On a problem of Lions concerning real interpolation spaces. The quasi-Banach case

We prove that, under a mild condition on a couple (A0;A1) of quasi-Banach spaces, all real interpolation spaces (A0;A1)θ,p with 0 < θ < 1 and 0 < p ≤ ∞ are different from each other. In the Banach case and for 1 ≤ p ≤ ∞ this was shown by Janson, Nilsson, Peetre and Zafran, thus solving an o...

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Detalles Bibliográficos
Autores: Cobos Díaz, Fernando, Cwikel, M., Kühn, Thomas
Tipo de recurso: artículo
Fecha de publicación:2022
País:España
Institución:Universidad Complutense de Madrid (UCM)
Repositorio:Docta Complutense
Idioma:inglés
OAI Identifier:oai:docta.ucm.es:20.500.14352/71924
Acceso en línea:https://hdl.handle.net/20.500.14352/71924
Access Level:acceso abierto
Palabra clave:517.98
Real interpolation
K-functional
Dependence on the parameters
Spaces of operators defined by approximation numbers.
Análisis funcional y teoría de operadores
Descripción
Sumario:We prove that, under a mild condition on a couple (A0;A1) of quasi-Banach spaces, all real interpolation spaces (A0;A1)θ,p with 0 < θ < 1 and 0 < p ≤ ∞ are different from each other. In the Banach case and for 1 ≤ p ≤ ∞ this was shown by Janson, Nilsson, Peetre and Zafran, thus solving an old problem posed by J.-L. Lions. Moreover, we give an application to certain spaces which are important objects in Operator Theory and which consist of bounded linear operators whose approximation numbers belong to Lorentz sequence spaces.