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Gabor frames, operator algebras, and quasicrystals (completed)

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About the project

In signal processing, periodic signals can be studied using Fourier series, where the basic building blocks are sine waves. However, when a signal changes substantially over time, such as a piece of music, different methods are needed. Gabor frames provide one such method. A Gabor frame allows for representations of a signal that emphasizes its frequency content at each point in time, similarly to how sheet music is written. When constructing a Gabor frame, a point set in the time-frequency plane needs to be specified. Gabor frames over lattice point sets enjoy a deep duality theory with connections to operator algebras and the representation theory of groups. For non-lattice point sets, these connections are less clear. The aim of this project is to fill this gap in the existing knowledge, associating operator algebras to Gabor frames over a class of point sets known as quasicrystals. In particular, a major goal is to prove existence results for Gabor frames over quasicrystals which generalize known results for lattices.

Financing

This project is financed by the Reseach Council of Norway. Funding ID: 314048

Publications

  • Enstad, Ulrik Bo Rufus & Velthoven, Jordy Timo Van (2025). Coherent systems over approximate lattices in amenable groups. Annales de l'Institut Fourier. ISSN 0373-0956. 75(6), p. 2293–2315. doi: 10.5802/aif.3687. Full text in Research Archive
  • Enstad, Ulrik Bo Rufus & Raum, Sven (2024). A dynamical approach to sampling and interpolation in unimodular groups. Transactions of the American Mathematical Society. ISSN 0002-9947. 378(3), p. 1975–2006. doi: 10.1090/tran/9326. Full text in Research Archive
  • Enstad, Ulrik Bo Rufus; Vilalta, Eduard & Thiel, Hannes (2024). Criteria for the Existence of Schwartz Gabor Frames Over Rational Lattices. arXiv.org. ISSN 2331-8422. 2025(5), p. 1–12. doi: 10.1093/imrn/rnaf038. Full text in Research Archive
  • Enstad, Ulrik Bo Rufus; Raum, Sven & Favre, Gabriel (2023). Free actions of polynomial growth Lie groups and classifiable C*-algebras. arXiv.org. ISSN 2331-8422. Full text in Research Archive
  • Enstad, Ulrik Bo Rufus & Velthoven, Jordy Timo Van (2023). Linear independence of coherent systems associated to lattices. arXiv.org. ISSN 2331-8422. Full text in Research Archive
  • Enstad, Ulrik Bo Rufus & Velthoven, Jordy Timo Van (2022). On sufficient density conditions for lattice orbits of relative discrete series. Archiv der Mathematik. ISSN 0003-889X. doi: 10.1007/s00013-022-01748-8. Full text in Research Archive
  • Bedos, Eric Christophe; Enstad, Ulrik Bo Rufus & Velthoven, Jordy Timo Van (2022). Smooth lattice orbits of nilpotent groups and strict comparison of projections. Journal of Functional Analysis. ISSN 0022-1236. 283(6). doi: 10.1016/j.jfa.2022.109572. Full text in Research Archive

View all works in NVA

View all works in NVA

Published Nov. 2, 2023 8:04 PM - Last modified Oct. 24, 2024 8:59 AM