Spectral Sets: Numerical Range and Beyond

Michel Crouzeix, Anne Greenbaum

We extend the proof in [M.~Crouzeix and C.~Palencia, {\em The numerical range is a $(1+\sqrt{2})$-spectral set}, SIAM Jour.~Matrix Anal.~Appl., 38 (2017), pp.~649-655] to show th…