Mathematical Theory of Computational Resolution Limit in Multi-dimensions

TL;DR

This paper extends the theory of computational resolution limits from one dimension to multi-dimensions, characterizing the fundamental limits of resolving point sources in noisy, band-limited Fourier data across various dimensions.

Contribution

It develops a multi-dimensional theory of computational resolution limits for number detection and support recovery, including phase transition phenomena and algorithms for practical verification.

Findings

Existence of phase transition in resolution capabilities based on super-resolution factor and SNR.

Verification of the theory through deterministic subspace projection algorithms in 2D and 3D.

Numerical results confirm the predicted phase transition phenomena.

Abstract

Resolving a linear combination of point sources from their band-limited Fourier data is a fundamental problem in imaging and signal processing. With the incomplete Fourier data and the inevitable noise in the measurement, there is a fundamental limit on the separation distance between point sources that can be resolved. This is the so-called resolution limit problem. Characterization of this resolution limit is still a long-standing puzzle despite the prevalent use of the classic Rayleigh limit. It is well-known that Rayleigh limit is heuristic and its drawbacks become prominent when dealing with data that is subjected to delicate processing, as is what modern computational imaging methods do. Therefore, more precise characterization of the resolution limit becomes increasingly necessary with the development of data processing methods. For this purpose, we developed a theory of "computational resolution limit" for both number detection and support recovery in one dimension in [arXiv:2003.02917[cs.IT], arXiv:1912.05430[eess.IV]]. In this paper, we extend the one-dimensional theory to multi-dimensions. More precisely, we define and quantitatively characterize the "computational resolution limit" for the number detection and support recovery problems in a general k-dimensional space. Our results indicate that there exists a phase transition phenomenon regarding to the super-resolution factor and the signal-to-noise ratio in each of the two recovery problems. Our main results are derived using a subspace projection strategy. Finally, to verify the theory, we proposed deterministic subspace projection based algorithms for the number detection and support recovery problems in dimension two and three. The numerical results confirm the phase transition phenomenon predicted by the theory.