On the c_0-extension property

Abstract: In this work we investigate the c_0-extension property. This property generalizes Sobczyk's theorem in the context of nonseparable Banach spaces. We prove that a sufficient condition for a Banach space to have this property is that its closed dual unit ball is weak-star monolithic. We also present several results about the c_0-extension property in the context of C(K) Banach spaces. An interesting result in the realm of C(K) spaces is that the existence of a Corson compactum K such that C(K) does not have the c_0-extension property is independent from the axioms of ZFC.