Resumen de Operational quantities derived from the norm and generalized Fredholm theory

Antonio Martinón Cejas , Manuel González Ortiz

• Several operational quantities, defined in terms of the norm and the class of finite dimensional Banach spaces, have been used to characterize the classes of upper and lower semi-Fredholm operators, strictly singular and strictly cosingular operators, and to derive some perturbation results.

  In this paper we shall introduce and study some operational quantities derived from the norm and associated to a space ideal. By means of these quantities we construct a generalized Fredholm theory in which the space ideal plays the role of the finite dimensional spaces, and we extend to this situation many of the results of the classical Fredholm theory