Year: 2026
Type: preprint
Abstract: Rudin's problem asks whether, in the unit ball of $\mathbb C^d$ with $d\ge2$ fixed, the Hardy space $H^2(\partial\mathbb B_d)$ admits a uniformly bounded orthonormal basis consisting of homogeneous holomorphic polynomials. For $d=2$ and $d=3$ the answer is due to Bourgain, but the general-dimensional case has remained open. This paper gives an affirmative answer to Rudin's problem in every fixed dimension. More precisely, we prove that there is an orthonormal basis consisting of homogeneous polynomials $\{p_j\}_{j=1}^\infty$ of $H^2(\partial\mathbb B_d)$ such that $$\|p_j\|_{L^\infty(\partial\mathbb B_d)}\leq \exp\left(\frac12d\log d+O(d)\right).$$ Here the implicit constant in $O(d)$ is independent of $d$ and $j$.
Source: arXiv (Cornell University)
Authors: Wang, Penghui, Zhang, Fan, Zhu, Zeyou
Language: English
Subfield: Applied Mathematics
Field: Mathematics
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7223217051