Chapter 6: linear preservers on numerical ranges, numerical radii and unitary similarity invariant norms
Chi-Kwong Li, Nam‐Kiu Tsing · Linear and Multilinear Algebra · 1992
Many authors have studied linear preservers of different kinds of generalized numerical ranges and numerical radii. It is known that these operators are related to the linear isometrics of unitary similarity invariant norms. In this chapter we survey the results on these subjects.