Generalizações do truque de Kotani

Abstract

We present a study of rank-one perturbations of self-adjoint and unitary operators, in particular related to the so-called Kotani’s trick. In Chapter 2 we recall relevant definitions and elementary facts. In Chapter 3 we present recent results by Marx, which involve self-adjoint operators and Hausdorff measures. A generalization of such results to the set of unitary operators is described in Chapter 4.