Integration with respect to the canonical spectral measure in sequence spaces.
Intertwining operators
Introduction aux méthodes euclidiennes en théorie quantique des champs
Invertibility of the commutator of an element in a C*-algebra and its Moore-Penrose inverse
We study the subset in a unital C*-algebra composed of elements a such that is invertible, where denotes the Moore-Penrose inverse of a. A distinguished subset of this set is also investigated. Furthermore we study sequences of elements belonging to the aforementioned subsets.
Isometries of Musielak-Orlicz spaces II
A characterization of isometries of complex Musielak-Orlicz spaces is given. If is not a Hilbert space and is a surjective isometry, then there exist a regular set isomorphism τ from (T,Σ,μ) onto itself and a measurable function w such that U(f) = w ·(f ∘ τ) for all . Isometries of real Nakano spaces, a particular case of Musielak-Orlicz spaces, are also studied.
Isometries of Orlicz Spaces of Vector Valued Functions.
Iterative solution of eigenvalue problems for normal operators
We will discuss Kellogg's iterations in eigenvalue problems for normal operators. A certain generalisation of the convergence theorem is shown.
Jensen's Inequality for Operators and Löwner 's Theorem.
J-majorizing and modular operators in J-spaces
Joint essential spectra
Joint spectra
La Extension De Caratheodory Para Medidas Con Valores En Operadores Positivos.
Lie algebras generated by Jordan operators
It is proved that if is a Jordan operator on a Hilbert space with the Jordan decomposition , where is normal and is compact and quasinilpotent, i = 1,2, and the Lie algebra generated by J₁,J₂ is an Engel Lie algebra, then the Banach algebra generated by J₁,J₂ is an Engel algebra. Some results for normal operators and Jordan operators on Banach spaces are given.
Limacons, normal operators and polar factorizations.
Local spectrum and Kaplansky's theorem on algebraic operators
Using elementary arguments we improve former results of P. Vrbová concerning local spectrum. As a consequence, we obtain a new proof of Kaplansky’s theorem on algebraic operators on a Banach space.
Logarithmic concavity, unitarity and selfadjointness
Isometric automorphisms of normed linear spaces are characterized by suitable concavity properties of powers of operators. Bounded selfadjoint operators in Hilbert spaces are described by parallel concavity properties of the exponential group. Unbounded infinitesimal generators of 𝓒₀-groups of Hilbert space operators having concavity properties are characterized as well.
Matrix order in Bohr inequality for operators.
Means and Concave Products of Positive Semi-Definite Matrices.
Means and convex combinations of unitary operators.
Means of Positive Linear Operators.