We will discuss the stability of isomorphisms on interpolation spaces constructed by the method of means. We focus on the methods determined by balanced sequences of quasi-concave functions and show that these methods have orbital description generated by an ideal of operators acting between couples of Banach spaces. We prove that if an operator is invertible in one orbit it is also invertible by nearby orbits.
Mieczyslaw Mastylo
Adam Mickiewicz University, Poznan