Spectral inclusion by the quadratic numerical range of 2 x 2 operator matrices with unbounded entries
Jie Liu, Junjie Huang, Alatancang Chen · Filomat · 2020
This paper deals with the spectral inclusion properties of 2 x 2 operator matrices with unbounded entries in Hilbert space. The conditions for spectral inclusion by the quadratic numerical range are described. In addition, some examples are given to illustrate the main results.