Ultrapowers of Calderón-Lozanovskii interpolation spaces

AbstractWe show that ultrapowers of Calderón interpolation spaces of a couple of Banach lattices with non-trivial concavity are obtained by Calderón interpolation from the ultrapowers of the given lattices. More generally ultrapowers of Calderón-Lozanovskii interpolation spaces are ‘generalized Calderón-Lozanovskii intermediate spaces’ between the ultrapowers. These results are extended to the situation of a couple of Köthe function spaces without concavity assumption