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Ensembles de Rosenthal et propriété de Radon-Nikodym relative

Mohammad Daher (2009)

Annales de la faculté des sciences de Toulouse Mathématiques

Soient G un groupe abélien compact métrisable, Γ son groupe dual et Λ ⊂ Γ un ensemble de Rosenthal. Nous montrons que L Λ ∞ ( G , Y * ) = C Λ ( G , Y * ) , lorsque Y * est un espace de Banach ayant la propriété de Radon-Nikodym et C Λ ( G , Y * ) est faiblement séquentiellement complet. Nous en déduisons une condition suffisante pour que le produit de deux ensembles de Rosenthal en soit encore un pour le groupe produit. Ensuite nous introduisons la propriété de Radon-Nikodym relative R N - Λ , une généralisation de la propriété de Radon-Nikodym analytique....

Extension of multilinear operators on Banach spaces.

Félix Cabello Sánchez, R. García, I. Villanueva (2000)

Extracta Mathematicae

These notes deal with the extension of multilinear operators on Banach spaces. The organization of the paper is as follows. In the first section we study the extension of the product on a Banach algebra to the bidual and some related structures including modules and derivations. Tha approach is elementary and uses the classical Arens' technique. Actually most of the results of section 1 can be easily derived from section 2. In section 2 we consider the problem of extending multilinear forms on a...

Extremely non-complex Banach spaces

Miguel Martín, Javier Merí (2011)

Open Mathematics

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.

Fragmentability and compactness in C(K)-spaces

B. Cascales, G. Manjabacas, G. Vera (1998)

Studia Mathematica

Let K be a compact Hausdorff space, C p ( K ) the space of continuous functions on K endowed with the pointwise convergence topology, D ⊂ K a dense subset and t p ( D ) the topology in C(K) of pointwise convergence on D. It is proved that when C p ( K ) is Lindelöf the t p ( D ) -compact subsets of C(K) are fragmented by the supremum norm of C(K). As a consequence we obtain some Namioka type results and apply them to prove that if K is separable and C p ( K ) is Lindelöf, then K is metrizable if, and only if, there is a countable and dense...

Fréchet-spaces-valued measures and the AL-property.

S. Okada, W. J. Ricker (2003)

RACSAM

Associated with every vector measure m taking its values in a Fréchet space X is the space L1(m) of all m-integrable functions. It turns out that L1(m) is always a Fréchet lattice. We show that possession of the AL-property for the lattice L1(m) has some remarkable consequences for both the underlying Fréchet space X and the integration operator f → ∫ f dm.

Generalized first class selectors for upper semi-continuous set-valued maps in Banach spaces

R. W. Hansell, L. Oncina (2005)

Czechoslovak Mathematical Journal

In this paper we deal with weakly upper semi-continuous set-valued maps, taking arbitrary non-empty values, from a non-metric domain to a Banach space. We obtain selectors having the point of continuity property relative to the norm topology for a large class of compact spaces as a domain. Exact conditions under which the selector is of the first Borel class are also investigated.

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