Person: Cobos Díaz, Fernando
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First Name
Fernando
Last Name
Cobos Díaz
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Matemáticas
Department
Análisis Matemático Matemática Aplicada
Area
Análisis Matemático
Identifiers
8 results
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Now showing 1 - 8 of 8
Item Approximation and entropy numbers of embeddings between approximation spaces(Constructive Approximation, 2018) Cobos Díaz, Fernando; Domínguez Bonilla, Óscar; Kühn, ThomasItem On Besov spaces of logarithmic smoothness and Lipschitz spaces(Journal of Mathematical Analysis and Applications, 2015) Cobos Díaz, Fernando; Domínguez Bonilla, ÓscarWe compare Besov spaces B-p,q(0,b) with zero classical smoothness and logarithmic smoothness b defined by using the Fourier transform with the corresponding spaces:B-p,q(0,b) defined by means of the modulus of smoothness. In particular, we show that B-p,q(0,b+1/2) = B-2,2(0,b) for b > -1/2. We also determine the dual of In:B-p,q(0,b) with the help of logarithmic Lipschitz spaces Lip(p,q)((1,-alpha)) Finally we show embeddings between spaces Lip(p,q)((1,-alpha)) and B-p,q(1,b) which complement and improve embeddings established by Haroske (2000).Item On Besov spaces modelled on Zygmund spaces(Journal of Approximation Theory, 2016) Cobos Díaz, Fernando; Domínguez Bonilla, ÓscarWorking on the d-torus, we show that Besov spaces Bps(Lp(logL)a) modelled on Zygmund spaces can be described in terms of classical Besov spaces. Several other properties of spaces Bps(Lp(logL)a) are also established. In particular, in the critical case s=d/p, we characterize the embedding of Bpd/p(Lp(logL)a) into the space of continuous functions.Item On the Relationship Between Two Kinds of Besov Spaces with Smoothness Near Zero and Some Other Applications of Limiting Interpolation(Journal of Fourier Analysis and Applications, 2015) Cobos Díaz, Fernando; Domínguez Bonilla, ÓscarUsing limiting interpolation techniques we study the elationship between Besov spaces B0,−1/q p,q with zero classical smoothness and logarithmic smoothness −1/q defined by means of differences with similar spaces 0,b,d p,q defined by means of the Fourier transform. Among other things, we prove that B0,−1/2 2,2 = B0,0,1/2 2,2 . We also derive several results on periodic spaces B0,−1/q p,q (T), including embeddings in generalized Lorentz–Zygmund spaces and the distribution of Fourier coefficients of functions of B0,−1/q p,q (T).Item On nuclearity of embeddings between Besov spaces(Journal of Approximation Theory, 2018) Cobos Díaz, Fernando; Domínguez Bonilla, Óscar; Kühn, ThomasLet Bp,qs,α(Ω) be the Besov space with classical smoothness s and additional logarithmic smoothness of order α on a bounded Lipschitz domain Ω in Rd. For s1, s2 ∈ R, 1 ≤ p1, p2, q1, q2 ≤ ∞ and s1 − s2 = d − d(1/p2 − 1/p1)+, we show a sufficient condition on q1, q2 for nuclearity of embedding Bs1,α1 (superíndices) y p1, q1 (subíndices)(Ω) → Bp2,α2 (superíndice) y s2 q,2 (subíndices) (Ω). We also show that the condition is necessary in a wide range of parameters.Item Embeddings of Besov spaces of logarithmic smoothness(Studia Mathematica, 2014) Cobos Díaz, Fernando; Domínguez Bonilla, ÓscarThis paper deals with Besov spaces of logarithmic smoothness B-p,T(0,b) formed by periodic functions. We study embeddings of B-p,T(0,b) into Lorentz-Zygmund spaces L-p,L-q(log L)(beta). Our techniques rely on the approximation structure of B-p,T(0,b), Nikol'skii type inequalities, extrapolation properties of L-p,L-q(log L)(beta) and interpolation.Item Compact operators and approximation spaces(Colloquium mathematicum, 2014) Cobos Díaz, Fernando; Domínguez Bonilla, Óscar; Martínez, AntónWe investigate compact operators between approximation spaces, paying special attention to the limit case. Applications are given to embeddings between Besov spaces.Item Characterizations of logarithmic Besov spaces in terms of differences, Fourier-analytical decompositions, wavelets and semi-groups.(Journal of Functional Analysis, 2016) Cobos Díaz, Fernando; Domínguez Bonilla, Óscar; Triebel, HansWe work with Besov spaces Bp,q0,b defined by means of differences, with zero classical smoothness and logarithmic smoothness with exponent b. We characterize Bp,q0,b by means of Fourier-analytical decompositions, wavelets and semi-groups. We also compare those results with the well-known characterizations for classical Besov spaces Bp,qs.