Perturbation of the Defect Spectrum of 3×3 Upper Triangular Operator Matrices
Lan Zhang · Journal of Inner Mongolia University · 2013
Let H 1,H 2 and H 3 be separable Hilbert spaces,A ∈ B(H 1),B ∈ B(H 2) and C ∈ B(H 3) are given,operator matrices M(X,Y,Z) = (A X Y 0 B Z 0 0 C) are defined.The perturbation of the defect spectum and the approximate point spectrum of M(X,Y,Z) is characterized.