Información del autor
Autor Cobos, Fernando |
Documentos disponibles escritos por este autor (121)
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Bashir, Zia ; Cobos, Fernando ; Karadzhov, Georgi E. | Matematisk Institut, Universitetsparken NY Munkegade | 2014We prove optimal embeddings of Calderon spaces built-up over function spaces defined in R-n with the Lebesgue measure into generalized Holder-Zygmund spaces in the super-critical and critical cases.![]()
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In this note we announce optimal embeddings of Calderon spaces built-up over function spaces defined in R-n with the Lebesgue measure into generalized Holder-Zygmund spaces in the super-critical case.![]()
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We describe the behavior of ideal variations under interpolation methods associated to polygons.![]()
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Bernhardsson, Bo ; Cobos, Fernando ; Kühn, Tomas ; Mondoc, Daniel ; Peetre, Jaak | Estonian Academy of Sciences | 2006So far trilinear forms have mostly been considered in low dimensions, in particular the dimension two (binary) case, and when the ring of scalars K is either the real numbers R or the complex ones C. The main aim in both situations has been to d[...]![]()
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We investigate the behaviour by general J- and K-methods of certain closed operator ideals. In particular, the results apply to weakly compact operators, Rosenthal operators and Banach–Saks operators.![]()
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We prove that if T: A0 ? B0 is compact and T: A1 ? B1 is compact (or T: A1 ? B1 is bounded and, then given any ? and q with 0![]()
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The behaviour of compactness under real interpolation is discussed. Classical results due to Krasnosel’skii, Lions-Peetre, Persson and Hayakawa are described, as well as others obtained very recently by Edmunds, Potter, Fernández and the author![]()
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Let (A(0)A(1)) and (B-0,B-1) be couples of quasi-Banach spaces and let T be a linear operator. We prove that if T:A(0) --> B-0 is compact and T: A(1) --> B-1 is bounded, then T: (A(0),A(1))(theta,q) --> (B-0,B-1)(theta,q) is also compact. Som[...]![]()
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We prove a reiteration theorem for interpolation methods defined by means of polygons, and a Wolff theorem for the case when the polygon has 3 or 4 vertices. In particular, we establish a Wolff theorem for Fernandez' spaces, which settles a prob[...]![]()
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We study spaces generated by applying the interpolation methods defined by a polygon ? to an N-tuple of real interpolation spaces with respect to a fixed Banach couple {X, Y }. We show that if the interior point (?,?) of the polygon does not lie[...]![]()
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Cobos, Fernando ; Fernández-Cabrera, Luz M. ; Martínez, Antón | Real Academia Ciencias Exactas Físicas Y Naturales | 2006This note deals with interpolation methods dened by means of polygons. We show necessary and sufcient conditions for compactness of operators acting from a J-space into a K-space.![]()
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We show that the behaviour under interpolation of 5x-class operators is not as good as it was supposed to be. An interpolation formula for Hilbert-Schmidt operators is also established.![]()
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We estimate the ideal measure of certain interpolated operators in terms of the measure of their restrictions to the intersection. The dual situation is also studied.: Special attention is paid to the ideal of weakly compact operators.![]()
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We establish representation theorems in terms of finite rank operators for some operator ideals defined by approximation numbers. We also study the stability under tensor product of these ideals.![]()
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The authors establish a number of results concerning normed ideals of multilinear forms in Banach spaces which extend the theory of trace ideals of operators on Hilbert space to such multilinear forms. For example, it is shown that the dual of t[...]![]()
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We show that, expcept in the trivial case p^ ^Qn ^2, the Lorentz operator space S ¿y is not isomorphic to a subspace of S for 1![]()
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Cobos, Fernando ; Fernández-Cabrera, Luz M. ; Martínez, Antón ; Pustylnik, Evgeniy | Cambridge University Press | 2002We show that certain interpolation results for compact operators established by Cobos and co-workers cannot be extended to general closed operator ideals. We shall also characterize compactness of an embedding in terms of functions related to th[...]![]()
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We continue the research on reiteration results between interpolation methods associated to polygons and the. real method. Applications are given to N-tuples of function spaces, or spaces or hounded linear operators and Banach algebras.![]()
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The authors study the limit case L1,q of the Lorentz- space approximation number ideals Lp,q. It is shown, using a suitable bilinear interpolation theorem that the ideals L1,q are tensor-stable. Moreover a telescoping sum representation theorem [...]![]()
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We review several results of Kühn, Peetre and the author on Schatten-von Neumann classes of multilinear forms. We recall also some of the open problems in this field![]()
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We study the description by means of the J-functional of logarithmic interpolation spaces (A0, A1) 1, q, A in the category of the p-normed quasi-Banach couples (0