English

Large monochromatic components in hypergraphs with large minimum codegree

Combinatorics 2023-09-20 v2

Abstract

A result of Gy\'arf\'as says that for every 33-coloring of the edges of the complete graph KnK_n, there is a monochromatic component of order at least n2\frac{n}{2}, and this is best possible when 44 divides nn. Furthermore, for all k3k\geq 3 and every (k+1)(k+1)-coloring of the edges of the complete kk-uniform hypergraph KnkK_n^{k}, there is a monochromatic component of order at least knk+1\frac{kn}{k+1} and this is best possible for all nn. Recently, Guggiari and Scott and independently Rahimi proved a strengthening of the graph case in the result above which says that the same conclusion holds if KnK_n is replaced by any graph on nn vertices with minimum degree at least 5n61\frac{5n}{6}-1; furthermore, this bound on the minimum degree is best possible. We prove a strengthening of the k3k\geq 3 case in the result above which says that the same conclusion holds if KnkK_n^k is replaced by any kk-uniform hypergraph on nn vertices with minimum (k1)(k-1)-degree at least knk+1(k1)\frac{kn}{k+1}-(k-1); furthermore, this bound on the (k1)(k-1)-degree is best possible.

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Cite

@article{arxiv.2301.05806,
  title  = {Large monochromatic components in hypergraphs with large minimum codegree},
  author = {Deepak Bal and Louis DeBiasio},
  journal= {arXiv preprint arXiv:2301.05806},
  year   = {2023}
}

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5 pages