Strong Bounds for 3-Progressions

Abstract

We show that for some constant ${\hat{I}}^2>0$, any subset $A$ of integers $\{1,\dots ,N\}$ of size at least $2^{-O((\log N{)}^2)}\cdot N$ contains a non-trivial three-term arithmetic progression. Previously, three-term arithmetic progressions were known to exist only for sets of size at least $N/(\log N{)}^{1+c}$ for a constant $c>0$. Our approach is first to develop new analytic techniques for addressing some related questions in the finite-field setting and then to apply some analogous variants of these same techniques, suitably adapted for the more complicated setting of integers.