Two-loop self-energy and multiple scattering at finite temperature - art. no. 045008

One- and two-loop self-energies are worked out explicitly for a heavy scala r field interacting weakly with a light self-interacting scalar field at fi nite temperature. The ring or daisy diagrams and a set of necklace diagrams can be summed simultaneously. This simple model serves to illustrate the c onnection between multiloop self-energy diagrams and multiple scattering in a medium.