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Spectral subspaces and non-commutative Hilbert transforms

Narcisse Randrianantoanina (2002)

Colloquium Mathematicae

Let G be a locally compact abelian group and ℳ be a semifinite von Neumann algebra with a faithful semifinite normal trace τ. We study Hilbert transforms associated with G-flows on ℳ and closed semigroups Σ of Ĝ satisfying the condition Σ ∪ (-Σ) = Ĝ. We prove that Hilbert transforms on such closed semigroups satisfy a weak-type estimate and can be extended as linear maps from L¹(ℳ,τ) into L 1 , ( , τ ) . As an application, we obtain a Matsaev-type result for p = 1: if x is a quasi-nilpotent compact operator...

Spectre du noyau intégral ( x 2 + y 2 + 1 ) - 1

Michel Gaudin (1981)

Annales de l'institut Fourier

On construit les fonctions propres sur R et les valeurs caractéristiques λ n du noyau de Hilbert-Schmidt ( x 2 + y 2 + 1 ) - 1 . Le spectre est donné par la solution d’une équation transcendante dont le comportement asymptotique est λ n 1 2 exp ( π n ) .

Strichartz inequality for orthonormal functions

Rupert Frank, Mathieu Lewin, Elliott H. Lieb, Robert Seiringer (2014)

Journal of the European Mathematical Society

We prove a Strichartz inequality for a system of orthonormal functions, with an optimal behavior of the constant in the limit of a large number of functions. The estimate generalizes the usual Strichartz inequality, in the same fashion as the Lieb-Thirring inequality generalizes the Sobolev inequality. As an application, we consider the Schrödinger equation in a time-dependent potential and we show the existence of the wave operator in Schatten spaces.

Subalgebras to a Wiener type algebra of pseudo-differential operators

Joachim Toft (2001)

Annales de l’institut Fourier

We study general continuity properties for an increasing family of Banach spaces S w p of classes for pseudo-differential symbols, where S w = S w was introduced by J. Sjöstrand in 1993. We prove that the operators in Op ( S w p ) are Schatten-von Neumann operators of order p on L 2 . We prove also that Op ( S w p ) Op ( S w r ) Op ( S w r ) and S w p · S w q S w r , provided 1 / p + 1 / q = 1 / r . If instead 1 / p + 1 / q = 1 + 1 / r , then S w p w * S w q S w r . By modifying the definition of the S w p -spaces, one also obtains symbol classes related to the S ( m , g ) spaces.

Sur quelques extensions au cadre banachique de la notion d'opérateur de Hilbert-Schmidt

Said Amana Abdillah, Jean Esterle, Bernhard H. Haak (2015)

Studia Mathematica

In this work we discuss several ways to extend to the context of Banach spaces the notion of Hilbert-Schmidt operator: p-summing operators, γ-summing or γ-radonifying operators, weakly* 1-nuclear operators and classes of operators defined via factorization properties. We introduce the class PS₂(E;F) of pre-Hilbert-Schmidt operators as the class of all operators u: E → F such that w ∘ u ∘ v is Hilbert-Schmidt for every bounded operator v: H₁ → E and every bounded operator w: F → H₂, where H₁ and...

Currently displaying 361 – 380 of 501