RT Journal Article T1 On a problem of Lions concerning real interpolation spaces. The quasi-Banach case A1 Cobos Díaz, Fernando A1 Cwikel, M. A1 Kühn, Thomas AB 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. PB Elsevier SN 0022-247X YR 2022 FD 2022-08-28 LK https://hdl.handle.net/20.500.14352/71924 UL https://hdl.handle.net/20.500.14352/71924 LA eng NO CRUE-CSIC (Acuerdos Transformativos 2022) NO Ministerio de Ciencia, Innovación y Universidades (España) DS Docta Complutense RD 7 abr 2025