On van Kampen-Flores, Conway-Gordon-Sachs and Radon theorems

Abstract

We exhibit relations between van Kampen-Flores, Conway-Gordon-Sachs and Radon theorems, by presenting direct proofs of some implications between them. The key idea is an interesting relation between the van Kampen and the Conway-Gordon-Sachs numbers for restrictions of a map of $(d+2)$-simplex to $\mathbb R^d$ to the $(d+1)$-face and to the $[d/2]$-skeleton.