A consistent method for the perturbative calculation of scattering amplitudes in hot gauge theories is developed. It involves the resummation of a subset of thermal fluctuations, termed hard thermal loops, into effective propagators and vertices. The damping rate of a heavy fermion is computed as an example.

• Received 21 November 1988

DOI:https://doi.org/10.1103/PhysRevLett.63.1129