Corners of Numerical Ranges
Heinz Langer, Alexander Markus, Christiane Tretter · Birkhäuser Basel eBooks · 2001
It is well-known that a corner of the numerical range of a bounded linear operator T in a Hilbert space belongs to the spectrum σ( T ). In this paper we prove corresponding results for the corners of the numerical range of an analytic operator function and of the quadratic numerical range of a 2 × 2 block operator matrix. These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.