The spectral equality for upper triangular operator matrices with unbounded entries
D yu Wu, Alatancang Chen, Tin-Yau Tam · Operators and Matrices · 2017
be a 2 × 2 unbounded upper triangular operator matrix on the complex Hilbert space X × X .We investigate the conditions under which σ. Some necessary and sufficient conditions are obtained.The results generalize some results of Han, Du, and Barraa in the bounded case.