Some Geometric Characteristics and Perturbations of Semi-Fredholm Operators

Snežana Č. Živković-Zlatanović

We consider some geometric characteristics of bounded operators on Banach spaces concerning the sets of upper and lower semi-Browder operators and left and right Browder operators. Using various operational quantities we give some perturbation results for upper and lower semi-Fredholm, Weyl and semi-Browder operators as well as for left and right Fredolm,Weyl and Browder operators.