{ "id": "1307.5466", "version": "v3", "published": "2013-07-20T21:32:17.000Z", "updated": "2017-01-10T13:24:55.000Z", "title": "Compactness in quasi-Banach function spaces and applications to compact embeddings of Besov-type spaces", "authors": [ "António Caetano", "Amiran Gogatishvili", "Bohumír Opic" ], "comment": "24 pages", "journal": "Proceedings of the Royal Society of Edinburgh, Section A, Mathematics, 146 (2016), 905-927", "doi": "10.1017/S0308210515000761", "categories": [ "math.FA" ], "abstract": "There are two main aims of the paper. The first one is to extend the criterion for the precompactness of sets in Banach function spaces to the setting of quasi-Banach function spaces. The second one is to extend the criterion for the precompactness of sets in the Lebesgue spaces $L_p(\\mathbb R^n)$, $1 \\leq p < \\infty$, to the so-called power quasi-Banach function spaces. These criteria are applied to establish compact embeddings of abstract Besov spaces into quasi-Banach function spaces. The results are illustrated on embeddings of Besov spaces $B^s_{p,q}(\\mathbb R^n)$, $0