Scalar Trapping and Saxion Cosmology

TL;DR

This paper investigates the dynamics of scalar fields in thermal environments with symmetry breaking, focusing on saxion trapping and its implications for thermal inflation and axion overproduction.

Contribution

It provides a detailed analysis of scalar trapping mechanisms, especially for saxions, and explores their effects on thermal inflation and axion cosmology.

Findings

Saxion trapping occurs in most cases with large initial amplitudes.

Thermal inflation is often triggered by saxion trapping.

Thermal dissipation can mitigate axion overproduction from saxion decay.

Abstract

We study in detail the dynamics of a scalar field in thermal bath with symmetry breaking potential. In particular, we focus on the process of trapping of a scalar field at an enhanced symmetry point through the thermal/non-thermal particle production, taking into account the interactions of produced particles with the standard model particles. As an explicit example, we revisit the saxion dynamics with an initial amplitude much larger than the Peccei-Quinn scale and show that the saxion trapping phenomenon happens for the most cases and it often leads to thermal inflation. We also study the saxion dynamics after thermal inflation, and it is shown that thermal dissipation effect on the saxion can relax the axion overproduction problem from the saxion decay.