Additive energy, uncertainty principle and signal recovery mechanisms

Abstract

Given a signal $f:G\to \mathbb{C}$, where $G$ is a finite abelian group, under what reasonable assumptions can we guarantee the exact recovery of $f$ from a proper subset of its Fourier coefficients? In 1989, Donoho and Stark established a result \cite{DS89} using the classical uncertainty principle, which states that $|\text{supp}(f)|\cdot |\text{supp}(\hat{f})|\ge |G|$ for any nonzero signal $f$. Another result, first proven by Santose and Symes \cite{SS86}, was based on the Logan phenomenon \cite{L65}. In particular, the result showcases how the $L^1$ and $L^2$ minimizing signals with matching Fourier frequencies often recovers the original signal. The purpose of this paper is to relate these recovery mechanisms to additive energy, a combinatorial measure denoted and defined by $$\Lambda (A)=\left|\left\{(x_1,x_2,x_3,x_4)\in A^4\mid x_1+x_2=x_3+x_4\right\}\right|,$$ where $A\subset {\mathbb{Z}}_N^d$. In the first part of this paper, we use combinatorial techniques to establish an improved variety of the uncertainty principle in terms of additive energy. In a similar fashion as the Donoho-Stark argument, we use this principle to establish an often stronger recovery condition. In the latter half of the paper, we invoke these combinatorial methods to demonstrate two $L^p$ minimizing recovery results.