Collective oscillations of a classical gas confined in harmonic traps

https://pro.college-de-france.fr/jean.dalibard/publications/collective99.pdfInternational audienceStarting from the Boltzmann equation we calculate the frequency and the damping of the monopole and quadrupole oscillations of a classical gas confined in an harmonic potential. The collisional term is treated in the relaxation time approximation and a gaussian ansatz is used for its evaluation. Our approach provides an explicit description of the transition between the hydrodynamic and collisionless regimes in both spherical and deformed traps. The predictions are compared with the results of a numerical simulation