On the perturbation theory for Fredholm operators
This work is concerned with perturbation theory for Fredholm operators. In the classical theory of linear Fredholm operators a fundamental role is played by compact operators. In fact, a condition for an operator to be Fredholm is given in terms of compact operators, and it is known that the class of Fredholm operators is invariant under compact perturbations. The aim of this paper is to generalize these results introducing a new class of operators (l-set-contractive, demicompact and others) containing the class of compact operators.
perturbation theory for Fredholm operators
scientific article; zbMATH DE number 3886595