Quasi-one-dimensional character of sound propagation in elongated Bose-Einstein condensed clouds
G. M. Kavoulakis, C. J. Pethick
Physical Review A. Atomic, Molecular, and Optical Physics
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.