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On equivalent strictly G-convex renormings of Banach spaces

Nataliia Boyko (2010)

Open Mathematics

We study strictly G-convex renormings and extensions of strictly G-convex norms on Banach spaces. We prove that ℓω(Γ) space cannot be strictly G-convex renormed given Γ is uncountable and G is bounded and separable.

On ergodicity for operators with bounded resolvent in Banach spaces

Kirsti Mattila (2011)

Studia Mathematica

We prove results on ergodicity, i.e. on the property that the space is a direct sum of the kernel of an operator and the closure of its range, for closed linear operators A such that | | α ( α - A ) - 1 | | is uniformly bounded for all α > 0. We consider operators on Banach spaces which have the property that the space is complemented in its second dual space by a projection P. Results on ergodicity are obtained under a norm condition ||I - 2P|| ||I - Q|| < 2 where Q is a projection depending on the operator A....

On extreme points of Orlicz spaces with Orlicz norm.

Henryk Hudzik, Marek Wisla (1993)

Collectanea Mathematica

In the paper we consider a class of Orlicz spaces equipped with the Orlicz norm over a non-negative, complete and sigma-finite measure space (T,Sigma,mu), which covers, among others, Orlicz spaces isomorphic to L-infinite and the interpolation space L1 + L-infinite. We give some necessary conditions for a point x from the unit sphere to be extreme. Applying this characterization, in the case of an atomless measure mu, we find a description of the set of extreme points of L1 + L-infinite which corresponds...

On Gateaux differentiable bump functions

Francisco Hernández, Stanimir Troyanski (1996)

Studia Mathematica

It is shown that the order of Gateaux smoothness of bump functions on a wide class of Banach spaces with unconditional basis is not better than that of Fréchet differentiability. It is proved as well that in the separable case this order for Banach lattices satisfying a lower p-estimate for 1≤ p < 2 can be only slightly better.

On having a countable cover by sets of small local diameter

Nadezhda Ribarska (2000)

Studia Mathematica

A characterization of topological spaces admitting a countable cover by sets of small local diameter close in spirit to known characterizations of fragmentability is obtained. It is proved that if X and Y are Hausdorff compacta such that C(X) has an equivalent p-Kadec norm and C p ( Y ) has a countable cover by sets of small local norm diameter, then C p ( X × Y ) has a countable cover by sets of small local norm diameter as well.

On incomparability of Banach spaces

Manuel González, Antonio Martinón (1994)

Banach Center Publications

Several concepts of incomparability of Banach spaces have been considered in the literature, which allow one to describe some of the properties of the product of two Banach spaces as a juxtaposition of the corresponding properties of the factors. In this paper we study the relations between these concepts of incomparability, survey the main results and applications, and state some open problems.

On infinite dimensional uniform smoothness of Banach spaces

Stanisław Prus (1999)

Commentationes Mathematicae Universitatis Carolinae

An infinite dimensional counterpart of uniform smoothness is studied. It does not imply reflexivity, but we prove that it gives some l p -type estimates for finite dimensional decompositions, weak Banach-Saks property and the weak fixed point property.

Currently displaying 501 – 520 of 1093