Generalized Derivations and Norm Equality in Normed Ideals

2000 Mathematics Subject Classification: 47A10, 47A12, 47A30, 47B10, 47B20, 47B37, 47B47, 47D50.We compare the norm of a generalized derivation on a Hilbert space with the norm of its restrictions to Schatten norm ideals

On the Product of Two Generalized Derivations

Two elements A and B in a ring R determine a generalized derivation deltaA,B on R by setting δA,B(X) = AX - XA for any X in R. We characterize when the product δC,DδA,B is a generalized derivation in the cases when the ring R is the algebra of all bounded operators on a Banach space epsilon, and when R is a C*-algebra U. We use the se characterizations to compute the commutant of the range of δA,B

Le treillis des sous-espaces hyperinvariants d'un operateur nilpotent sur un espace de Banach

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

On the perturbations of spectra of upper triangular operator matrices

AbstractIn this paper we investigate perturbations of the regular spectrum of an upper triangular operator matrix such as MC=[AC0B] acting on a Hilbert space H⊕K