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Norm-constrained determinantal representations of polynomials
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Norm-constrained determinantal representations of polynomials

Anatolii Grinshpan, Dmitry S Kaliuzhnyi-Verbovetskyi and Hugo J Woerdeman
10 Aug 2012
url
https://doi.org/10.48550/arxiv.1208.2288View
Preprint (Author's original)arXiv.org - Non-exclusive license to distribute Open

Abstract

Mathematics - Functional Analysis
For every multivariable polynomial $p$, with $p(0)=1$, we construct a determinantal representation $$p=\det (I - K Z),$$ where $Z$ is a diagonal matrix with coordinate variables on the diagonal and $K$ is a complex square matrix. Such a representation is equivalent to the existence of $K$ whose principal minors satisfy certain linear relations. When norm constraints on $K$ are imposed, we give connections to the multivariable von Neumann inequality, Agler denominators, and stability. We show that if a multivariable polynomial $q$, $q(0)=0,$ satisfies the von Neumann inequality, then $1-q$ admits a determinantal representation with $K$ a contraction. On the other hand, every determinantal representation with a contractive $K$ gives rise to a rational inner function in the Schur--Agler class.

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