A quasinilpotent operator with reflexive commutant
An example of a nonzero quasinilpotent operator with reflexive commutant is presented.
A quasi-nilpotent operator with reflexive commutant, II
A new example of a non-zero quasi-nilpotent operator T with reflexive commutant is presented. The norms converge to zero arbitrarily fast.
A -range and φ- spatial Numerical range of a Tensor
A ratio ergodic theorem for multiparameter non-singular actions
We prove a ratio ergodic theorem for non-singular free and actions, along balls in an arbitrary norm. Using a Chacon–Ornstein type lemma the proof is reduced to a statement about the amount of mass of a probability measure that can concentrate on (thickened) boundaries of balls in . The proof relies on geometric properties of norms, including the Besicovitch covering lemma and the fact that boundaries of balls have lower dimension than the ambient space. We also show that for general group...
A relation between the multiplicity of the second eigenvalue of a graph Laplacian, Courant's nodal line theorem and the substantial dimension of tight polyhedral surfaces.
A relation to Hilbert's integral inequality and some base Hilbert-type inequalities.
A remark concerning uniqueness of the Wold decomposition of finite-dimensional stationary processes.
The uniqueness of the Wold decomposition of a finite-dimensional stationary process without assumption of full rank stationary process and the Lebesgue decomposition of its spectral measure is easily obtained.
A remark on Fefferman-Stein's inequalities.
It is proved that, for some reverse doubling weight functions, the related operator which appears in the Fefferman Stein's inequality can be taken smaller than those operators for which such an inequality is known to be true.
A Remark on Perturbations of Compact Operators.
A remark on the d-characteristic and the -characteristic of linear operators in a Banach space
A remark on the range of elementary operators
Let denote the algebra of all bounded linear operators on a separable infinite dimensional complex Hilbert space into itself. Given , we define the elementary operator by . In this paper we study the class of operators which have the following property: implies for all trace class operators . Such operators are termed generalized quasi-adjoints. The main result is the equivalence between this character and the fact that the ultraweak closure of the range of is closed under taking...
A remark on the weighted averages for superadditive processes.
A Remark on Two Hilbert Space Scattering Theory.
A representation theorem for operators on a space of interval functions.
A resolvent condition implying power boundedness
The Ritt and Kreiss resolvent conditions are related to the behaviour of the powers and their various means. In particular, it is shown that the Ritt condition implies the power boundedness. This improves the Nevanlinna characterization of the sublinear decay of the differences of the consecutive powers in the Esterle-Katznelson-Tzafriri theorem, and actually characterizes the analytic Ritt condition by two geometric properties of the powers.
A Riccati equation arising in a boundary control problem for distributed parameters
Si prova resistenza locale della soluzione di una equazione di Riccati che si incontra in un problema di controllo ottimale. In ipotesi di regolarità per il costo si prova resistenza globale. Il problema astratto considerato è il modello di alcuni problemi di controllo ottimale governati da equazioni paraboliche con controllo sulla frontiera.
A rigorous approach to relativistic corrections of bound state energies for spin-1/2 particles
A scattering theory for automorphic functions
A semigroup analogue of the Fonf-Lin-Wojtaszczyk ergodic characterization of reflexive Banach spaces with a basis
In analogy to a recent result by V. Fonf, M. Lin, and P. Wojtaszczyk, we prove the following characterizations of a Banach space X with a basis. (i) X is finite-dimensional if and only if every bounded, uniformly continuous, mean ergodic semigroup on X is uniformly mean ergodic. (ii) X is reflexive if and only if every bounded strongly continuous semigroup is mean ergodic if and only if every bounded uniformly continuous semigroup on X is mean ergodic.
A Short Proof of Radjavi's Theorem on Self-Commutators.