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ALMOST FRÉCHET DIFFERENTIABILITY OF LIPSCHITZ MAPPINGS BETWEEN INFINITE-DIMENSIONAL BANACH SPACES

Published online by Cambridge University Press:  29 April 2002

WILLIAM B. JOHNSON
Affiliation:
Department of Mathematics, Texas A&M University, College Station, TX 77843, USA. [email protected]
JORAM LINDENSTRAUSS
Affiliation:
Institute of Mathematics, Hebrew University of Jerusalem, Jerusalem 91904, Israel. [email protected]
DAVID PREISS
Affiliation:
Department of Mathematics, University College London, Gower Street, London WC1E 6BT. [email protected]
GIDEON SCHECHTMAN
Affiliation:
Department of Mathematics, Weizmann Institute of Science, Rehovot 76100, Israel. [email protected]
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Abstract

We give several sufficient conditions on a pair of Banach spaces X and Y under which each Lipschitz mapping from a domain in X to Y has, for every $\epsilon > 0$, a point of $\epsilon$-Fréchet differentiability. Most of these conditions are stated in terms of the moduli of asymptotic smoothness and convexity, notions which have appeared in the literature under a variety of names. We prove, for example, that for $\infty > r > p \ge 1$, every Lipschitz mapping from a domain in an $\ell_r$-sum of finite-dimensional spaces into an $\ell_p$-sum of finite-dimensional spaces has, for every $\epsilon > 0$, a point of $\epsilon$-Fréchet differentiability, and that every Lipschitz mapping from an asymptotically uniformly smooth space to a finite-dimensional space has such points. The latter result improves, with a simpler proof, an earlier result of the second and third authors. We also survey some of the known results on the notions of asymptotic smoothness and convexity, prove some new properties, and present some new proofs of existing results.

2000 Mathematical Subject Classification: 46G05, 46T20.

Type
Research Article
Copyright
2002 London Mathematical Society

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