Harmonic and Functional Analysis of Wavelet and Frame Expansions

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This project involves research and education activities in harmonic and functional analysis concerned with the mathematical theory of multi-dimensional wavelet and frame expansions. Wavelet and frame theory is not only mathematically interesting as a subject of study by itself, this area has also found many applications outside of pure mathematics ranging from applied and computational harmonic analysis to signal processing and data compression. Some well-known examples where wavelets are a key tool include the JPEG 2000 digital image standard and fingerprint compression for data storage. The broader impacts of this project include education and training of undergraduate and graduate students in the area of harmonic analysis and wavelets.This project aims to answer some of the most fundamental questions in wavelet and frame theory. One of the main research directions of the project is the development of techniques for the construction of well-localized orthogonal wavelets for large classes of non-isotropic expanding dilations. A closely related complementary topic is the study of wavelets for non-expanding dilations. The problem of characterizing dilations for which there exist minimally supported frequency (MSF) wavelets is connected to the geometry of numbers; more specifically, to the estimate on the number of lattice points of dilates of balls. An analogous problem of classifying dilations for which there exist well-localized wavelets has implications in the study of non-isotropic function spaces. Another direction of the project is the construction of frames with certain desired properties, such as prescribed norms and frame operator. This line of research is closely related to infinite dimensional generalizations of the Schur-Horn theorem. The problem of characterizing diagonals of self-adjoint operators not only has implications for frame theory, it has also been studied extensively in the setting of von Neumann algebras. Finally, the project involves investigating the breakthrough solution of the Kadison-Singer problem with the aim of improving its techniques and obtaining new results.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.