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A generalized Kahane-Khinchin inequality

S. Favorov (1998)

Studia Mathematica

The inequality ʃ l o g | a n e 2 π i φ n | d φ 1 d φ n C l o g ( | a n | 2 ) 1 / 2 with an absolute constant C, and similar ones, are extended to the case of a n belonging to an arbitrary normed space X and an arbitrary compact group of unitary operators on X instead of the operators of multiplication by e 2 π i φ .

A generalized projection decomposition in Orlicz-Bochner spaces

Henryk Hudzik, Ryszard Płuciennik, Yuwen Wang (2005)

Banach Center Publications

In this paper, a precise projection decomposition in reflexive, smooth and strictly convex Orlicz-Bochner spaces is given by the representation of the duality mapping. As an application, a representation of the metric projection operator on a closed hyperplane is presented.

A geometrical/combinatorical question with implications for the John-Nirenberg inequality for BMO functions

Michael Cwikel, Yoram Sagher, Pavel Shvartsman (2011)

Banach Center Publications

The first and last sections of this paper are intended for a general mathematical audience. In addition to some very brief remarks of a somewhat historical nature, we pose a rather simply formulated question in the realm of (discrete) geometry. This question has arisen in connection with a recently developed approach for studying various versions of the function space BMO. We describe that approach and the results that it gives. Special cases of one of our results give alternative proofs of the...

A Gowers tree like space and the space of its bounded linear operators

Giorgos Petsoulas, Theocharis Raikoftsalis (2009)

Studia Mathematica

The famous Gowers tree space is the first example of a space not containing c₀, ℓ₁ or a reflexive subspace. We present a space with a similar construction and prove that it is hereditarily indecomposable (HI) and has ℓ₂ as a quotient space. Furthermore, we show that every bounded linear operator on it is of the form λI + W where W is a weakly compact (hence strictly singular) operator.

A lower bound on the radius of analyticity of a power series in a real Banach space

Timothy Nguyen (2009)

Studia Mathematica

Let F be a power series centered at the origin in a real Banach space with radius of uniform convergence ϱ. We show that F is analytic in the open ball B of radius ϱ/√e, and furthermore, the Taylor series of F about any point a ∈ B converges uniformly within every closed ball centered at a contained in B.

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