Bounds on the Threshold Ramsey Multiplicity of Ramsey Numbers with Many Colors

Abstract

The Ramsey number $R(s,t)$ is the least integer $n$ such that any coloring of the edges of $K_n$ with two colors produces either a monochromatic $K_s$ in one color or a monochromatic $K_t$ in the other. If $s=t$, we say that the Ramsey number $R(s,s)$ is diagonal. The threshold Ramsey multiplicity of a diagonal Ramsey number $R(s,s)$, denoted $m(s,s)$ or $m_2(s)$, is the smallest number of copies of a monochromatic $K_s$ that can be found in any coloring of the edges of $K_{R(s,s)}$. For instance, $m_2(2)=1$, $m_2(3)=2$, and $m_2(4)=9$. We derive upper bounds for multicolor, off-diagonal threshold Ramsey multiplicities. In the diagonal two-color case, the resulting bounds improve the elementary random-coloring estimate for $5\le s\le 8$. In particular, we recover the known value $m(3,3,3)=5$ and obtain the bound $m(3,3,4)\le 10$. We conclude with a general framework for seeking further improvements.

12 pages