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Main Title: α-Molecules
Author(s): Grohs, Philipp
Keiper, Sandra
Kutyniok, Gitta
Schäfer, Martin
Type: Research Paper
Abstract: Within the area of applied harmonic analysis, various multiscale systems such as wavelets, ridgelets, curvelets, and shearlets have been introduced and successfully applied. The key property of each of those systems are their (optimal) approximation properties in terms of the decay of the L2-error of the best N-term approximation for a certain class of functions. In this paper, we introduce the general framework of α-molecules, which encompasses most multiscale systems from applied harmonic analysis, in particular, wavelets, ridgelets, curvelets, and shearlets as well as extensions of such with α being a parameter measuring the degree of anisotropy, as a means to allow a unified treatment of approximation results within this area. Based on an α-scaled index distance, we first prove that two systems of α-molecules are almost orthogonal. This leads to a general methodology to transfer approximation results within this framework, provided that certain consistency and time-frequency localization conditions of the involved systems of α-molecules are satisfied. We finally utilize these results to enable the derivation of optimal sparse approximation results for a specific class of cartoon-like functions by sufficient conditions on the 'control' parameters of a system of α-molecules.
Subject(s): anisotropic scaling
nonlinear approximation
sparsity equivalence
Issue Date: 10-Oct-2014
Date Available: 17-Dec-2021
Language Code: en
DDC Class: 510 Mathematik
MSC 2000: 42C40 Wavelets
41A25 Rate of convergence, degree of approximation
Series: Preprint-Reihe des Instituts für Mathematik, Technische Universität Berlin
Series Number: 2014, 25
ISSN: 2197-8085
TU Affiliation(s): Fak. 2 Mathematik und Naturwissenschaften » Inst. Mathematik
Appears in Collections:Technische Universität Berlin » Publications

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