Tachyonic production of dark relics: classical lattice vs. quantum 2PI in Hartree truncation

TL;DR

This paper compares classical lattice simulations and quantum 2PI Hartree truncation methods to study the non-equilibrium production of scalar dark matter during reheating, finding qualitative agreement and a dominant non-linear resonance effect.

Contribution

It demonstrates that classical lattice simulations can replicate key features of quantum 2PI Hartree results in dark matter production, highlighting the role of non-linear resonance.

Findings

Classical simulations agree qualitatively with quantum 2PI results.

Non-linear resonance significantly influences dark matter yield.

Differences in scalar two-point functions are within a factor of O(1).

Abstract

We study the out-of-equilibrium production of non-minimally coupled self-interacting scalar dark matter during reheating using classical lattice simulations. The outcomes of the classical simulations are in qualitative agreement with the previous results obtained using the quantum 2PI approach in the Hartree truncation. In particular, the novel non-linear resonance found in the 2PI Hartee study is present also in the classical lattice simulations and can dominate the final dark matter yield. For the parameters considered, the difference in final value of the scalar two-point function between the two approaches is a factor of O(1).