Two mechanisms for the elimination of pinch singularities in out of equilibrium thermal field theories

Abstract

We analyze ill-defined pinch singularities characteristic of out of equilibrium thermal field theories. We identify two mechanisms that eliminate pinching even at the single self-energy insertion approximation to the propagator: the first is based on the vanishing of phase space at the singular point (threshold effect). It is effective in QED with a massive electron and a massless photon. In massless QCD, this mechanism fails, but the pinches cancel owing to the second mechanism, i.e., owing to the spinor/tensor structure of the single self-energy insertion contribution to the propagator. The constraints imposed on distribution functions are very reasonable.

24 pages, Latex, no figures, revised version, many minor changes and corrections

References in corpus (3)

• Thermal photon production rate from non-equilibrium quantum field theory
• Structure of the Gluon Propagator at Finite Temperature
• Renormalization of number density in nonequilibrium quantum-field theory and absence of pinch singularities

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