Browder spectra for upper triangular operator matrices

When A∈B(H)A∈B(H) and B∈B(K)B∈B(K) are given, we denote by MCMC the operator acting on the infinite dimensional separable Hilbert space H⊕KH⊕K of the form MC=(AC0B). In this paper, we prove that⋂C∈B(K,H)σb(MC)=σab(A)∪σab(B∗)∪{λ∈C:n(A−λI)+n(B−λI)≠d(A−λI)+d(B−λI)}, where σb(T)σb(T), σab(T)σab(T), n(T)n(T), d(T)d(T) and T∗T∗ denote the Browder spectrum, Browder essential approximate point spectrum, nullity, deficiency and conjugate of T, respectively. Some related results are obtained.