# Symmetric and Asymmetric Reheating

## TL;DR

This paper investigates how inflaton coupling to multiple sectors affects their energy distribution during reheating, revealing conditions for asymmetric reheating and implications for dark matter models.

## Contribution

It introduces a comprehensive analysis of symmetric and asymmetric reheating effects in models with multiple sectors coupled to the inflaton.

## Key findings

- Preheating often occurs without disruption by extra sectors.
- Weakly coupled sectors can acquire significant energy fractions.
- Asymmetric reheating can lead to large temperature differences between sectors.

## Abstract

We study models in which the inflaton is coupled to two otherwise decoupled sectors, and the effect of preheating and related processes on their energy densities during the evolution of the universe. Over most of parameter space, preheating is not disrupted by the presence of extra sectors, and even comparatively weakly coupled sectors can get an order 1 fraction of the total energy at this time. If two sectors are both preheated, the high number densities could also lead to inflaton mediated thermalisation. If only one sector is preheated, Bose enhancement of the late time inflaton decays may cause significant deviations from the perturbative prediction for their relative reheat temperatures. Meanwhile, in Non-Oscillatory inflation models resonant effects can result in exponentially large final temperature differences between sectors that have similar couplings to the inflaton. Asymmetric reheating is potentially relevant for a range of beyond the Standard Model physics scenarios. We show that in dark matter freeze-in models, hidden sector temperatures a factor of 10 below that of the visible sector are typically needed for the relic abundance to be set solely by freeze-in dynamics.