Listar por autor "Ansorena, José L."

Sparse approximation using new greedy-like bases in superreflexive spaces

Albiac Alesanco, Fernando José

; Ansorena, José L.; Berasategui, Miguel (Instytut Matematyczny, 2023) Artículo / Artikulua

This paper is devoted to theoretical aspects of optimality of sparse approximation. We undertake a quantitative study of new types of greedy-like bases that have recently arisen in the context of non-linear m-term approximation ...

Structure of the Lipschitz free p-spaces Fp(Zd) and Fp(Rd) for 0 < p ≤ 1

Albiac Alesanco, Fernando José

; Ansorena, José L.; Cúth, Marek; Doucha, Michal (Springer, 2021) Artículo / Artikulua

Our aim in this article is to contribute to the theory of Lipschitz free p-spaces for 0 < p ≤ 1 over the Euclidean spaces Rd and Zd. To that end, on one hand we show that Fp(Rd) admits a Schauder basis for every p ∈ 2 (0, ...

Unconditional and quasi-greedy bases in L-p with applications to Jacobi polynomials Fourier series

Albiac Alesanco, Fernando José

; Ansorena, José L.; Ciaurri, Óscar; Varona, Juan L. (European Mathematical Society, 2019) Artículo / Artikulua

We show that the decreasing rearrangement of the Fourier series with respect to the Jacobi polynomials for functions in L-p does not converge unless p = 2. As a by-product of our work on quasi-greedy bases in L-p(µ), we ...

Uniqueness of unconditional basis of Hp(T) ⊕ 2 and Hp(T) ⊕ T (2) for 0 < p < 1

Albiac Alesanco, Fernando José

; Ansorena, José L.; Wojtaszczyk, Przemyslaw (Elsevier, 2022) Artículo / Artikulua

Our goal in this paper is to advance the state of the art of the topic of uniqueness of unconditional basis. To that end we establish general conditions on a pair (X, Y) formed by a quasi-Banach space X and a Banach ...

Uniqueness of unconditional basis of infinite direct sums of quasi-Banach spaces

Albiac Alesanco, Fernando José

; Ansorena, José L. (Kluwer Academic Publishers, 2022) Artículo / Artikulua

This paper is devoted to providing a unifying approach to the study of the uniqueness of unconditional bases, up to equivalence and permutation, of infinite direct sums of quasi-Banach spaces. Our new approach to this type ...

Uniqueness of unconditional basis of ℓ2⊕T(2)

Albiac Alesanco, Fernando José

; Ansorena, José L. (American Mathematical Society, 2022) Artículo / Artikulua

We provide a new extension of Pitt’s theorem for compact operators between quasi-Banach lattices which permits to describe unconditional bases of finite direct sums of Banach spaces X1 · · · Xn as direct sums of unconditional ...

Weak forms of unconditionality of bases in greedy approximation

Albiac Alesanco, Fernando José

; Ansorena, José L.; Berasategui, Miguel; Berná, Pablo M.; Lassalle, Silvia (Instytut Matematyczny, 2022) Artículo / Artikulua

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 ...