar Diskin and Ilay Hoshen and Michael Krivelevich and Maksim Zhukovskii},
  journal= {arXiv preprint arXiv:2211.13966},
  year   = {2023}
}

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R2 v1 2026-06-28T07:12:25.602Z