# Reheating in two-sector cosmology

## TL;DR

This paper investigates the dynamics of reheating in two-sector cosmology, focusing on quantum statistical effects and inflaton-mediated energy transfer, providing new power laws and analytic estimates for temperature evolution and asymmetry.

## Contribution

It introduces comprehensive numerical solutions including quantum statistics and develops new analytical estimates for temperature asymmetries in two-sector reheating scenarios.

## Key findings

- Quantum statistical effects significantly influence temperature evolution.
- Inflaton-mediated scattering is dominant at specific temperature regimes.
- Classical reheating approximates asymmetry well at low temperatures.

## Abstract

We analyze reheating scenarios where a hidden sector is populated during reheating along with the sector containing the Standard Model. We numerically solve the Boltzmann equations describing perturbative reheating of the two sectors, including the full dependence on quantum statistics, and study how quantum statistical effects during reheating as well as the non-equilibrium inflaton-mediated energy transfer between the two sectors affects the temperature evolution of the two radiation baths. We obtain new power laws describing the temperature evolution of fermions and bosons when quantum statistics are important during reheating. We show that inflaton-mediated scattering is generically most important at radiation temperatures $T\sim M_\phi/4$, and build on this observation to obtain analytic estimates for the temperature asymmetry produced by asymmetric reheating. We find that for reheating temperatures $T_{\textrm{rh}} \ll M_{\phi}/4$, classical perturbative reheating provides an excellent approximation to the final temperature asymmetry, while for $T_{\textrm{rh}}\gg M_{\phi}/4$, inflaton-mediated scattering dominates the population of the colder sector and thus the final temperature asymmetry. We additionally present new techniques to calculate energy transfer rates between two relativistic species at different temperatures.