Perturbations by Quadratic Forms and Invariance of Essential Spectra.
Perturbations of operators satisfying a local growth condition.
Perturbations of real parts of eigenvalues of bounded linear operators in a Hilbert space
Let be a bounded linear operator in a complex separable Hilbert space , and be a selfadjoint operator in . Assuming that belongs to the Schatten-von Neumann ideal
Perturbations of Selfadjoint Operators with Point Spectra by Restrictions and Selfadjoint Extensions.
Polaroid type operators and compact perturbations
A bounded linear operator T acting on a Hilbert space is said to be polaroid if each isolated point in the spectrum is a pole of the resolvent of T. There are several generalizations of the polaroid property. We investigate compact perturbations of polaroid type operators. We prove that, given an operator T and ε > 0, there exists a compact operator K with ||K|| < ε such that T + K is polaroid. Moreover, we characterize those operators for which a certain polaroid type property is stable under...
Polaroid type operators under perturbations
A bounded operator T defined on a Banach space is said to be polaroid if every isolated point of the spectrum is a pole of the resolvent. The "polaroid" condition is related to the conditions of being left polaroid, right polaroid, or a-polaroid. In this paper we explore all these conditions under commuting perturbations K. As a consequence, we give a general framework from which we obtain, and also extend, recent results concerning Weyl type theorems (generalized or not) for T + K, where K is an...
Polynomials in the Volterra and Ritt operators
We continue the paper [Ts] on the boundedness of polynomials in the Volterra operator. This provides new ways of constructing power-bounded operators. It seems interesting to point out that a similar procedure applies to the operators satisfying the Ritt resolvent condition: compare Theorem 5 and Theorem 9 below.
Positive Operators and Elliptic Eigenvalue Problems.
Positivity and stability for a system of transport equations with unbounded boundary perturbations.
Positivity Improving Operators and Hypercontractivity.
Power-bounded elements and radical Banach algebras
Firstly, we give extensions of results of Gelfand, Esterle and Katznelson--Tzafriri on power-bounded operators. Secondly, some results and questions relating to power-bounded elements in the unitization of a commutative radical Banach algebra are discussed.
Powers of operators
Preassigning eigenvalues and zeros of nuclear operators
Precompactness in the uniform ergodic theory
We characterize the Banach space operators T whose arithmetic means form a precompact set in the operator norm topology. This occurs if and only if the sequence is precompact and the point 1 is at most a simple pole of the resolvent of T. Equivalent geometric conditions are also obtained.
Problème des moments matriciels sur la droite : construction d'une famille de solutions et questions d'unicité
Problems on Banach spaces
Projection methods in the approximate solution of the eigenvalue problem in a Hilbert space
Projection Seminorms and the Field of Values of Linear Operators.
Property (gz) for bounded linear operators
Proprietà spettrali di certi operatori lineari non compatti