On the density of Kravitz sets

Vsevolod Lev, Máté Matolcsi, Péter Pál Pach +1

We show that for a subset $A$ of the cyclic group of prime order $p>3$, if the sumset $A+A-2A$ is not the whole group, then $|A|\le \frac{2}{7}p$. Besides combinatorial arguments, we…