This is a preview. Log in through your library . This monthly journal, begun in 1950, is devoted entirely to research in pure and applied mathematics, principally to the publication of original papers ...

Abstract. The spectra of the 2 × 2 upper triangular operator matrix M C =( A C 0 B ) acting on a Hilbert space 𝐻₁ ⨁ 𝐻₂ are investigated. We obtain a necessary and sufficient condition of 𝜎(𝑀𝐶) = ...