Resonance between Cantor sets

Abstract

Let $C_a$ be the central Cantor set obtained by removing a central interval of length $1-2a$ from the unit interval, and continuing this process inductively on each of the remaining two intervals. We prove that if $\log b/\log a$ is irrational, then \[ \dim(C_a+C_b) = \min(\dim(C_a) + \dim(C_b),1), \] where $\dim$ is Hausdorff dimension. More generally, given two self-similar sets $K,K^{\prime }$ in $\RR$ and a scaling parameter $s>0$, if the dimension of the arithmetic sum $K+s{K}^{\prime }$ is strictly smaller than $\dim (K)+\dim (K^{\prime })\le 1$ (``geometric resonance''), then there exists $r<1$ such that all contraction ratios of the similitudes defining $K$ and $K^{\prime }$ are powers of $r$ (``algebraic resonance''). Our method also yields a new result on the projections of planar self-similar sets generated by an iterated function system that includes a scaled irrational rotation.

To appear in Ergodic Theory and Dynamical Systems. 24 pages, 2 figures

References in corpus (1)

• On the arithmetic sums of Cantor sets

Cited by in corpus (1)

• Measure theoretic structure of the sum of two affine Cantor sets