Numerical Ranges of Operators of Class C 0
Hari Bercovici · Linear and Multilinear Algebra · 2002
We show that the numerical range of an operator T of class C 0 is contained in the numerical range of the top block in its Jordan model. The operator contains this block as an orthogonal direct summand provided that the top block is finite dimensional, and one of the extreme points of its numerical range belongs to the numerical range of T.