Linear operators
Measures of noncompactness in the study of solutions of nonlinear differential and integral equations
The aim of this paper is to make an overview of some existence results for nonlinear differential and integral equations. Those results were obtained by the author and his co-workers during last years with some help of the technique of measures of noncompactness and a fixed point theorem of Darbo type.
Moltiplicatori spettrali per l'operatore di Ornstein-Uhlenbeck
Questa è una rassegna di alcuni risultati recenti sui moltiplicatori spettrali dell'operatore di Ornstein-Uhlenbeck, un laplaciano naturale sullo spazio euclideo munito della misura gaussiana. I risultati sono inquadrati nell'ambito della teoria generale dei moltiplicatori spettrali per laplaciani generalizzati.
Narrow operators (a survey)
Narrow operators are those operators defined on function spaces which are "small" at signs, i.e., at {-1,0,1}-valued functions. We summarize here some results and problems on them. One of the most interesting things is that if E has an unconditional basis then each operator on E is a sum of two narrow operators, while the sum of two narrow operators on L₁ is narrow. Recently this notion was generalized to vector lattices. This generalization explained the phenomena of sums: the set of all regular...
Nonexpansive mappings and iterative methods in uniformly convex Banach spaces.
On positive operator-valued continuous maps
In the paper the geometric properties of the positive cone and positive part of the unit ball of the space of operator-valued continuous space are discussed. In particular we show that
On quantum informational thermodynamics with macrostates defined with respect to several operators [Book]
On the reflexivity of multigenerator algebras [Book]
Ostrowski's type inequalities for continuous functions of selfadjoint operators on Hilbert spaces: a survey of recent results.
Positivity in the theory of supercyclic operators
A bounded linear operator T defined on a Banach space X is said to be supercyclic if there exists a vector x ∈ X such that the projective orbit {λTⁿx : λ ∈ ℂ, n ∈ ℕ} is dense in X. The aim of this survey is to show the relationship between positivity and supercyclicity. This relationship comes from the so called Positive Supercyclicity Theorem. Throughout this exposition, interesting new directions and open problems will appear.
Recent developments in hypercyclicity.
In these notes we report on recent progress in the theory of hypercyclic and chaotic operators. Our discussion will be guided by the following fundamental problems: How do we recognize hypercyclic operators? How many vectors are hypercyclic? How many operators are hypercyclic? How big can non-dense orbits be?
Recent progress and open questions on the numerical index of Banach spaces.
The aim of this paper is to review the state-of-the-art of recent research concerning the numerical index of Banach spaces, by presenting some of the results found in the last years and proposing a number of related open problems.
Recent progress in the theory of absolutely p-summing operators
Some generalizations of Kadison's theorem: a survey.
Motivated by a well-known result of Kadison that describes surjective isometries of the space of compact and the space of bounded operators on a Hilbert space, in this paper we investigate the structure of surjective isometries on the space of compact and on the space of bounded operators between Banach spaces. We give an example to show that isometries in general need not be of the canonical form. As an application of our study of the group of isometries, we consider the algebraic reflexivity of...
Some summation formulae in commutative Leibniz algebras with logarithms
Special operators on classical spaces of analytic functions.
Spectral analysis and synthesis
Square functions, bounded analytic semigroups, and applications
To any bounded analytic semigroup on Hilbert space or on -space, one may associate natural ’square functions’. In this survey paper, we review old and recent results on these square functions, as well as some extensions to various classes of Banach spaces, including noncommutative -spaces, Banach lattices, and their subspaces. We give some applications to functional calculus, similarity problems, multiplier theory, and control theory.
Stability of operator semigroups: ideas and results
The Positive Supercyclicity Theorem.
We present some recent results related with supercyclic operators, also some of its consequences. We will finalize with new related questions.