Third-order many-body perturbation theory calculations of the ground-state energies of cesium and thallium

A detailed breakdown of many-body perturbation theory contributions through third order is presented for the ground-state removal energies of cesium and thallium, with the aim of identifying which Goldstone diagrams are numerically dominant. A comparison of these diagrams with Feynman graphs is made. A discussion of the issues involved in carrying out ab initio calculations of properties of these atoms accurate at the few tenths of a percent level is presented.