Numerical studies of back-reaction effects in an analog model of cosmological pre-heating

TL;DR

This paper models back-reaction effects during early Universe pre-heating using a Bose-Einstein condensate, revealing how excitations cause effective friction and coherence loss, challenging semiclassical descriptions.

Contribution

It introduces a novel analog model using a 2D ring-shaped BEC to simulate back-reaction effects in cosmological pre-heating, including numerical analysis of dynamics.

Findings

Exponential growth of dipole and Goldstone excitations due to parametric pair creation.

Back-reaction causes effective friction of the inflaton analog in the BEC.

Loss of spatial coherence in excitations impacts semiclassical back-reaction models.

Abstract

We theoretically propose an atomic Bose-Einstein condensate as an analog model of back-reaction effects during the pre-heating stage of early Universe. In particular, we address the out-of-equilibrium dynamics where the initially excited inflaton field decays by parametrically exciting the matter fields. We consider a two-dimensional, ring-shaped BEC under a tight transverse confinement whose transverse breathing mode and the Goldstone and dipole excitation branches simulate the inflaton and quantum matter fields, respectively. A strong excitation of the breathing mode leads to an exponentially-growing emission of dipole and Goldstone excitations via parametric pair creation: our numerical simulations of the BEC dynamics show how the associated back-reaction effect not only results in an effective friction of the breathing mode but also in a quick loss of longitudinal spatial coherence of the initially in-phase excitations. Implications of this result on the validity of the usual semiclassical description of back-reaction are finally discussed.