J-spectral factorization and equalizing vectors

O.V. Iftime, H.J. Zwart

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    For the Wiener class of matrix-valued functions we provide necessary and sufficient conditions for the existence of a $J$-spectral factorization. One of these conditions is in terms of equalizing vectors. A second one states that the existence of a $J$-spectral factorization is equivalent to the invertibility of the Toeplitz operator associated to the matrix to be factorized. Our proofs are simple and only use standard results of general factorization theory. Note that we do not use a state space representation of the system. However, we make the connection with the known results for the Pritchard-Salamon class of systems where an equivalent condition with the solvability of an algebraic Riccati equation is given. For Riesz-spectral systems another necessary and sufficient conditions for the existence of a $J$-spectral factorization in terms of the Hamiltonian is added.
    Original languageEnglish
    Place of PublicationEnschede
    PublisherUniversity of Twente, Department of Applied Mathematics
    Number of pages15
    Publication statusPublished - 2000

    Publication series

    PublisherDepartment of Applied Mathematics, University of Twente
    ISSN (Print)0169-2690


    • MSC-93B36
    • MSC-93C25
    • IR-65732
    • MSC-47B35
    • EWI-3365
    • MSC-47A68


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