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Description of quotient algebras in function algebras containing continuous unbounded functions

Mati Abel, Jorma Arhippainen, Jukka Kauppi (2012)

Open Mathematics

Let X be a completely regular Hausdorff space, 𝔖 a cover of X, and C b ( X , 𝕂 ; 𝔖 ) the algebra of all 𝕂 -valued continuous functions on X which are bounded on every S 𝔖 . A description of quotient algebras of C b ( X , 𝕂 ; 𝔖 ) is given with respect to the topologies of uniform and strict convergence on the elements of 𝔖 .

Description of the lack of compactness for the Sobolev imbedding

P. Gérard (2010)

ESAIM: Control, Optimisation and Calculus of Variations

We prove that any bounded sequence in a Hilbert homogeneous Sobolev space has a subsequence which can be decomposed as an almost-orthogonal sum of a sequence going strongly to zero in the corresponding Lebesgue space, and of a superposition of terms obtained from fixed profiles by applying sequences of translations and dilations. This decomposition contains in particular the various versions of the concentration-compactness principle.

Description of the lack of compactness of some critical Sobolev embedding

Hajer Bahouri (2011)

Journées Équations aux dérivées partielles

In this text, we present two recent results on the characterization of the lack of compactness of some critical Sobolev embedding. The first one derived in [5] deals with an abstract framework including Sobolev, Besov, Triebel-Lizorkin, Lorentz, Hölder and BMO spaces. The second one established in [3] concerns the lack of compactness of H 1 ( 2 ) into the Orlicz space. Although the two results are expressed in the same manner (by means of defect measures) and rely on the defect of compactness due to concentration...

Descriptive compact spaces and renorming

L. Oncina, M. Raja (2004)

Studia Mathematica

We study the class of descriptive compact spaces, the Banach spaces generated by descriptive compact subsets and their relation to renorming problems.

Descriptive properties of elements of biduals of Banach spaces

Pavel Ludvík, Jiří Spurný (2012)

Studia Mathematica

If E is a Banach space, any element x** in its bidual E** is an affine function on the dual unit ball B E * that might possess a variety of descriptive properties with respect to the weak* topology. We prove several results showing that descriptive properties of x** are quite often determined by the behaviour of x** on the set of extreme points of B E * , generalizing thus results of J. Saint Raymond and F. Jellett. We also prove a result on the relation between Baire classes and intrinsic Baire classes...

Descriptive Sets and the Topology of Nonseparable Banach Spaces

Hansell, R. (2001)

Serdica Mathematical Journal

This paper was extensively circulated in manuscript form beginning in the Summer of 1989. It is being published here for the first time in its original form except for minor corrections, updated references and some concluding comments.

Determinacy of adversarial Gowers games

Christian Rosendal (2014)

Fundamenta Mathematicae

We prove a game-theoretic dichotomy for G δ σ sets of block sequences in vector spaces that extends, on the one hand, the block Ramsey theorem of W. T. Gowers proved for analytic sets of block sequences and, on the other hand, M. Davis’ proof of Σ⁰₃ determinacy.

Déterminant associé à une trace sur une algèbre de Banach

Pierre de La Harpe, Georges Skandalis (1984)

Annales de l'institut Fourier

Soient A une algèbre de Banach complexe, G L ( A ) le groupe général linéaire stable de A et G L 0 ( A ) sa composante connexe pour la topologie normique. Nous montrons que toute trace non nulle r : A C permet de définir un homomorphisme Δ r de G L 0 ( A ) sur le quotient du groupe additif C par l’image r _ ( K 0 ( A ) ) du groupe de Grothendieck de A . Si A = M n ( C ) (respectivement si A est un facteur fini continu) avec la trace usuelle, alors exp ( i 2 π Δ r ) est le déterminant usuel (resp. exp ( Re ( i 2 π Δ r ) ) est celui de Fuglede et Kadison). Dans le cas général, les déterminants Δ r permettent...

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