Analog vacuum decay from vacuum initial conditions

TL;DR

This paper demonstrates that ultracold atomic gases can serve as experimental analogs for relativistic vacuum decay, allowing empirical investigation of early-Universe phenomena through quantum fluctuations and bubble nucleation simulations.

Contribution

It extends previous classical analyses by incorporating quantum fluctuations and provides realistic experimental parameters for observing vacuum decay in cold-atom systems.

Findings

Quantum fluctuation spectrum matches relativistic results

Qualitative agreement between simulations and instanton predictions

Experimental setup can probe quantum decay at temperatures below 10 nK

Abstract

Ultracold atomic gases can undergo phase transitions that mimic relativistic vacuum decay, allowing us to empirically test early-Universe physics in tabletop experiments. We investigate the physics of these analog systems, going beyond previous analyses of the classical equations of motion to study quantum fluctuations in the cold-atom false vacuum. We show that the fluctuation spectrum of this vacuum state agrees with the usual relativistic result in the regime where the classical analogy holds, providing further evidence for the suitability of these systems for studying vacuum decay. Using a suite of semiclassical lattice simulations, we simulate bubble nucleation from this analog vacuum state in a 1D homonuclear potassium-41 mixture, finding qualitative agreement with instanton predictions. We identify realistic parameters for this system that will allow us to study vacuum decay with current experimental capabilities, including a prescription for efficiently scanning over decay rates, and show that this setup will probe the quantum (rather than thermal) decay regime at temperatures $T\lesssim10\,\mathrm{nK}$. Our results help lay the groundwork for using upcoming cold-atom experiments as a new probe of nonperturbative early-Universe physics.