On compressions of normal matrices (Q5957211)

This paper continues investigations of compressions and dilations of the numerical ranges \(W(A)\) of matrices by \textit{J. Maroulas} and \textit{M. Adam} [SIAM J. Matrix Anal. Appl. 21, No. 1, 230-244 (1999; Zbl 0943.15017)], paying special attention to normal matrices. A description of isometries \(P\) is given such that, for a normal matrix \(A\), the boundary \(\partial W(P^*AP)\) is tangential to \(\partial W(A)\) and some conditions for a ``satisfactory'' approximation are given.