Functional Donoho-Elad-Gribonval-Nielsen-Fuchs Sparsity Theorem
K. Mahesh Krishna
TL;DR
The paper extends the classical DEGN sparsity theorem from Hilbert spaces to abstract Banach spaces by employing 1-approximate Schauder frames (1-ASF). It introduces the analysis/synthesis framework in Banach spaces, defines a Banach-space Null Space Property (NSP), and proves that, under a bound involving $\sup_{n\neq m}|f_n(\tau_m)|$, a sparse coefficient $c$ with $\|c\|_0$ below this threshold yields a unique $\ell^1$-minimizer (problem $P_1$) and unique $\ell^0$-minimizer (problem $P_0$) for representations $x=\theta_\tau c$. This functional sparsity theorem thereby generalizes the DEGN result to a broader class of spaces, enabling sparse recovery in Banach-space settings and broadening potential applications in functional analysis and signal processing.
Abstract
Celebrated breakthrough sparsity theorem obtained independently by Donoho and Elad \textit{[Proc. Natl. Acad. Sci. USA, 2003]} and Gribonval and Nielsen \textit{[IEEE Trans. Inform. Theory, 2003]} and Fuchs \textit{[IEEE Trans. Inform. Theory, 2004]} says that unique sparse solution to NP-Hard $\ell_0$-minimization problem can be obtained using unique solution to P-Type $\ell_1$-minimization problem. In this paper, we extend their result to abstract Banach spaces using 1-approximate Schauder frames. We notice that the `normalized' condition for Hilbert spaces can be generalized to a larger extent when we consider Banach spaces.
