BEC Collapse and Dynamical Squeezing of Vacuum Fluctuations

TL;DR

This paper explains Bose Novae phenomena by analyzing how condensate dynamics amplify quantum fluctuations, leading to particle bursts and jets, with results aligning well with experimental data and implications for laboratory cosmology.

Contribution

It introduces a simple physical model based on a test field approximation that explains Bose Novae features and fits experimental data, highlighting the role of vacuum fluctuation amplification.

Findings

Quantitative agreement with collapse time scaling

Accurate modeling of particle content in jets

Identification of parametric amplification as key mechanism

Abstract

We analyze the phenomena of Bose Novae, as described by Donley et al [Nature 412, 295 (2001)], by focusing on the behavior of excitations or fluctuations above the condensate, as driven by the dynamics of the condensate (rather than the dynamics of the condensate alone or the kinetics of the atoms). The dynamics of the condensate squeezes and amplifies the quantum excitations, mixing the positive and negative frequency components of their wave functions thereby creating particles which appear as bursts and jets. By analyzing the changing amplitude and particle content of these excitations, our simple physical picture (based on a test field approximation) explains well the overall features of the Bose Novae phenomena and provide excellent quantitative fits with experimental data on several aspects, such as the scaling behavior of the collapse time and the amount of particles in the jet. The predictions of the bursts at this level of approximation is less than satisfactory but may be improved on by including the backreaction of the excitations on the condensate. The mechanism behind the dominant effect -- parametric amplification of vacuum fluctuations and freezing of modes outside of horizon -- is similar to that of cosmological particle creation and structure formation in a rapid quench (which is fundamentally different from Hawking radiation in black holes). This shows that BEC dynamics is a promising venue for doing `laboratory cosmology'.