Perturbation theory in a deformed basis

Abstract

The total Hamiltonian H is written in two parts H = H0 + x Hres ( 0 ≤ x ≤ 1 ). We consider the case in which the basic set of states (eigenfunctions of H0) is deformed, i.e., [H,L] = O and [H0,L] ≠ O, where L can be the angular momentum, the number of particles, etc. In such cases perturbation theory of Hres converge.