We prove a general Borg-type result for reflectionless unitary
Cantero-Moral-Velazquez (CMV) operators U associated with orthogonal
polynomials on the unit circle. The spectrum of U is assumed to be a connected
arc on the unit circle. This extends a recent result of Simon in connection
with a periodic CMV operator with spectrum the whole unit circle.
In the course of deriving the Borg-type result we also use exponential
Herglotz representations of Caratheodory functions to prove an infinite
sequence of trace formulas connected with the CMV operator U.
@article{0501212,
author = {Gesztesy, Fritz and Zinchenko, Maxim},
title = {A Borg-Type Theorem Associated with Orthogonal Polynomials on the Unit
Circle},
journal = {arXiv},
volume = {2005},
number = {0},
year = {2005},
language = {en},
url = {http://dml.mathdoc.fr/item/0501212}
}
Gesztesy, Fritz; Zinchenko, Maxim. A Borg-Type Theorem Associated with Orthogonal Polynomials on the Unit
Circle. arXiv, Tome 2005 (2005) no. 0, . http://gdmltest.u-ga.fr/item/0501212/