Produits tensoriels complétés d'espaces de Hilbert
Produits tensoriels d'espaces de Banach et classes d'applications linéaires
Produits tensoriels et , applications -sommantes, applications -radonifiantes
Projections onto the spaces of Toeplitz operators
Projections onto the spaces of all Toeplitz operators on the N-torus and the unit sphere are constructed. The constructions are also extended to generalized Toeplitz operators and applied to show hyperreflexivity results.
Prolongement d’un opérateur d’un sous-espace de dans
Prolongements maximaux positifs d'opérateurs positifs et problèmes de perturbations singulières
Proper contractions and invariant subspaces.
Properties of derivations on some convolution algebras
For all convolution algebras L 1[0, 1); L loc1 and A(ω) = ∩n L 1(ωn), the derivations are of the form D μ f = Xf * μ for suitable measures μ, where (Xf)(t) = tf(t). We describe the (weakly) compact as well as the (weakly) Montel derivations on these algebras in terms of properties of the measure μ. Moreover, for all these algebras we show that the extension of D μ to a natural dual space is weak-star continuous.
Properties of the slant weighted Toeplitz operator.
Properties of two variables Toeplitz type operators
The investigation of properties of generalized Toeplitz operators with respect to the pairs of doubly commuting contractions (the abstract analogue of classical two variable Toeplitz operators) is proceeded. We especially concentrate on the condition of existence such a non-zero operator. There are also presented conditions of analyticity of such an operator.
Pseudo shift operators with large images
We give suitable conditions for the existence of many holomorphic functions f on a disc such that the image of any nonempty open subset under the action of pseudo shift operators on f is arbitrarily large. This generalizes an earlier result about images of derivatives and completes another one on infinite order differential operators.
Pseudocomplémentation dans les espaces de Banach
This paper introduces the following definition: a closed subspace Z of a Banach space E is pseudocomplemented in E if for every linear continuous operator u from Z to Z there is a linear continuous extension ū of u from E to E. For instance, every subspace complemented in E is pseudocomplemented in E. First, the pseudocomplemented hilbertian subspaces of are characterized and, in with p in [1, + ∞[, classes of closed subspaces in which the notions of complementation and pseudocomplementation...
p-trivial Banach spaces
Puissances d'un opérateur régularisant
Putnam-Fuglede theorem and the range-kernel orthogonality of derivations.
q-deformed circularity for an unbounded operator in Hilbert space
The notion of strong circularity for an unbounded operator is introduced and studied. Moreover, q-deformed circularity as a q-analogue of circularity is characterized in terms of the partially isometric and the positive parts of the polar decomposition.
Quadratic functionals on modules over complex Banach *-algebras with an approximate identity
The problem of representability of quadratic functionals by sesquilinear forms is studied in this article in the setting of a module over an algebra that belongs to a certain class of complex Banach *-algebras with an approximate identity. That class includes C*-algebras as well as H*-algebras and their trace classes. Each quadratic functional acting on such a module can be represented by a unique sesquilinear form. That form generally takes values in a larger algebra than the given quadratic functional...
Quand est-ce que des bornes de Hardy permettent de calculer une constante de Poincaré exacte sur la droite ?
Classically, Hardy’s inequality enables to estimate the spectral gap of a one-dimensional diffusion up to a factor belonging to . The goal of this paper is to better understand the latter factor, at least in a symmetric setting. In particular, we will give an asymptotical criterion implying that its value is exactly 4. The underlying argument is based on a semi-explicit functional for the spectral gap, which is monotone in some rearrangement of the data. To find it will resort to some regularity...
Quantification of the reciprocal Dunford-Pettis property
We prove in particular that Banach spaces of the form C₀(Ω), where Ω is a locally compact space, enjoy a quantitative version of the reciprocal Dunford-Pettis property.
Quasiaffine transforms of operators
We obtain a new sufficient condition (which may be useful elsewhere) that a compact perturbation of a normal operator be the quasiaffine transform of some normal operator. We also give some applications of this result.