PERTURBATION OF FOUR KINDS OF POINT SPECTRUMS OF A CLASS OF UPPER TRIANGULAR OPERATOR MATRICES
Lan Zhang · Xitong kexue yu shuxue · 2010
The point spectrum is divided into four kindsσ_(p1),σ_(p2),σ_(p3)andσ_(p4).Inthis paper,let H and K be two separable Hilbert spaces.Donote by M_C the 2×2 uppertriangular operator matrix acting on HK of the form(OBAC).For given operators A∈B(H)and B∈B(K),the sets■C∈B(K,H)σ_(p1)(M_C),■C∈B(K,H)σ_(p2)(M_C),■C∈B(K,H)σ_(p3)(M_C)and■C∈B(K,H)σ_(p4)(M_C) are characterized.