On the dimension of $\hat{I}\pm {\hat{I}}^2$-sets

Abstract

We show that the Feng-Xiong lower bound of $1/2$ for the box dimension of $\hat{I}\pm {\hat{I}}^2$-sets is tight. We also study how much of an $\hat{I}\pm {\hat{I}}^2$-orbit ``carries the dimension'': deleting an arbitararily small positive density set of times can cause the box dimension to drop to zero, but the Assouad dimension cannot drop below $1/4$.

22 pages