Non-Thermal Production of Dangerous Relics in the Early Universe

TL;DR

This paper investigates how non-thermal processes in the early universe can produce dangerous relic particles, such as moduli and gravitinos, more efficiently than thermal mechanisms, leading to stricter constraints on the reheating temperature.

Contribution

It demonstrates that non-thermal production mechanisms can dominate relic generation, significantly tightening bounds on reheating temperatures in supersymmetric cosmology.

Findings

Non-thermal production of relics can be more efficient than thermal processes.

Reheating temperature bounds can be as low as 100 GeV due to non-thermal effects.

Non-thermal gravitino production can surpass thermal production by several orders of magnitude.

Abstract

Many models of supersymmetry breaking, in the context of either supergravity or superstring theories, predict the presence of particles with weak scale masses and Planck-suppressed couplings. Typical examples are the scalar moduli and the gravitino. Excessive production of such particles in the early Universe destroys the successful predictions of nucleosynthesis. In particular, the thermal production of these relics after inflation leads to a bound on the reheating temperature, T_{RH} < 10^9 GeV. In this paper we show that the non-thermal generation of these dangerous relics may be much more efficient than the thermal production after inflation. Scalar moduli fields may be copiously created by the classical gravitational effects on the vacuum state. Consequently, the new upper bound on the reheating temperature is shown to be, in some cases, as low as 100 GeV. We also study the non-thermal production of gravitinos in the early Universe, which can be extremely efficient and overcome the thermal production by several orders of magnitude, in realistic supersymmetric inflationary models.