Improved Bounds for the Freiman-Ruzsa Theorem

Abstract: Let $A$ be a finite subset of an abelian group $G$, and suppose that $|A+A|\leq K|A|$. We show that for any $ε>0$, there exists a constant $C_ε$ such that $A$ can be covered by at most $\exp(C_ε\log(2K)^{1+ε})$ translates of a convex coset progression with dimension at most $C_ε\log(2K)^{1+ε}$ and size at most $\exp(C_ε\log(2K)^{1+ε})|A|$. This falls just short of the Polynomial Freiman-Ruzsa conjecture, which asserts that this statement is true for $ε=0$, and improves on results of Sanders and Konyagin, who showed that this statement is true for all $ε>2$. To prove this result, we use a mixture of entropy methods and Fourier analysis.