Multicolor list Ramsey numbers grow exponentially

TL;DR

This paper proves that multicolor list Ramsey numbers grow exponentially with the number of colors if and only if the hypergraph is not r-partite, refining the understanding of their asymptotic behavior.

Contribution

It establishes a precise exponential growth rate for list Ramsey numbers based on the hypergraph's partiteness, resolving a key open question.

Findings

List Ramsey numbers grow exponentially for non-r-partite hypergraphs.

The growth rate is e^{Theta(k)} for such hypergraphs.

The result characterizes the growth behavior completely.

Abstract

The list Ramsey number $R_{\ell}(H,k)$, recently introduced by Alon, Buci\'c, Kalvari, Kuperwasser, and Szab\'o, is a list-coloring variant of the classical Ramsey number. They showed that if $H$ is a fixed $r$-uniform hypergraph that is not $r$-partite and the number of colors $k$ goes to infinity, $e^{\Omega(\sqrt{k})} \le R_{\ell} (H,k) \le e^{O(k)}$. We prove that $R_{\ell}(H,k) = e^{\Theta(k)}$ if and only if $H$ is not $r$-partite.