Computational determination of wave operators from large Hamiltonian matrices†
Abstract
Quantum
perturbation theory is reviewed in the framework of wave operators which are ubiquitous from bound states
to scattering theory. The wave operators are determined by the iterative solution of non-linear Bloch equations. The convergence properties are improved by means of polynomial approximations of Newton–Raphson
factors. Our approach is discussed with respect to other iterative methods. A numerical
illustration is presented for two model problems: the determination
of low-frequency
normal modes in