On the multicolor Ramsey number of a graph with m edges

Abstract

The multicolor Ramsey number $r_k(F)$ of a graph $F$ is the least integer $n$ such that in every coloring of the edges of $K_n$ by $k$ colors there is a monochromatic copy of $F$. In this short note we prove an upper bound on $r_k(F)$ for a graph $F$ with $m$ edges and no isolated vertices of the form $k^{6km^{2/3}}$ addressing a question of Sudakov [ Adv. Math. 227 (2011), no. 1, 601--609]. Furthermore, the constant in the exponent in the case of bipartite $F$ and two colors is lowered so that $r_2(F)\le 2^{(1+o(1))2\sqrt{2m}}$ improving the result of Alon, Krivelevich and Sudakov [Combin. Probab. Comput. 12 (2003), no. 5--6, 477--494].