Kinetic Theory of Collective Modes in Atomic Clouds above the Bose-Einstein Transition Temperature

TL;DR

This paper derives a unified description of collective mode frequencies and damping rates in a dilute Bose gas above the BEC transition, bridging collisionless and hydrodynamic regimes, with explicit formulas for axially symmetric traps.

Contribution

It provides a new dispersion relation for collective modes in Bose gases that interpolates between different collisional regimes, validated by microscopic calculations and experiments.

Findings

Explicit expressions for mode frequencies and damping rates

Validation against microscopic calculations

Agreement with experimental data

Abstract

We calculate frequencies and damping rates of the lowest collective modes of a dilute Bose gas confined in an anisotropic trapping potential above the Bose-Einstein transition temperature. From the Boltzmann equation with a simplified collision integral we derive a general dispersion relation that interpolates between the collisionless and hydrodynamic regimes. In the case of axially symmetric traps we obtain explicit expressions for the frequencies and damping rates of the lowest modes in terms of a phenomenological collision time. Our results are compared with microscopic calculations and experiments.