An improvement on Furstenberg's intersection problem

Abstract

In this paper, we study a problem posed by Furstenberg on intersections between $\times 2, \times 3$ invariant sets. We present here a direct geometrical counting argument to revisit a theorem of Wu and Shmerkin. This argument can be used to obtain further improvements. For example, we show that if $A_2,A_3\subset [0,1]$ are closed and $\times 2, \times 3$ invariant respectively, assuming that $\dim A_2+\dim A_3<1$ then $A_2\cap (uA_3+v)$ is sparse (defined in this paper) and has box dimension zero uniformly with respect to the real parameters $u,v$ such that $u$ and $u^{-1}$ are both bounded away from $0$.