Reheating in Inflationary Cosmology: Theory and Applications

TL;DR

The paper analyzes how the universe transitions from inflation to a hot, thermal state, focusing on both perturbative reheating and non-perturbative preheating via parametric resonance or tachyonic instabilities. It surveys the role of expanding backgrounds, backreaction, and turbulence in transferring energy from the inflaton to Standard Model fields, as well as the subsequent thermalization process. It then extends the discussion to supersymmetric frameworks, where flat directions can delay or modify decay and thermalization, and surveys cosmological consequences including non-thermal particle production, baryogenesis, dark matter, moduli/gravitino production, and gravitational waves. Overall, the work highlights that reheating is a highly model-dependent, multi-stage process with rapid early energy transfer but potentially long-lasting thermalization, shaping the early thermal history and observable signatures of the cosmos.

Abstract

Reheating is an important part of inflationary cosmology. It describes the production of Standard Matter particles after the phase of accelerated expansion. We give a review of the reheating process, focusing on an in-depth discussion of the preheating stage which is characterized by exponential particle production due to a parametric resonance or tachyonic instability. We give a brief overview of the thermalization process after preheating and end with a survey of some applications to supersymmetric theories and to other issues in cosmology such as baryogenesis, dark matter and metric preheating.

Figures (1)

• Figure 1: Instability bands of the Mathieu equation (from Mathieu). The horizontal axis is the parameter $q$ of (\ref{['mat']}), the vertical axis is the value of $A$. The shaded regions are regions in parameter space where there is a parametric resonance instability.