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Wiener-Hopf indices of unimodular functions on the imaginary axis
A. E. Frazho, A. C. M. Ran, F. van Schagen
This paper is concerned with the Wiener-Hopf indices of unimodular rational matrix functions on the imaginary axis. These indices play a role in the Fredholm theory for Wiener-Hopf…
A Toeplitz-like operator with rational matrix symbol having poles on the unit circle: Invertibility and Riccati equations
G. J. Groenewald, S. ter Horst, J. Jaftha +1
This paper is a continuation of the work on unbounded Toeplitz-like operators $T_\Om$ with rational matrix symbol $\Om$ initiated in Groenewald et. al (Complex Anal. Oper. Theory 1…
Wiener-Hopf indices of unimodular functions on the unit circle, revisited
A. E. Frazho, M. A. Kaashoek, A. C. M. Ran +1
Inspired by the paper of Groenewald, Kaashoek and Ran (Wiener-Hopf indices of unitary functions on the unit circle in terms of realizations and related results on Toeplitz operator…
A Toeplitz-like operator with rational matrix symbol having poles on the unit circle: Fredholm characteristics
G. J. Groenewald, S. ter Horst, J. J. Jaftha +1
In a recent paper (Groenewald et al.\ {\em Complex Anal.\ Oper.\ Theory} \textbf{15:1} (2021)) we considered an unbounded Toeplitz-like operator generated by a rational matri…
An interlacing result for Hermitian matrices in Minkowski space
D. B. Janse van Rensburg, A. C. M. Ran, M. van Straaten
In this paper we will look at the well known interlacing problem, but here we consider the result for Hermitian matrices in the Minkowski space, an indefinite inner product space w…
A note on the structure of expansive matrices in indefinite inner product spaces
A. C. M. Ran
A result on the structure of expansive matrices in an indefinite inner product space is derived, which exhibits the largest unitary compression of the matrix.