On the Ptak-Young generalization of the Schur-Cohn theorem

A new proof of the Ptak-Young generalization of the Schur-Cohn theorem is given, showing that the inertia of a certain generalized Bezoutian matrix determines the root distribution of a polynomial with respect to the unit disk. It is shown that the Ptak-Young theorem can also be formulated in terms of a Pick matrix. It is noted that the generalized Bezoutian is a structured matrix having a so-called generalized displacement structure.<
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