One-Loop Dominance in the Imaginary Part of the Polarizability:   Application to Blackbody and Non-Contact van der Waals Friction
  Phenomenologically important quantum dissipative processes include black-body friction (an atom absorbs counterpropagating blue-shifted photons and spontaneously emits them in all directions, losing kinetic energy) and non-contact van der Waals friction (in the vicinity of a dielectric surface, the mirror charges of the constituent particles inside the surface experience drag, slowing the atom). The theoretical predictions for these processes are modified upon a rigorous quantum electrodynamic (QED) treatment, which shows that the one-loop "correction" yields the dominant contribution to the off-resonant, gauge-invariant, imaginary part of the atom's polarizability at room temperature, for typical atom-surface interactions. The tree-level contribution to the polarizability dominates at high temperature. 
U. D. Jentschura, G. Lach, M. De Kieviet, K. Pachucki
quant-ph