Let H and K be complex infinite dimensional separable Hilbert spaces. We denote by MC = pmatrix A C \\ 0 B pmatrix a 2 ×2 upper triangular operator matrix acting on H ⊕ K, where A ∈ B (H), B ∈ B (K) and C ∈ B (K, H). In this paper, we mainly characterize the equivalent conditions for the 2 × 2 upper triangular operator matrices such that they satisfyWeyl’s theorem using the features of the elements on the diagonal.
Sun et al. (Wed,) studied this question.