Dissipation coefficients from scalar and fermion quantum field interactions

TL;DR

This paper calculates dissipation coefficients in quantum field interactions relevant to warm inflation, analyzing two temperature regimes and discussing implications for cosmology and phase transitions.

Contribution

It provides a detailed derivation of dissipation coefficients for scalar and fermion interactions in both high and low temperature regimes, addressing resummation challenges.

Findings

Derived dissipation coefficients for high and low temperature regimes.

Identified regimes where spectral function approximations are valid.

Discussed applications to cosmological phase transitions.

Abstract

Dissipation coefficients are calculated in the adiabatic, near thermal equilibrium regime for a large class of renormalizable interaction configurations involving a two-stage mechanism, where a background scalar field is coupled to heavy intermediate scalar or fermion fields which in turn are coupled to light scalar or fermion radiation fields. These interactions are typical of warm inflation microscopic model building. Two perturbative regimes are shown where well defined approximations for the spectral functions apply. One regime is at high temperature, when the masses of both intermediate and radiation fields are less than the temperature scale and where the poles of the spectral functions dominate. The other regime is at low temperature, when the intermediate field masses are much bigger than the temperature and where the low energy and low three-momentum regime dominate the spectral functions. The dissipation coefficients in these two regimes are derived. However, due to resummation issues for the high temperature case, only phenomenological approximate estimates are provided for the dissipation in this regime. In the low temperature case, higher loop contributions are suppressed and so no resummation is necessary. In addition to inflationary cosmology, the application of our results to cosmological phase transitions is also discussed.