Adiabatic perturbation theory for the degenerate case. III. Adiabatic formalism by Gell‐Mann and low with an arbitrary switching function

Abstract

AbstractAn adiabatic formalism in the degenerate or quasidegenerate subspaces, which does not depend on the particular form of the switching function g(α, t), is outlined. A general factorization theorem for the dynamic operator Sα(t, t0 | g) is proved. This theorem enables one to formulate the perturbation expansion for the effective Hamiltonian and the wave operator which is free from the adiabatic divergencies.