The continuity of Beurling density and Beurling dimension of spectra of a class of self-affine spectral measures
Zi-Yun Chen, Zhi-Yi Wu, Min-Min Zhang
TL;DR
The work addresses the Beurling-analytic structure of spectra for a class of self-affine spectral measures, showing that for the plane self-affine measure $\mu_{R,B}$ with $R=2102$ and $B=\{00,10\}$ the spectra can realize any Beurling dimension $t\in[0,1]$ simultaneously with any $t$-Beurling density $s\ge0$. The authors construct spectra $\Lambda_{t,s}$ via explicit $\Lambda_{A,\beta}$-type sets, controlling $\dim_{Be}$ through growth rates of a function $\beta$ and, when needed, adjusting the $t$-Beurling density with additional scaling choices; they also show the level sets of spectra at fixed $t$ are of continuum cardinality. A joint attainment result (Theorem MR3) is achieved by two explicit growth-modulation schemes for $\beta$, covering the cases $s=0$ and $0<s<\infty$. Collectively, the results extend intermediate-value phenomena known for Moran and similar measures to a concrete self-affine spectral measure, illuminating the fine structure of spectral sets in fractal harmonic analysis and suggesting avenues for broader generalizations.
Abstract
It is well-known that the Beurling dimension of the spectra of certain singularly continuous spectral measures possesses an intermediate property. In this paper, we establish that for a class of self-affine spectral measures $μ$, both the Beurling dimension and Beurling density of their spectra attain full flexibility simultaneously. Specifically, for any $t\in (0,\dim_H^w(\supp(μ))]$ and $s\in [0,\infty)$, there exists a spectrum $Λ:=Λ_{t,s}$ of $μ$ satisfying \[\dim_{Be}(Λ)=t\quad\text{and}\quad D_{t}^+(Λ)=s\] where $\dim_H^w$ denotes the pseudo Hausdorff dimension, $\dim_{Be}$ denotes the Beurling dimension and $D_{t}^+$ denotes the $t$-Beurling density. These results provide new insights into the structure of the spectra for a singularly continuous spectral measure.
