Dérivées intermédiaires dans les espaces de Hilbert pondérés. Application au comportement à l’ des solutions des équations d’évolution
Let X be a completely regular Hausdorff space, a cover of X, and the algebra of all -valued continuous functions on X which are bounded on every . A description of quotient algebras of is given with respect to the topologies of uniform and strict convergence on the elements of .
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.
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 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...
We study the class of descriptive compact spaces, the Banach spaces generated by descriptive compact subsets and their relation to renorming problems.
If E is a Banach space, any element x** in its bidual E** is an affine function on the dual unit ball 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 , 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...
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.
We prove a game-theoretic dichotomy for 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.
Soient une algèbre de Banach complexe, le groupe général linéaire stable de et sa composante connexe pour la topologie normique. Nous montrons que toute trace non nulle permet de définir un homomorphisme de sur le quotient du groupe additif par l’image du groupe de Grothendieck de . Si (respectivement si est un facteur fini continu) avec la trace usuelle, alors est le déterminant usuel (resp. est celui de Fuglede et Kadison). Dans le cas général, les déterminants permettent...