05-17 Fritz Gesztesy and Maxim Zinchenko

A Borg-Type Theorem Associated with Orthogonal Polynomials on the Unit Circle (105K, LaTeX) Jan 13, 05

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Abstract. 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.

Files: 05-17.tex