Browder essential approximate point spectra and hypercyclicity for operator matrices

Semi-browder Essential Spectra of Quasisimilar Operators

If T and S are quasisimilar bounded operators on Banach spaces, we prove that each closed-and-open subset of the lower semiBrowder essential spectrum of T intersects one special part of the upper semi-Browder essential spectra of T and S. AMS Mathematics Subject Classification (1991): 47A53, 47A10

Upper Triangular Operator Matrices , SVEP and Browder , Weyl Theorems

A Banach space operator T ∈ B(X ) is polaroid if points λ ∈ isoσσ(T ) are poles of the resolvent of T . Let σa(T ), σw(T ), σaw(T ), σSF+(T ) and σSF−(T ) denote, respectively, the approximate point, the Weyl, the Weyl essential approximate, the upper semi–Fredholm and lower semi–Fredholm spectrum of T . For A, B and C ∈ B(X ), let MC denote the operator matrix (

Joint Browder Spectra and Tensor Products

Approximate fixed point theorems for Geraghty-contractions

The purpose of this paper is to obtain necessary and suffcient conditionsfor existence approximate fixed point on Geraghty-contraction. In this paper,denitions of approximate -pair fixed point for two maps Tα , Sα and theirdiameters are given in a metric space.

Approximate Factorization Constraint Preconditioners for Saddle-Point Matrices

We consider the application of the conjugate gradient method to the solution of large, symmetric indefinite linear systems. Special emphasis is put on the use of constraint preconditioners and a new factorization that can reduce the number of flops required by the preconditioning step. Results concerning the eigenvalues of the preconditioned matrix and its minimum polynomial are given. Numerica...