A general separation theorem for mappings, saddle-points duality and conjugate functions
A survey of some recent inequalities for the norm and numerical radius of operators in Hilbert spaces.
An Exposition of the Connection between Limit-Periodic Potentials and Profinite Groups
We classify the hulls of different limit-periodic potentials and show that the hull of a limit-periodic potential is a procyclic group. We describe how limit-periodic potentials can be generated from a procyclic group and answer arising questions. As an expository paper, we discuss the connection between limit-periodic potentials and profinite groups as completely as possible and review some recent results on Schrödinger operators obtained in this...
An introduction to Rota’s universal operators: properties, old and new examples and future issues
The Invariant Subspace Problem for Hilbert spaces is a long-standing question and the use of universal operators in the sense of Rota has been an important tool for studying such important problem. In this survey, we focus on Rota’s universal operators, pointing out their main properties and exhibiting some old and recent examples.
An operator-theoretic approach to truncated moment problems
We survey recent developments in operator theory and moment problems, beginning with the study of quadratic hyponormality for unilateral weighted shifts, its connections with truncated Hamburger, Stieltjes, Hausdorff and Toeplitz moment problems, and the subsequent proof that polynomially hyponormal operators need not be subnormal. We present a general elementary approach to truncated moment problems in one or several real or complex variables, based on matrix positivity and extension. Together...
Asymptotic behaviour of semigroups of operators
Calcul pseudodifférentiel -adique
Combinatorial approach to Baker-Campbell-Hausdorff exponents
Composition operators in the Dirichlet series setting
In this work, we begin with a survey of composition operators on the Hardy space H² and on the Wiener algebra A⁺ of absolutely convergent Taylor series, with special emphasis on their compactness, or invertibility, or isometric character. The main results are due respectively to J. Shapiro and D.~Newman. In a second part, we present more recent results, due to Gordon and Hedenmalm on the one hand, and to Bayart, the author et al. on the other hand, concerning the analogues of H² and A⁺ in the setting...
Dilations of Hilbert space operators (General theory) [Book]
Dual algebras generated by von Neumann n-tuples over strictly pseudoconvex sets [Book]
Dual Banach algebras and Connes-amenability.
Dynamics of properties of Toeplitz operators on weighted Bergman spaces.
Einige Aspekte der Funktionalanalysis.
Fixed point and continuation results for contractions in metric and gauge spaces
We present an overview of generalizations of Banach's fixed point theorem and continuation results for contractions, i.e., results establishing that the existence of a fixed point is preserved by suitable homotopies. We will consider single-valued and multi-valued contractions in metric and in gauge spaces.
Fredholm determinants
The article provides with a down to earth exposition of the Fredholm theory with applications to Brownian motion and KdV equation.
Fredholm, Riesz and local spectral theory of multipliers.
Higher order differentiability of nonlinear operators on normed spaces. II.
La figura espectral del producto tensorial de dos operadores.
Sea H un espacio de Hilbert complejo, separable y de dimensión infinita. Denotaremos por L(H) al álgebra de todos los operadores acotados en H. Carl Pearcy en 1977 introdujo el concepto de figura espectral de un operador T en L(H) [13]. Sin lugar a dudas hay dos resultados que hacen de la figura espectral de un operador un concepto importante. El primero se debe a Brown, Douglas y Fillmore:"Dos operadores esencialmente normales son débilmente equivalentes si y sólo si tienen la misma figura espectral".El...
Le equazioni funzionali in analisi non lineare