A dichotomy result about Hessenberg matrices associated with measures in the unit circle
A dichotomy result about Hessenberg matrices associated with measures in the unit circle
We characterize Hessenberg matrices D associated with measures in the unit circle ν , which are matrix representations of compact and actually Hilbert Schmidt perturbations of the forward shift operator as those with recursion coefficients verifying , ie, associated with measures verifying Szegö condition. As a consequence, we obtain the …