Dynamical renormalization group resummation of finite temperature infrareddivergences - art. no. 065003

We introduce the method of dynamical renormalization group to study relaxat ion and damping out of equilibrium directly in real time and apply it to th e study of infrared divergences in scalar QED. This method allows a consist ent resummation of infrared effects associated with the exchange of quasist atic transverse photons and leads to anomalous logarithmic relaxation of th e form e(-alpha T t ln[t/t0]) for hard momentum charged excitations. This i s in contrast with the usual quasiparticle interpretation of charged collec tive excitations at finite temperature in the sense of exponential relaxati on of a narrow width resonance for which the width is the imaginary part of the self-energy on shell. In the case of narrow resonances away from thres holds, this approach leads to the usual exponential relaxation. The hard th ermal loop resummation program is incorporated consistently into the dynami cal renormalization group yielding a picture of relaxation and damping phen omena in a plasma in real time that transcends the conceptual limitations o f the quasiparticle picture and other types of resummation schemes. [S0556- 2821(99)02516-3].