Quantum backreaction in dilute Bose-Einstein condensates

TL;DR

This paper examines the quantum backreaction problem in dilute Bose-Einstein condensates, revealing limitations of the effective-action approach and emphasizing the importance of the pseudo-energy-momentum tensor for accurate description.

Contribution

It demonstrates that the effective-action method is insufficient for quantum backreaction in BECs and highlights the need for the pseudo-energy-momentum tensor for correct modeling.

Findings

Effective-action technique does not always give correct backreaction results.

Knowledge of the pseudo-energy-momentum tensor alone is insufficient.

Highlights limitations of existing theoretical approaches in BEC quantum backreaction.

Abstract

For many physical systems which can be approximated by a classical background field plus small (linearized) quantum fluctuations, a fundamental question concerns the correct description of the backreaction of the quantum fluctuations onto the dynamics of the classical background. We investigate this problem for the example of dilute atomic/molecular Bose-Einstein condensates, for which the microscopic dynamical behavior is under control. It turns out that the effective-action technique does not yield the correct result in general and that the knowledge of the pseudo-energy-momentum tensor ${<\hat T_{\mu\nu}>}$ is not sufficient to describe quantum backreaction.