Let be a compatible pair of Banach spaces and let be an operator that acts boundedly on both and . Let be the corresponding operator on the complex interpolation space . The aim of this paper is to study the spectral properties of . We show that in general the set-valued function is discontinuous even in inner points and show that each operator satisfies the local uniqueness-of-resolvent condition of Ransford. Further we study connections with the real interpolation method. |