Displaying similar documents to “Involutions with fixed points in 2-Banach spaces.”

Banach spaces and bilipschitz maps

J. Väisälä (1992)

Studia Mathematica

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We show that a normed space E is a Banach space if and only if there is no bilipschitz map of E onto E ∖ {0}.

Extremely non-complex Banach spaces

Miguel Martín, Javier Merí (2011)

Open Mathematics

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A Banach space X is said to be an extremely non-complex space if the norm equality ∥Id +T 2∥ = 1+∥T 2∥ holds for every bounded linear operator T on X. We show that every extremely non-complex Banach space has positive numerical index, it does not have an unconditional basis and that the infimum of diameters of the slices of its unit ball is positive.

Daugavet centers and direct sums of Banach spaces

Tetiana Bosenko (2010)

Open Mathematics

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A linear continuous nonzero operator G: X → Y is a Daugavet center if every rank-1 operator T: X → Y satisfies ||G + T|| = ||G|| + ||T||. We study the case when either X or Y is a sum X 1⊕F X 2 of two Banach spaces X 1 and X 2 by some two-dimensional Banach space F. We completely describe the class of those F such that for some spaces X 1 and X 2 there exists a Daugavet center acting from X 1⊕F X 2, and the class of those F such that for some pair of spaces X 1 and X 2 there is a Daugavet...