A conservative de Branges-Rovnyak functional model for operator Schur functions on $\mathbb C^+$
Abstract
We present a solution of the operator-valued Schur-function realization problem on the right-half plane by developing the corresponding de Branges-Rovnyak canonical conservative simple functional model. This model corresponds to the closely connected unitary model in the disk setting, but we work the theory out directly in the right-half plane, which allows us to exhibit structure which is absent in the disk case. A main feature of the study is that the connecting operator is unbounded, and so we need to make use of the theory of well-posed continuous-time systems. In order to strengthen the classical uniqueness result (which states uniqueness up to unitary similarity), we introduce non-invertible intertwinements of system nodes.
Cite
@article{arxiv.1703.04705,
title = {A conservative de Branges-Rovnyak functional model for operator Schur functions on $\mathbb C^+$},
author = {Joseph A. Ball and Mikael Kurula and Olof J. Staffans},
journal= {arXiv preprint arXiv:1703.04705},
year = {2017}
}
Comments
To appear in Complex Analysis and Operator Theory