On Arithmetic Progressions in Symmetric Sets in Finite Field Model

  • Jan Hązła


We consider two problems regarding arithmetic progressions in symmetric sets in the finite field (product space) model. First, we show that a symmetric set $S \subseteq \mathbb{Z}_q^n$ containing $|S| = \mu \cdot q^n$ elements must contain at least $\delta(q, \mu) \cdot q^n \cdot 2^n$ arithmetic progressions $x, x+d, \ldots, x+(q-1)\cdot d$ such that the difference $d$ is restricted to lie in $\{0,1\}^n$. Second, we show that for prime $p$ a symmetric set $S\subseteq\mathbb{F}_p^n$ with $|S|=\mu\cdot p^n$ elements contains at least $\mu^{C(p)}\cdot p^{2n}$ arithmetic progressions of length $p$. This establishes that the qualitative behavior of longer arithmetic progressions in symmetric sets is the same as for progressions of length three.

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