Abstract

Let X be a non-reflexive Banach space such that X ∗ is separable. Let N be the set of all equivalent norms on X , equipped with the topology of uniform convergence on bounded subsets of X . We show that the subset Z of N consisting of Fréchet-differentiable norms whose dual norm is not strictly convex reduces any difference of analytic sets. It follows that Z is exactly a difference of analytic sets when N is equipped with the standard Effros–Borel structure. Our main lemma elucidates the topological structure of the norm-attaining linear forms when the norm of X is locally uniformly rotund