The intersection of left (right) spectra of 2 × 2 upper triangular operator matrices

When and are given, we denote by MC the operator matrix acting on the infinite-dimensional separable Hilbert space of the form In this paper, for given A and B, the sets and are determined, where and denote, respectively, the left spectrum of an operator T, the set of all the left invertible operators and the set of all the invertible operators from into .