Condensate decay in a radiation dominated cosmology

Abstract

We study the decay of a homogeneous condensate of a massive scalar field of mass \emph{m} into massless fields in thermal equilibrium in a radiation dominated cosmology. The model is a \emph{proxy} for the non-equilibrium dynamics of a misaligned axion condensate decaying into radiation. After consistent field quantization in the cosmological background, we obtain the causal equations of motion for a homogeneous condensate including the finite temperature self-energy corrections up to one loop. The dynamical renormalization group is implemented to obtain the time dependent relaxation rate that describes the decay dynamics of the condensate amplitude from stimulated emission and recombination of massless quanta in the medium. It is explicitly shown that a simple friction term in the equation of motion does not describe correctly the decay of the condensate. During the super-Hubble regime, relevant for ultralight dark matter, the condensate amplitude decays as $e^{-\frac{g^2}{10}{t}^2\ln (1/mt)}$. In the sub-Hubble regime the amplitude decays as $e^{-\gamma (t;T(t))/2}$ with $T(t)=T_0/a(t)$, therefore the finite temperature contribution to the decay rate vanishes fast during the expansion. A main conclusion is that a phenomenological friction term is inadequate to describe the decay in the super-Hubble regime, the decay function $\gamma (t)$ is always \emph{smaller} than that from a local friction term as a consequence of the cosmological expansion. For ultra light dark matter, the time scale during which transient dynamics is sensitive to cosmological expansion and a local friction term is inadequate, is much longer. A friction term always \emph{underestimates} the time scale of decay in the sub-Hubble case.

References in corpus (28)

• First Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Determination of Cosmological Parameters
• Planck 2015 results. XIII. Cosmological parameters
• Nine-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Final Maps and Results
• Axion Cosmology
• Cold and Fuzzy Dark Matter
• Ultralight scalars as cosmological dark matter
• Reheating in Inflationary Cosmology: Theory and Applications
• Nonperturbative Dynamics Of Reheating After Inflation: A Review
• Invisible Axion Search Methods
• Warm Inflation and its Microphysical Basis
• Parametric Amplification of Metric Fluctuations During Reheating in Two Field Models
• Reheating the Universe after String Theory Inflation
• Dynamical renormalization group approach to relaxation in quantum field theory
• Reheating the Universe After Multi-Field Inflation
• An ultralight pseudoscalar boson
• Particle decay during inflation: self-decay of inflaton quantum fluctuations during slow roll
• Particle decay in inflationary cosmology
• Fate of $Z_2$ Symmetric Scalar Field
• Real-time nonequilibrium dynamics in hot QED plasmas: dynamical renormalization group approach
• Non-equilibrium dynamics of Axion-like particles: the quantum master equation
• Dynamical renormalization group approach to transport in ultrarelativistic plasmas: the electrical conductivity in high temperature QED
• Decay of a Massive Particle in a Stiff Matter Dominated Universe
• Particle decay in post inflationary cosmology
• Decaying Massive Particle in Matter and Radiation Dominated Eras
• Brownian Axion-like particles
• Particle decay in expanding Friedmann-Robertson-Walker universes
• Cosmological decay of Higgs-like scalars into a fermion channel
• Interaction rates in cosmology: heavy particle production and scattering