Changing the discrete spectrum of the half-line matrix Schrödinger operator

Abstract

We consider the matrix-valued Schrödinger operator on the half line with the general selfadjoint boundary condition. When the discrete spectrum is changed without changing the continuous spectrum, we present a review of the transformations of the relevant quantities including the regular solution, the Jost solution, the Jost matrix, the scattering matrix, and the boundary matrices used to describe the selfadjoint boundary condition. The changes in the discrete spectrum are considered when an existing bound state is removed, a new bound state is added, and the multiplicity of a bound state is decreased or increased without removing the bound state. We provide various explicit examples to illustrate the theoretical resultspresented.