3 papers
math.FA2026
The classes of bivariate Schur and Herglotz matrix-valued rational functions: realizations, symmetrizations, and related determinantal representations
Radomił Baran, Piotr Pikul, Hugo J. Woerdeman +1
We present a finite-dimensional realization theory for bivariate rational functions that are contractive or have nonnegative real part on the bidisc or on the bihalfplane. We show…
math.FA2026
Symmetric Schur-class functions on the bidisk and Schur-class functions on the symmetrized bidisk
Radomił Baran, Hugo J. Woerdeman
We present some thoughts on the relation between symmetric Schur-class functions on the bidisk and Schur-class functions on the symmetrized bidisk. Among other things, use of this…
math.FA2025
Contractive realization theory for the annulus and other intersections of discs on the Riemann sphere
Radomił Baran, Piotr Pikul, Hugo J. Woerdeman +1
We develop contractive finite dimensional realizations for rational matrix functions of one variable on domains that are not simply connected, such as the annulus. The proof uses m…