A blurred view of Van der Waerden type theorems

Abstract

Let $A{P}_k=\{a,a+d,\dots ,a+(k-1)d\}$ be an arithmetic progression. For $\epsilon >0$ we call a set $A{P}_k(\epsilon )=\{x_0,\dots ,x_{k-1}\}$ an $\epsilon$-approximate arithmetic progression if for some $a$ and $d$, $|x_i-(a+id)|<\epsilon d$ holds for all $i\in \{0,1\dots ,k-1\}$. Complementing earlier results of Dumitrescu, in this paper we study numerical aspects of Van der Waerden, Szemeredi and Furstenberg-Katznelson like results in which arithmetic progressions and their higher dimensional extensions are replaced by their $\epsilon$-approximation.

20 pages. Comments are welcome