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arXiv · 1502.02881

On the minimum degree of minimal Ramsey graphs for multiple colours

Jacob Fox·Andrey Grinshpun·Anita Liebenau·Yury Person·Tibor Szabo
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Abstract

A graph G is r-Ramsey for a graph H, denoted by G\rightarrow (H)_r, if every r-colouring of the edges of G contains a monochromatic copy of H. The graph G is called r-Ramsey-minimal for H if it is r-Ramsey for H but no proper subgraph of G possesses this property. Let s_r(H) denote the smallest minimum degree of G over all graphs G that are r-Ramsey-minimal for H. The study of the parameter s_2 was initiated by Burr, Erdős, and Lovász in 1976 when they showed that for the clique s_2(K_k)=(k-1)^2. In this paper, we study the dependency of s_r(K_k) on r and show that, under the condition that k is constant, s_r(K_k) = r^2 polylog r. We also give an upper bound on s_r(K_k) which is polynomial in both r and k, and we determine s_r(K_3) up to a factor of log r.

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Jacob Fox, Andrey Grinshpun, Anita Liebenau, Yury Person, Tibor Szabo. 2015-02-10. On the minimum degree of minimal Ramsey graphs for multiple colours. https://arxiv.org/abs/1502.02881

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