Dissipation coefficients from scalar and fermion quantum field interactions

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.In Press JCAP (2011).

Reheating dynamics affects non-perturbative decay of spectator fields

“…while the inflaton is decaying; in the radiation-dominated era the relative contribution will fall again. 9 Note that in the radiation-dominated era, the blocking term again decreases in magnitude, and we expect the resonance to become unblocked a second time as in [8].…”

“…The topic of the perturbative dissipation of a scalar in a thermal background has been studied in the context of warm inflation [9]. Related work [10] discusses thermal effects on an oscillating scalar field coupled to a generic fermion, covering the dissipative effect of the thermal bath, modification of the scalar potential, the formation of non-topological solitons and non-perturbative particle production.…”

Adiabatic out-of-equilibrium solutions to the Boltzmann equation in warm inflation

“…In addition, we have recently shown that warm inflation can be consistently realized in a simple quantum field theory framework requiring very few fields, the Warm Little Inflaton scenario [19], where the required flatness of the inflaton potential is not spoiled by thermal effects (see also refs. [20][21][22][23][24][25][26] for earlier alternative models), paving the way for developing a complete particle physics description of inflation that can be fully tested with CMB and Large-Scale Structure (LSS) observations and possibly have implications for collider and particle physics data.…”

“…We neglect all chemical potentials for simplicity. The corresponding decay widths are given by [23] Γ (B)…”

“…This is required for consistently using equilibrium phase-space distribution functions to compute the associated dissipation coefficients (see, e.g., refs. [23,25]). Typically this requires such particles to decay faster than the Hubble rate, posing constraints on the coupling constants and particle masses considered that could be relaxed if out-of-equilibrium distribution functions are known.…”