Let MX=（A C X B ）be a 2×2 operator matrix acting on the Hilbert space H＋K. For given A∈B（H）,B∈B（K）and C∈B（K,H）the set UX∈B（H,K）^σe（MX）is determined, whereσe（T）denotes the essential spectrum.
基金Foundation item： the National Natural Science Foundation of China （No. 10726043）.
文摘Let MX=（A C X B ）be a 2×2 operator matrix acting on the Hilbert space H＋K. For given A∈B（H）,B∈B（K）and C∈B（K,H）the set UX∈B（H,K）^σe（MX）is determined, whereσe（T）denotes the essential spectrum.
