A note on Weyl spectra of upper-triangular operator matrices

Abstract

Let M_C be a 2 x 2 upper triangular operator matrix acting on the Hilbert space H + K. In this paper, for given operators A and B, we give a new characterization of ∩_{C∈B(K,H) σ_w(M_C), whereσ_w(A) denote the Weyl spectrum of A.