Further improving of upper bound on a geometric Ramsey problem

Abstract

We consider following geometric Ramsey problem: find the least dimension $n$ such that for any 2-coloring of edges of complete graph on the points $\{\pm 1{\}}^n$ there exists 4-vertex coplanar monochromatic clique. Problem was first analyzed by Graham and Rothschild and they gave an upper bound: $n\le F(F(F(F(F(F(F(12)))))))$, where $F(m)=2{\uparrow }^{m}3$. In 2014 Lavrov, Lee and Mackey greatly improved this result by giving upper bound $n<2\uparrow \uparrow \uparrow 6<F(5)$. In this paper we revisit their estimates and reduce upper bound to $n<2\uparrow \uparrow \uparrow 5$

3 pages