English

A note on the set $\boldsymbol{A(A+A)}$

Number Theory 2019-05-29 v2

Abstract

Let pp a large enough prime number. When AA is a subset of Fp{0}\mathbb{F}_p\smallsetminus\{0\} of cardinality A>(p+1)/3|A|> (p+1)/3, then an application of Cauchy-Davenport Theorem gives Fp{0}A(A+A)\mathbb{F}_p\smallsetminus\{0\}\subset A(A+A). In this note, we improve on this and we show that if A0.3051p|A|\ge 0.3051 p implies A(A+A)Fp{0}A(A+A)\supseteq\mathbb{F}_p\smallsetminus\{0\}. In the opposite direction we show that there exists a set AA such that A>(1/8+o(1))p|A| > (1/8+o(1))p and Fp{0}⊈A(A+A)\mathbb{F}_p\smallsetminus\{0\}\not\subseteq A(A+A).

Keywords

Cite

@article{arxiv.1811.08869,
  title  = {A note on the set $\boldsymbol{A(A+A)}$},
  author = {Pierre-Yves Bienvenu and François Hennecart and Ilya Shkredov},
  journal= {arXiv preprint arXiv:1811.08869},
  year   = {2019}
}

Comments

10 pages

R2 v1 2026-06-23T05:23:46.823Z