Albiac Alesanco, Fernando José

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https://academica-e.unavarra.es/handle/2454/48472

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Albiac Alesanco

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Fernando José

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Estadística, Informática y Matemáticas

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InaMat2. Instituto de Investigación en Materiales Avanzados y Matemáticas

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0000-0001-7051-9279

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88452

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504

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2022 - 20232
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Author: Berná, Pablo M. × Subject: Thresholding greedy algorithm ×

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Now showing 1 - 2 of 2
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    PublicationOpen Access
    Bidemocratic bases and their connections with other greedy-type bases
    (Springer, 2023) Albiac Alesanco, Fernando José; Ansorena, José L.; Berasategui, Miguel; Berná, Pablo M.; Lassalle, Silvia; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
    In nonlinear greedy approximation theory, bidemocratic bases have traditionally played the role of dualizing democratic, greedy, quasi-greedy, or almost greedy bases. In this article we shift the viewpoint and study them for their own sake, just as we would with any other kind of greedy-type bases. In particular we show that bidemocratic bases need not be quasi-greedy, despite the fact that they retain a strong unconditionality flavor which brings them very close to being quasi-greedy. Our constructive approach gives that for each 1 < p < infinity the space L-p has a bidemocratic basis which is not quasi-greedy. We also present a novel method for constructing conditional quasi-greedy bases which are bidemocratic, and provide a characterization of bidemocratic bases in terms of the new concepts of truncation quasi-greediness and partially demo-cratic bases.
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    PublicationOpen Access
    Weak forms of unconditionality of bases in greedy approximation
    (Instytut Matematyczny, 2022) Albiac Alesanco, Fernando José; Ansorena, José L.; Berasategui, Miguel; Berná, Pablo M.; Lassalle, Silvia; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika; Institute for Advanced Materials and Mathematics - INAMAT2
    We study a new class of bases, weaker than quasi-greedy bases, which retain their unconditionality properties and can provide the same optimality for the thresholding greedy algorithm. We measure how far these bases are from being unconditional and use this concept to give a new characterization of nearly unconditional bases.