English

Fourier transform of self-affine measures

Dynamical Systems 2021-01-01 v2 Classical Analysis and ODEs Group Theory Probability

Abstract

Suppose FF is a self-affine set on Rd\mathbb{R}^d, d2d\geq 2, which is not a singleton, associated to affine contractions fj=Aj+bjf_j = A_j + b_j, AjGL(d,R)A_j \in \mathrm{GL}(d,\mathbb{R}), bjRdb_j \in \mathbb{R}^d, jAj \in \mathcal{A}, for some finite A\mathcal{A}. We prove that if the group Γ\Gamma generated by the matrices AjA_j, jAj \in \mathcal{A}, forms a proximal and totally irreducible subgroup of GL(d,R)\mathrm{GL}(d,\mathbb{R}), then any self-affine measure μ=pjfjμ\mu = \sum p_j f_j \mu, pj=1\sum p_j = 1, 0<pj<10 < p_j < 1, jAj \in \mathcal{A}, on FF is a Rajchman measure: the Fourier transform μ^(ξ)0\widehat{\mu}(\xi) \to 0 as ξ|\xi| \to \infty. As an application this shows that self-affine sets with proximal and totally irreducible linear parts are sets of rectangular multiplicity for multiple trigonometric series. Moreover, if the Zariski closure of Γ\Gamma is connected real split Lie group in the Zariski topology, then μ^(ξ)\widehat{\mu}(\xi) has a power decay at infinity. Hence μ\mu is LpL^p improving for all 1<p<1 < p < \infty and FF has positive Fourier dimension. In dimension d=2,3d = 2,3 the irreducibility of Γ\Gamma and non-compactness of the image of Γ\Gamma in PGL(d,R)\mathrm{PGL}(d,\mathbb{R}) is enough for power decay of μ^\widehat{\mu}. The proof is based on quantitative renewal theorems for random walks on the sphere Sd1\mathbb{S}^{d-1}.

Keywords

Cite

@article{arxiv.1903.09601,
  title  = {Fourier transform of self-affine measures},
  author = {Jialun Li and Tuomas Sahlsten},
  journal= {arXiv preprint arXiv:1903.09601},
  year   = {2021}
}

Comments

v2: 27 pages, updated references. Accepted to Advances in Math

R2 v1 2026-06-23T08:16:33.552Z