# Inflationary preheating dynamics with ultracold atoms

## TL;DR

This paper explores how dynamical instabilities in ultracold atom systems can amplify quantum loop corrections, drawing parallels to early-universe particle production, and proposes experimental protocols for observing these effects.

## Contribution

It provides a detailed analytical and numerical study of tachyonic instabilities in ultracold atoms, linking macroscopic growth to microscopic quantum processes, and suggests optimized experimental methods.

## Key findings

- Amplification of loop corrections via dynamical instabilities in ultracold gases.
- Establishment of a correspondence between growth rates and Feynman diagrams.
- Proposed protocols for experimental realization of instability-driven amplification.

## Abstract

We discuss the amplification of loop corrections in quantum many-body systems through dynamical instabilities. As an example, we investigate both analytically and numerically a two-component ultracold atom system in one spatial dimension. The model features a tachyonic instability, which incorporates characteristic aspects of the mechanisms for particle production in early-universe inflaton models. We establish a direct correspondence between measureable macroscopic growth rates for occupation numbers of the ultracold Bose gas and the underlying microscopic processes in terms of Feynman loop diagrams. We analyze several existing ultracold atom setups featuring dynamical instabilities and propose optimized protocols for their experimental realization. We demonstrate that relevant dynamical processes can be enhanced using a seeding procedure for unstable modes and clarify the role of initial quantum fluctuations and the generation of a non-linear secondary stage for the amplification of modes.