Cantor spectrum for CMV and Jacobi matrices with coefficients arising from generalized skew-shifts

Cantor Spectrum for Schrödinger Operators with Potentials Arising from Generalized Skew-shifts

We consider continuous SL(2,R)-cocycles over a strictly ergodic homeomorphism which fibers over an almost periodic dynamical system (generalized skew-shifts). We prove that any cocycle which is not uniformly hyperbolic can be approximated by one which is conjugate to an SO(2,R)-cocycle. Using this, we show that if a cocycle’s homotopy class does not display a certain obstruction to uniform hype...

Cmv: the Unitary Analogue of Jacobi Matrices

Abstract. We discuss a number of properties of CMV matrices, by which we mean the class of unitary matrices recently introduced by Cantero, Moral, and Velazquez. We argue that they play an equivalent role among unitary matrices to that of Jacobi matrices among all Hermitian matrices. In particular, we describe the analogues of well-known properties of Jacobi matrices: foliation by co-adjoint or...

Two modified Jacobi methods for M-matrices

On Generalized Sum Rules for Jacobi Matrices

This work is in a stream (see e.g. [4], [8], [10], [11], [7]) initiated by a paper of Killip and Simon [9], an earlier paper [5] also should be mentioned here. Using methods of Functional Analysis and the classical Szegö Theorem we prove sum rule identities in a very general form. Then, we apply the result to obtain new asymptotics for orthonormal polynomials.

The Essential Spectrum of Schrödinger, Jacobi, and Cmv Operators

We provide a very general result that identifies the essential spectrum of broad classes of operators as exactly equal to the closure of the union of the spectra of suitable limits at infinity. Included is a new result on the essential spectra when potentials are asymptotic to isospectral tori. We also recover with a unified framework the HVZ theorem and Krein’s results on orthogonal polynomial...