On class of Banach spaces
M. Valdivia (1977)
Studia Mathematica
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M. Valdivia (1977)
Studia Mathematica
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Anatolij M. Plichko, David Yost (2000)
Extracta Mathematicae
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Does a given Banach space have any non-trivial complemented subspaces? Usually, the answer is: yes, quite a lot. Sometimes the answer is: no, none at all.
David Yost (1997)
Extracta Mathematicae
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W. Szlenk (1968)
Studia Mathematica
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Marián Fabian, Gilles Godefroy (1988)
Studia Mathematica
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Godefroy, Gilles (2000)
Serdica Mathematical Journal
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We survey several applications of Simons’ inequality and state related open problems. We show that if a Banach space X has a strongly sub-differentiable norm, then every bounded weakly closed subset of X is an intersection of finite union of balls.
L. Vašák (1981)
Studia Mathematica
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Félix Cabello Sánchez, Jesús M. Fernández Castillo, David Yost (2000)
Extracta Mathematicae
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Sobczyk's theorem is usually stated as: . Nevertheless, our understanding is not complete until we also recall: . Now the limits of the phenomenon are set: although c is complemented in separable superspaces, it is not necessarily complemented in a non-separable superspace, such as l.
Gilles Godefroy, Vicente Montesinos, Václav Zizler (1995)
Commentationes Mathematicae Universitatis Carolinae
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The strong subdifferentiability of norms (i.eȯne-sided differentiability uniform in directions) is studied in connection with some structural properties of Banach spaces. It is shown that every separable Banach space with nonseparable dual admits a norm that is nowhere strongly subdifferentiable except at the origin. On the other hand, every Banach space with a strongly subdifferentiable norm is Asplund.