J-Unitary Factorization and the Schur Algorithm for Nevanlinna Functions in an Indefinite Setting
We introduce a Schur transformation for generalized Nevanlinna functions and show that it can be used in obtaining the unique minimal factorization of a class of rational Jℓ-unitary 2 × 2 matrix functions into elementary factors from the same class.
D. Alpay, A. Dijksma and H. Langer, J-unitary factorization and the Schur algorithm for Nevanlinna functions in an indefinite setting. Linear algebra and applications, vol. 419 (2006) 675-709.