An inverse spectral problem for non-self-adjoint Jacobi matrices

Abstract

We consider the class of bounded symmetric Jacobi matrices $J$ with positive off-diagonal elements and complex diagonal elements. With each matrix $J$ from this class, we associate the spectral data, which consists of a pair $(\nu,\psi)$. Here $\nu$ is the spectral measure of $|J|=\sqrt{J^*J}$ and $\psi$ is a $\textit{phase function}$ on the real line satisfying $|\psi|\leq1$ almost everywhere with respect to the measure $\nu$. Our main result is that the map from $J$ to the pair $(\nu,\psi)$ is a bijection between our class of Jacobi matrices and the set of all spectral data.