UNIFORM SMOOTHNESS ENTAILS HAHN-BANACH

Original Articles

UNIFORM SMOOTHNESS ENTAILS HAHN-BANACH

Published in: Quaestiones Mathematicae
Volume 24 , issue 4 , 2001 , pages: 425–439
DOI: 10.1080/16073606.2001.9639231
Author(s): Edmond Albius ERMIT, Département de Mathématiques et Informatique, France , Marianne Morillon ERMIT, Département de Mathématiques et Informatique, France

Abstract

We show in set theory ZF (without the Axiom of Choice), that uniformly smooth normed spaces satisfy an effective and geometric form of the Hahn-Banach property. We also compare in ZF the two notions of Gâteaux differentiability and smoothness of a norm, and we obtain a new equivalent of the Hahn-Banach axiom.

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