A note on the Fourier magnitude data and Sobolev embeddings

TL;DR

This paper investigates the stability of Fourier phase retrieval in Sobolev spaces, providing sharper estimates and removing extraneous terms, thereby advancing understanding of the problem's mathematical structure.

Contribution

It introduces improved stability estimates for Fourier phase retrieval in Sobolev spaces, refining previous results and eliminating additional imaginary terms.

Findings

Sharper stability constants achieved

Removal of additional imaginary term

Enhanced understanding of non-uniqueness in phase retrieval

Abstract

We study Sobolev $H^s(\mathbb{R}^n)$, $s \in \mathbb{R}$, stability of the Fourier phase problem to recover $f$ from the knowledge of $|\hat{f}|$ with an additional Bessel potential $H^{t,p}(\mathbb{R}^n)$ a priori estimate when $t \in \mathbb{R}$ and $p \in [1,2]$. These estimates are related to the ones studied recently by Steinerberger in "On the stability of Fourier phase retrieval" J. Fourier Anal. Appl., 28(2):29, 2022. While our estimates in general are different, they share some comparable special cases and the main improvement given here is that we can remove an additional imaginary term and obtain sharper constants. We also consider these estimates for the quotient distances related to the non-uniqueness of the Fourier phase problem. Our arguments closely follow the Fourier analysis proof of the Sobolev embeddings for Bessel potential spaces with minor modifications.