English

A conservative de Branges-Rovnyak functional model for operator Schur functions on $\mathbb C^+$

Functional Analysis 2017-10-20 v3 Optimization and Control

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.

Keywords

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

R2 v1 2026-06-22T18:45:07.305Z