Sound Propagation in Elongated Bose-Einstein Condensed Clouds

TL;DR

This paper investigates sound pulse propagation in elongated Bose-Einstein condensates, analyzing linear and nonlinear regimes, and deriving how pulse speed depends on local properties and amplitude.

Contribution

It provides a detailed analysis of sound propagation in elongated BECs, including the effects of nonlinearity on pulse speed, which was not previously characterized.

Findings

Velocity squared equals the averaged local sound velocity squared.

Nonlinear effects alter the pulse speed depending on amplitude.

The study extends understanding of sound dynamics in anisotropic BECs.

Abstract

We consider propagation of sound pulses along the long axis of a Bose-Einstein condensed cloud in a very anisotropic trap. In the linear regime, we demonstrate that the square of the velocity of propagation is given by the square of the local sound velocity, $c^2=nU_0/m$, averaged over the cross section of the cloud. We also carry out calculations in the nonlinear regime, and determine how the speed of the pulse depends on its amplitude.