Factorization theorem for -summing operators
We study some classes of summing operators between spaces of integrable functions with respect to a vector measure in order to prove a factorization theorem for -summing operators between Banach spaces.
Factorization through Inclusion Mappings between Ip-Spaces.
Factorizing multilinear operators on Banach spaces, C*-algebras and JB*-triples
In recent papers, the Right and the Strong* topologies have been introduced and studied on general Banach spaces. We characterize different types of continuity for multilinear operators (joint, uniform, etc.) with respect to the above topologies. We also study the relations between them. Finally, in the last section, we relate the joint Strong*-to-norm continuity of a multilinear operator T defined on C*-algebras (respectively, JB*-triples) to C*-summability (respectively, JB*-triple-summability)....
Failure of Nehari's theorem for multiplicative Hankel forms in Schatten classes
Ortega-Cerdà-Seip demonstrated that there are bounded multiplicative Hankel forms which do not arise from bounded symbols. On the other hand, when such a form is in the Hilbert-Schmidt class ₂, Helson showed that it has a bounded symbol. The present work investigates forms belonging to the Schatten classes between these two cases. It is shown that for every there exist multiplicative Hankel forms in the Schatten class which lack bounded symbols. The lower bound on p is in a certain sense optimal...
Fermeture des opérateurs dissipatifs invariants.
Fermi Golden Rule, Feshbach Method and embedded point spectrum
A method to study the embedded point spectrum of self-adjoint operators is described. The method combines the Mourre theory and the Limiting Absorption Principle with the Feshbach Projection Method. A more complete description of this method is contained in a joint paper with V. Jakić, where it is applied to a study of embedded point spectrum of Pauli-Fierz Hamiltonians.
Finite dimensional subspaces of
Finite dimensionality in socle of Banach algebras.
Finite propagation speed and kernels of strictly elliptic operators.
Finite rank commutators of Toeplitz operators on the bidisk
We study some algebraic properties of commutators of Toeplitz operators on the Hardy space of the bidisk. First, for two symbols where one is arbitrary and the other is (co-)analytic with respect to one fixed variable, we show that there is no nontrivial finite rank commutator. Also, for two symbols with separated variables, we prove that there is no nontrivial finite rank commutator or compact commutator in certain cases.
Finite rank intermediate Hankel operators and the big Hankel operator.
Finite representability and super-ideals of operators [Book]
Finite representability of the Yang operator.
Finite sections of truncated Toeplitz operators
We describe the C*-algebra associated with the finite sections discretization of truncated Toeplitz operators on the model space K2u where u is an infinite Blaschke product. As consequences, we get a stability criterion for the finite sections discretization and results on spectral and pseudospectral approximation.
Finite-dimensional subspaces of uniformly convex and uniformly smooth Banach lattices and trace classes
Finite-rank intermediate Hankel operators on the Bergman space.
Finite-rank perturbations of positive operators and isometries
We completely characterize the ranks of A - B and for operators A and B on a Hilbert space satisfying A ≥ B ≥ 0. Namely, let l and m be nonnegative integers or infinity. Then l = rank(A - B) and for some operators A and B with A ≥ B ≥ 0 on a Hilbert space of dimension n (1 ≤ n ≤ ∞) if and only if l = m = 0 or 0 < l ≤ m ≤ n. In particular, this answers in the negative the question posed by C. Benhida whether for positive operators A and B the finiteness of rank(A - B) implies that of . For...
First results on spectrally bounded operators
A linear mapping T from a subspace E of a Banach algebra into another Banach algebra is defined to be spectrally bounded if there is a constant M ≥ 0 such that r(Tx) ≤ Mr(x) for all x ∈ E, where r(·) denotes the spectral radius. We study some basic properties of this class of operators, which are sometimes analogous to, sometimes very different from, those of bounded operators between Banach spaces.
Fixed Point Theorems of the Banach and Krasnosel’skii Type for Mappings on -tuple Cartesian Product of Banach Algebras and Systems of Generalized Gripenberg’s Equations
In this paper we prove some fixed point theorems of the Banach and Krasnosel’skii type for mappings on the -tuple Cartesian product of a Banach algebra over . Using these theorems existence results for a system of integral equations of the Gripenberg’s type are proved. A sufficient condition for the nonexistence of blowing-up solutions of this system of integral equations is also proved.
Fixed points of semigroups of positive operators in KB-spaces