English

Extractors in Paley graphs: a random model

Combinatorics 2015-12-18 v2 Number Theory

Abstract

A well-known conjecture in analytic number theory states that for every pair of sets X,YZ/pZX,Y\subset\mathbb{Z}/p\mathbb{Z}, each of size at least logCp\log ^C p (for some constant CC) we have that the number of pairs (x,y)X×Y(x,y)\in X\times Y such that x+yx+y is a quadratic residue modulo pp differs from 12XY\frac12|X||Y| by o(XY)o\left(|X||Y|\right). We address the probabilistic analogue of this question, that is for every fixed δ>0\delta>0, given a finite group GG and AGA\subset G a random subset of density 12\frac12, we prove that with high probability for all subsets X,Ylog2+δG|X|,|Y|\geq \log ^{2+\delta} |G|, the number of pairs (x,y)X×Y(x,y)\in X\times Y such that xyAxy\in A differs from 12XY\frac12|X||Y| by o(XY)o\left(|X||Y|\right).

Keywords

Cite

@article{arxiv.1510.05998,
  title  = {Extractors in Paley graphs: a random model},
  author = {Rudi Mrazović},
  journal= {arXiv preprint arXiv:1510.05998},
  year   = {2015}
}

Comments

12 pages. To appear in the European Journal of Combinatorics. This is the version accepted for publication, incorporating the referees' suggestions

R2 v1 2026-06-22T11:24:56.544Z