Large monochromatic components in hypergraphs with large minimum codegree

Abstract

A result of Gyárfás says that for every $3$-coloring of the edges of the complete graph $K_n$, there is a monochromatic component of order at least $\frac{n}{2}$, and this is best possible when $4$ divides $n$. Furthermore, for all $k\ge 3$ and every $(k+1)$-coloring of the edges of the complete $k$-uniform hypergraph $K_n^k$, there is a monochromatic component of order at least $\frac{kn}{k+1}$ and this is best possible for all $n$. 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 $K_n$ is replaced by any graph on $n$ vertices with minimum degree at least $\frac{5n}{6}-1$; furthermore, this bound on the minimum degree is best possible. We prove a strengthening of the $k\ge 3$ case in the result above which says that the same conclusion holds if $K_n^k$ is replaced by any $k$-uniform hypergraph on $n$ vertices with minimum $(k-1)$-degree at least $\frac{kn}{k+1}-(k-1)$; furthermore, this bound on the $(k-1)$-degree is best possible.

5 pages