On Banach spaces that contain l1 as complemented subspace.(Spanish:Sobre los espacios de Banach que contienen a l1 como complementado).

Abstract

Let E and F be two Banach spaces, and let L(E,F) [WK(E,F)] denote the space of all continuous [weakly compact] linear operators from E to F. Obviously, if F is reflexive then L(E,F)=WK(E,F). The author proves that the equality L(E,F)=WK(E,F) implies the reflexivity of F if and only if E contains l1 as a complemented subspace. In the last part of the note she investigates when the space C(T,E) of all continuous functions on the compact space T with values in the Banach space E contains l1 as a complemented subspace.