Idéaux fermés de fonctions (fin)
The structure of closed ideals of a regular algebra containing the classical A∞ is considered. Several division and approximation results are proved and a characterization of those ideals whose intersection with A∞ is not {0} is obtained. A complete description of the ideals with countable hull is given, with applications to synthesis of hyperfunctions.
We find an analytic formulation of the notion of Hopf image, in terms of the associated idempotent state. More precisely, if π:A → Mₙ(ℂ) is a finite-dimensional representation of a Hopf C*-algebra, we prove that the idempotent state associated to its Hopf image A' must be the convolution Cesàro limit of the linear functional φ = tr ∘ π. We then discuss some consequences of this result, notably to inner linearity questions.
Using the holomorphic functional calculus we give a characterization of idempotent elements commuting with a given element in a Banach algebra.
Let be the Beurling algebra with weight on the unit circle and, for a closed set , let . We prove that, for , there exists a closed set of measure zero such that the quotient algebra is not generated by its idempotents, thus contrasting a result of Zouakia. Furthermore, for the Lipschitz algebras and the algebra of absolutely continuous functions on , we characterize the closed sets for which the restriction algebras and are generated by their idempotents.
We propose the study of some questions related to the Dunkl-Hermite semigroup. Essentially, we characterize the images of the Dunkl-Hermite-Sobolev space, and , , under the Dunkl-Hermite semigroup. Also, we consider the image of the space of tempered distributions and we give Paley-Wiener type theorems for the transforms given by the Dunkl-Hermite semigroup.
In questo articolo vengono date alcune varianti del teorema di immersione di Sobolev in spazi di Lorentz. In particolare si dimostra un teorema di immersione per spazi di Sobolev anisotropi supponendo che le derivate parziali appartengono a spazi di Lorentz diversi, anche nel caso limite, corrispondente all’estensione di Brezis-Wainger del teorema di Trudinger per .
This paper is devoted to the study of a turbulent circulation model. Equations are derived from the “Navier-Stokes turbulent kinetic energy” system. Some simplifications are performed but attention is focused on non linearities linked to turbulent eddy viscosity . The mixing length acts as a parameter which controls the turbulent part in . The main theoretical results that we have obtained concern the uniqueness of the solution for bounded eddy viscosities and small values of and its asymptotic...
This paper is devoted to the study of a turbulent circulation model. Equations are derived from the “Navier-Stokes turbulent kinetic energy” system. Some simplifications are performed but attention is focused on non linearities linked to turbulent eddy viscosity . The mixing length acts as a parameter which controls the turbulent part in . The main theoretical results that we have obtained concern the uniqueness of the solution for bounded eddy viscosities and small values of and its asymptotic...