Tachyonic production of dark relics: a non-perturbative quantum study

TL;DR

This paper investigates the non-perturbative quantum production of dark relics during reheating after inflation, highlighting the dominance of parametric instability driven by the two-point function and its sensitivity to model parameters.

Contribution

It derives and numerically solves renormalized quantum transport equations for a non-minimally coupled scalar field, revealing new features of parametric instability in dark relic production.

Findings

Parametric instability can dominate particle production during reheating.

The system exhibits both tachyonic and parametric instabilities, with the latter driven by the two-point function.

Results are highly sensitive to the model parameters.

Abstract

We study production of dark relics during reheating after the end of inflation in a system consisting of a non-minimally coupled spectator scalar field and the inflaton. We derive a set of renormalized quantum transport equations for the one-point function and the two-point function of the spectator field and solve them numerically. We find that our system can embody both tachyonic and parametric instabilities. The former is an expected result due to the non-minimal coupling, but the latter displays new features driven by a novel interplay of the two-point function with the Ricci scalar. We find that when the parametric instability driven by the two-point function takes place, it dominates the total particle production. The quantitative results are also found to be highly sensitive to the model parameters.