Falconer distance problem, additive energy and Cartesian products

A celebrated result due to Wolff says if $E$ is a compact subset of ${\Bbb R}^2$,thentheLebesguemeasureofthedistanceset$\Delta(E)={|x-y|: x,y \in E }$ispositiveiftheHausdorffdimensionof$E$isgreaterthan$\frac{4}{3}$\mathrm{.}Inthispaperweimprovethe$\frac{4}{3}$ barrier by a small exponent for Cartesian products. In higher dimensions, also in the context of Cartesian products, we reduce Erdogan’s $\frac{d}{2}+\frac{1}{3}$ exponent to $\frac{d^2}{2d-1}$. The proof uses a combination of Fourier analysis and additive comibinatorics.