Hamburg 2009 – scientific programme

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A: Fachverband Atomphysik

A 15: Poster I

A 15.39: Poster

Tuesday, March 3, 2009, 16:30–19:00, VMP 9 Poster

The thermal Bose gas - a stochastic approach — •Sigmund Heller and Walter T. Strunz — Institut für Theoretische Physik, Universität Dresden

Temperature dependent quantities like spatial correlation functions [1], density fluctuations [2] and interference contrast [3] are measured in current experiments with ultracold Bose gases. In order to describe these experiments, we present a novel stochastic evolution equation, which enables us to obtain the thermal state of the canonical ensemble. The equation provides a full quantum field description and therefore does not suffer from cutoff problems, which usually occur for classical field equations. Furthermore, it is possible to solve the equation in position space with suitable effort - no knowledge of eigenfunctions or eigenenergies of the external potential is required. The equation is derived for the non interacting case, but drawing on analogies with the classical case, it is more than tempting to include the interaction in a mean field sense. We present numerical simulations for the ideal and for the interacting gas and calculate many different quantities like the ground state occupancy, variance of the ground state occupancy and spatial correlation functions.

[1] I. Bloch, T.W. Hänsch and T. Esslinger, Nature 403, 166 (2000).

[2] J. Esteve, J. B. Trebbia, T. Schumm, A. Apect, C. I. Westbrook, and I. Bouchle, Pyhs. Rev. Lett. 96, 130403 (2006).

[3] R. Gati, B. Hemmerling, J. Fölling, M. Albiez and M. K. Oberthaler, Phys. Rev. Lett. 96, 130404 (2006).