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Perfect Copositive Matrices

In this paper we give a first study of perfect copositive $n \times n$ matrices. They can be used to find rational certificates for completely positive matrices. We describe similarities and differences to classical perfect, positive definite matrices. Most of the differences occur only for $n \geq...

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Bibliographic Details
Published in:Communications in Mathematics 2023-07, Vol.31 (2023), Issue 2...
Main Authors: Dannenberg, Valentin, Schürmann, Achill
Format: Article
Language:English
Online Access:Get full text
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Summary:In this paper we give a first study of perfect copositive $n \times n$ matrices. They can be used to find rational certificates for completely positive matrices. We describe similarities and differences to classical perfect, positive definite matrices. Most of the differences occur only for $n \geq 3$, where we find for instance lower rank and indefinite perfect matrices. Nevertheless, we find for all $n$ that for every classical perfect matrix there is an arithmetically equivalent one which is also perfect copositive. Furthermore we study the neighborhood graph and polyhedral structure of perfect copositive matrices. As an application we obtain a new characterization of the cone of completely positive matrices: It is equal to the set of nonnegative matrices having a nonnegative inner product with all perfect copositive matrices.
ISSN:2336-1298
2336-1298
DOI:10.46298/cm.11141