Generalized Drazin-type spectra of Operator matrices.
Author
Tajmouati, A.
Abkari, M.
Karmouni, M.
Abstract
In this paper, we investigate the limit points set of surjective and approximate point spectra of upper triangular operator matrices . We prove that σ*(MC) ∪ W=σ*(A)∪ σ*(B) where W is the union of certain holes in σ*(MC), which happen to be subsets of σ lgD(B) ∩ σrgD(A), σ* ∈ {σlgD, σrgD} are the limit points set of surjective and approximate point spectra. Furthermore, several sufficient conditions for σ* (MC) = σ* (A)∪σ* (B) holds for every C ∈ ℬ(Y,X) are given.