Some Geometric Characteristics and Perturbations of Semi-Fredholm Operators

Abstract

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.