Thermalization Process after Inflation and Effective Potential of Scalar Field

TL;DR

This paper studies the Universe's thermalization after inflation, revealing that delayed thermalization leads to lower maximum temperatures, affecting particle production, symmetry restoration, and early Universe mechanisms.

Contribution

It provides a detailed analysis of the delayed thermalization process and its impact on the effective potential and maximum temperature of the Universe after inflation.

Findings

Maximum temperature can be as low as electroweak scale for low reheating temperatures.

Delayed thermalization significantly reduces the maximum temperature compared to previous estimates.

Implications for dark matter production, electroweak symmetry restoration, and baryogenesis mechanisms.

Abstract

We investigate the thermalization process of the Universe after inflation to determine the evolution of the effective temperature. The time scale of thermalization is found to be so long that it delays the evolution of the effective temperature, and the resulting maximal temperature of the Universe can be significantly lower than the one obtained in the literature. Our results clarify the finite density corrections to the effective potential of a scalar field and also processes of heavy particle production. In particular, we find that the maximum temperature of the Universe may be at most electroweak scale if the reheating temperature is as low as ${\cal O} (1)$ MeV, which implies that the electroweak symmetry may be marginally restored. In addition, it is noticeable that the dark matter may not be produced from thermal plasma in such a low reheating scenario, since the maximum temperature can be smaller than the conventional estimation by five orders of magnitude. We also give implications to the Peccei-Quinn mechanism and the Affleck-Dine baryogenesis.