On polynomial numerical hulls of normal matrices

Abstract

AbstractThe notion of polynomial numerical hull was introduced by O. Nevanlinna [Convergence of Iteration for linear equations, Birkhäuser, 1993]. In this note we determine the polynomial numerical hulls of matrices of the form A=A1⊕iA2, where A1,A2 are hermitian matrices. Also we study the relationship between rectangular hyperbolas and polynomial numerical hulls of order two for normal matrices. The polynomial numerical hulls of order two for some special matrices is studied