Some results of fredholm perturbations of multivalued linear operator in normed spaces
Aymen Ammar, Aicha Ezzadam, Aref Jeribi · Filomat · 2023
In the present paper, we establish first the relation between the perturbation of upper Fredholm and strictly singular, and then the relation between lower semi-Fredholm and strictly cosingular linear relations. Most importantly in Theorem 3.4, we show that P(F?(X,Y)) coincides with SC(X,Y).We bring to light, the relationship between the essential spectra of a multivalued linear operator and its selection