6 papers
Characteristic function of M. S. Livšic and triangular models of bounded linear operators
Vladimir K. Dubovoy, Bernd Kirstein, Conrad Mädler +1
This paper is dedicated to the introduction in a circle of ideas and methods, which are connected with the notion of characteristic function of a non-selfadjoint operator. We start…
Characteristic Function, Schur Parameters and Pseudocontinuation of Schur functions
Vladimir K. Dubovoy, Bernd Fritzsche, Bernd Kirstein +2
In [19] there is an approach to the investigation of the pseudocontinuability of Schur functions in terms of Schur parameters. In particular, there was obtained a criterion for the…
Characteristic Function, Schur Interpolation Problem and Darlington Synthesis
Sergey S. Boiko, Vladimir K. Dubovoy, Bernd Fritzsche +3
In this paper we would like to show the interrelation between the different mathematical theories concerning the Schur interpolation problem, contractions in Hilbert spaces, pseudo…
On special cases of Radon - Nikodym theorem for vector and operator valued measures
S. S. Boiko, V. K. Dubovoy, A. Y. Kheifets
We present a natural and simple proof of the Radon - Nikodym theorem for measures with values in the space of bounded linear operators on a separable Hilbert space. This space is n…
Description of Helson-Szegö measures in terms of the Schur parameter sequences of associated Schur functions
Vladimir K. Dubovoy, Bernd Fritzsche, Bernd Kirstein
Let mu be a probability measure on the Borelian sigma-algebra of the unit circle. Then we associate a Schur function theta in the unit disk with mu and give characterizations of th…
Shift Operators Contained in Contractions, Pseudocontinuable Schur Functions and Orthogonal Systems on the Unit Circle
Vladimir K. Dubovoy, Bernd Fritzsche, Bernd Kirstein
The main aim of this paper is to establish the connection between well-known criteria for the pseudocontinuability of a non-inner Schur function Theta in the unit disk. In a canoni…