SPECTRALITY AND NON-SPECTRALITY OF PLANAR SELF-SIMILAR MEASURES WITH FOUR-ELEMENT DIGIT SETS
Abstract
Let II be the unit matrix and D={(00),(10),(01),(−1−1)}. In this paper, we consider the self-similar measure μρI,D on ℝ2 generated by the iterated function system {ϕd(x)=ρI(x+d)}d∈D where 0<|ρ|<1. We prove that there exists Λ such that EΛ={e2πi<λ,x>:λ∈Λ} is an orthonormal basis for L2(μρI,D) if and only if |ρ|=1/(2q) for some integer q>0.