Anisotropic Inflation in Dipolar Bose-Einstein Condensates

TL;DR

This paper proposes using dipolar Bose-Einstein condensates as a laboratory platform to simulate and study the evolution of anisotropic inflationary fluctuations, linking condensate interactions to cosmological scale factors.

Contribution

It introduces a novel analogy between dipolar BEC sound wave anisotropy and cosmological inflation, enabling controlled experiments on anisotropy evolution.

Findings

Derived an anisotropic space-time metric for BEC sound waves.

Calculated phonon power spectra dynamics during simulated inflation.

Showed that expansion speed controls residual anisotropy.

Abstract

Early during the era of cosmic inflation, rotational invariance may have been broken, only later emerging as a feature of low-energy physics. This motivates ongoing searches for residual signatures of anisotropic space-time, for example in the power spectrum of the cosmic microwave background. We propose that dipolar Bose-Einstein condensates (BECs) furnish a laboratory quantum simulation platform for the anisotropy evolution of fluctuation spectra during inflation, exploiting the fact that the speed of dipolar condensate sound waves depends on direction. We construct the anisotropic analogue space-time metric governing sound, by linking the time-varying strength of dipolar and contact interactions in the BEC to the scale factors in different coordinate directions. Based on these, we calculate the dynamics of phonon power spectra during an inflation that renders the initially anisotropic universe isotropic. We find that the expansion speed provides an experimental handle to control and study the degree of final residual anisotropy. Gravity analogues using dipolar condensates can thus provide tuneable experiments for a field of cosmology that was until now confined to a single experiment, our universe.