Ramsey numbers for regular induced subgraphs

Abstract

A problem proposed by Erd\H{o}s, Fajtlowicz and Staton asks for the smallest $n$ for which every graph on $n$ vertices contains a regular induced subgraph of order at least $k$. A variation is to ask for a regular induced subgraph of order exactly $k$. In this paper we provide exact values for $k\le 5$ and lower bounds for $k=6$ and $k=7$. We also improve the general lower bound of Alon, Krivelevich and Sudakov [SIAM J. Disc. Math, 2008].