Revista Matemática Complutense

, Volume 26, Issue 1, pp 33-55

First online:

Open Access This content is freely available online to anyone, anywhere at any time.

On interpolation of cocompact imbeddings

  • Michael CwikelAffiliated withDepartment of Mathematics, Technion–Israel Institute of Technology
  • , Kyril TintarevAffiliated withDepartment of Mathematics, Uppsala University Email author 


Cocompactness is a useful weaker counterpart of compactness in the study of imbeddings between function spaces. In this paper we prove that, under quite general conditions, cocompactness of imbeddings of Banach spaces persists under both real and complex interpolation. As an application, we obtain that subcritical continuous imbeddings of fractional Sobolev spaces and Besov spaces are cocompact relative to lattice shifts. We deduce this by interpolating the known cocompact imbeddings for classical Sobolev spaces (“vanishing” lemmas of Lieb and Lions). We also apply cocompactness to prove compactness of imbeddings of some radial subspaces and to show the existence of minimizers in some isoperimetric problems. Our research complements a range of previous results, and recalls that there is a natural conceptual framework for unifying them.


Besov spaces Cocompact imbeddings Concentration compactness Fractional Sobolev spaces Interpolation spaces Minimizers Mollifiers Sobolev imbeddings

Mathematics Subject Classification (2000)

46B70 46E35 46B50 30H25 46N20 49J45