Large sets without Fourier restriction theorems

TL;DR

This paper constructs a function in all L^p spaces with a Fourier transform lacking Lebesgue points on a full Hausdorff dimension Cantor set, demonstrating limitations of Fourier restriction theorems on fractal sets.

Contribution

It introduces a function with specific Fourier properties and shows the failure of Fourier restriction relations on fractal sets, challenging existing conjectures.

Findings

Constructed a function in all L^p spaces with Fourier transform lacking Lebesgue points on a full-dimensional Cantor set.

Proved that certain fractal sets are avoided by measures satisfying Fourier restriction theorems.

Demonstrated the lack of a direct relation between Hausdorff dimension and Fourier restriction exponents.

Abstract

We construct a function that lies in $L^p(\mathbb{R}^d)$ for every $p \in (1,\infty]$ and whose Fourier transform has no Lebesgue points in a Cantor set of full Hausdorff dimension. We apply Kova\v{c}'s maximal restriction principle to show that the same full-dimensional set is avoided by any Borel measure satisfying a nontrivial Fourier restriction theorem. As a consequence of a near-optimal fractal restriction theorem of {\L}aba and Wang, we hence prove a lack of valid relations between the Hausdorff dimension of a set and the range of possible Fourier restriction exponents for measures supported in the set.