Résumé:
When A∈ B (H) and B∈ B (K) are given, we denote by MC the operator on the Hilbert space H⊕ K of the form MC=(AC 0 B). In this paper we investigate the quasi-nilpotent part and the analytical core for the upper triangular operator matrix MC in terms of those of A and B. We give some necessary and sufficient conditions for MC to be left or right generalized Drazin invertible operator for some C∈ B (K, H). As an application, we study the existence and uniqueness of the solution for abstract boundary value problems described by upper triangular operator matrices with right generalized Drazin invertible component.