A new characterization of the interpolation spaces between L... and L...
We complete a result of Hernandez on the complex interpolation for families of Banach lattices.
The splitting problem is studied for short exact sequences consisting of countable projective limits of DFN-spaces (*) 0 → F → X → G → 0, where F or G are isomorphic to the space of distributions D'. It is proved that every sequence (*) splits for F ≃ D' iff G is a subspace of D' and that, for ultrabornological F, every sequence (*) splits for G ≃ D' iff F is a quotient of D'
We review the main facts that are behind a unified construction for the commutator theorem of the main interpolation methods.