On subspaces of Banach spaces where every functional has a unique norm-preserving extension

Eve Oja; Märt Põldvere

Studia Mathematica (1996)

  • Volume: 117, Issue: 3, page 289-306
  • ISSN: 0039-3223

Abstract

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Let X be a Banach space and Y a closed subspace. We obtain simple geometric characterizations of Phelps' property U for Y in X (that every continuous linear functional g ∈ Y* has a unique norm-preserving extension f ∈ X*), which do not use the dual space X*. This enables us to give an intrinsic geometric characterization of preduals of strictly convex spaces close to the Beauzamy-Maurey-Lima-Uttersrud criterion of smoothness. This also enables us to prove that the U-property of the subspace K(E,F) of compact operators from a Banach space E to a Banach space F in the corresponding space L(E,F) of all operators implies the U-property for F in F** whenever F is isomorphic to a quotient space of E.

How to cite

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Oja, Eve, and Põldvere, Märt. "On subspaces of Banach spaces where every functional has a unique norm-preserving extension." Studia Mathematica 117.3 (1996): 289-306. <http://eudml.org/doc/216257>.

@article{Oja1996,
abstract = {Let X be a Banach space and Y a closed subspace. We obtain simple geometric characterizations of Phelps' property U for Y in X (that every continuous linear functional g ∈ Y* has a unique norm-preserving extension f ∈ X*), which do not use the dual space X*. This enables us to give an intrinsic geometric characterization of preduals of strictly convex spaces close to the Beauzamy-Maurey-Lima-Uttersrud criterion of smoothness. This also enables us to prove that the U-property of the subspace K(E,F) of compact operators from a Banach space E to a Banach space F in the corresponding space L(E,F) of all operators implies the U-property for F in F** whenever F is isomorphic to a quotient space of E.},
author = {Oja, Eve, Põldvere, Märt},
journal = {Studia Mathematica},
keywords = {space of compact operators; Phelps' property; norm-preserving extension; dual space; Beauzamy-Maurey-Lima-Uttersrud criterion of smoothness; -property; quotient space},
language = {eng},
number = {3},
pages = {289-306},
title = {On subspaces of Banach spaces where every functional has a unique norm-preserving extension},
url = {http://eudml.org/doc/216257},
volume = {117},
year = {1996},
}

TY - JOUR
AU - Oja, Eve
AU - Põldvere, Märt
TI - On subspaces of Banach spaces where every functional has a unique norm-preserving extension
JO - Studia Mathematica
PY - 1996
VL - 117
IS - 3
SP - 289
EP - 306
AB - Let X be a Banach space and Y a closed subspace. We obtain simple geometric characterizations of Phelps' property U for Y in X (that every continuous linear functional g ∈ Y* has a unique norm-preserving extension f ∈ X*), which do not use the dual space X*. This enables us to give an intrinsic geometric characterization of preduals of strictly convex spaces close to the Beauzamy-Maurey-Lima-Uttersrud criterion of smoothness. This also enables us to prove that the U-property of the subspace K(E,F) of compact operators from a Banach space E to a Banach space F in the corresponding space L(E,F) of all operators implies the U-property for F in F** whenever F is isomorphic to a quotient space of E.
LA - eng
KW - space of compact operators; Phelps' property; norm-preserving extension; dual space; Beauzamy-Maurey-Lima-Uttersrud criterion of smoothness; -property; quotient space
UR - http://eudml.org/doc/216257
ER -

References

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