The K-functional for rearrangement invariant spaces
Alberto Torchinsky (1979)
Studia Mathematica
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Alberto Torchinsky (1979)
Studia Mathematica
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Gunnar Sparr (1978)
Studia Mathematica
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Maria Carro (1994)
Studia Mathematica
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We develop a new method of real interpolation for infinite families of Banach spaces that covers the methods of Lions-Peetre, Sparr for N spaces, Fernández for spaces and the recent method of Cobos-Peetre.
María J. Carro (1994)
Collectanea Mathematica
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Mieczysław Mastyło, Vladimir Ovchinnikov (1997)
Studia Mathematica
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We study those compatible couples of Banach spaces for which the complex method interpolation spaces are also described by the K-method of interpolation. As an application we present counter-examples to Cwikel's conjecture that all interpolation spaces of a Banach couple are described by the K-method whenever all complex interpolation spaces have this property.
Yves Raynaud (1991)
Compositio Mathematica
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Fernando Cobos Díaz (1989)
Revista Matemática de la Universidad Complutense de Madrid
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The behavior of compactness under real interpolation real is discussed. Classical results due to Krasnoselskii, Lions-Peetre, Persson, and Hayakawa are described, as well as others obtained very recently by Edmunds, Potter, Fernández, and the author.
Fernando Cobos, Alba Segurado (2012)
Studia Mathematica
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We study limiting K- and J-methods for arbitrary Banach couples. They are related by duality and they extend the methods already known in the ordered case. We investigate the behaviour of compact operators and we also discuss the representation of the methods by means of the corresponding dual functional. Finally, some examples of limiting function spaces are given.
Rack, Heinz-Joachim, Vajda, Robert (2014)
Serdica Journal of Computing
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ACM Computing Classification System (1998): G.1.1, G.1.2. We consider optimal Lagrange interpolation with polynomials of degree at most two on the unit interval [−1, 1]. In a largely unknown paper, Schurer (1974, Stud. Sci. Math. Hung. 9, 77-79) has analytically described the infinitely many zero-symmetric and zero-asymmetric extremal node systems −1 ≤ x1 < x2 < x3 ≤ 1 which all lead to the minimal Lebesgue constant 1.25 that had already been determined by Bernstein...
Pustylnik, Evgeniy (1996)
Abstract and Applied Analysis
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Mario Milman (1993)
Collectanea Mathematica
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We give an extension of the commutator theorems of Jawerth, Rochberg and Weiss [9] for the real method of interpolation. The results are motivated by recent work by Iwaniek and Sbordone [6] on generalized Hodge decompositions. The main estimates of these authors are based on a commutator theorem for a specific operator acting on Lp spaces and through the use of the complex method of interpolation. In this note we give an extension of the Iwaniek-Sbordone theorem to general real interpolation...