PERTURBATION OF POINT SPECTRA OF 2×2 UPPER TRIANGULAR OPERATOR MATRICES
Huang Junji · Xitong kexue yu shuxue · 2014
Perturbation of four kinds of point spectrum of 2×2 upper triangular operator matrices is studied.Based on the space decomposition technique and the subdivision of point spectrum and residual spectrum,a necessary and sufficient condition of σ_(pi)(M_C) = σ_(pi)(A) ∪σ_(pi)(B)(i = 1,2,3,4) for every bounded operator C is obtainedn by using its diagonal elements.