English

Spectrality of random convolutions generated by finitely many Hadamard triples

Classical Analysis and ODEs 2024-01-09 v3 Functional Analysis

Abstract

Let {(Nj,Bj,Lj):1jm}\{(N_j, B_j, L_j): 1 \le j \le m\} be finitely many Hadamard triples in R\mathbb{R}. Given a sequence of positive integers {nk}k=1\{n_k\}_{k=1}^\infty and ω=(ωk)k=1{1,2,,m}N\omega=(\omega_k)_{k=1}^\infty \in \{1,2,\cdots, m\}^\mathbb{N}, let μω,{nk}\mu_{\omega,\{n_k\}} be the infinite convolution given by μω,{nk}=δNω1n1Bω1δNω1n1Nω2n2Bω2δNω1n1Nω2n2NωknkBωk.\mu_{\omega,\{n_k\}} = \delta_{N_{\omega_1}^{-n_1} B_{\omega_1}} * \delta_{N_{\omega_1}^{-n_1} N_{\omega_2}^{-n_2} B_{\omega_2}} * \cdots * \delta_{N_{\omega_1}^{-n_1} N_{\omega_2}^{-n_2} \cdots N_{\omega_k}^{-n_k} B_{\omega_k} }* \cdots. In order to study the spectrality of μω,{nk}\mu_{\omega,\{ n_k\}}, we first show the spectrality of general infinite convolutions generated by Hadamard triples under the equi-positivity condition. Then by using the integral periodic zero set of Fourier transform we show that if gcd(BjBj)=1\mathrm{gcd}(B_j - B_j)=1 for 1jm1 \le j \le m, then all infinite convolutions μω,{nk}\mu_{\omega,\{n_k\}} are spectral measures. This implies that we may find a subset Λω,{nk}R\Lambda_{\omega,\{n_k\}}\subseteq \mathbb{R} such that {eλ(x)=e2πiλx:λΛω,{nk}}\big\{ e_\lambda(x) = e^{2\pi i \lambda x}: \lambda \in \Lambda_{\omega,\{n_k\}} \big\} forms an orthonormal basis for L2(μω,{nk})L^2(\mu_{\omega,\{ n_k\}}).

Keywords

Cite

@article{arxiv.2203.11619,
  title  = {Spectrality of random convolutions generated by finitely many Hadamard triples},
  author = {Wenxia Li and Jun Jie Miao and Zhiqiang Wang},
  journal= {arXiv preprint arXiv:2203.11619},
  year   = {2024}
}

Comments

21 pages; final version