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Article Dans Une Revue The European Physical Journal B: Condensed Matter and Complex Systems Année : 1999

Bose-Einstein condensation in interacting gases

Résumé

We study the occurrence of a Bose-Einstein transition in a dilute gas with repulsive interactions, starting from temperatures above the transition temperature. The formalism, based on the use of Ursell operators, allows us to evaluate the one-particle density operator with more flexibility than in mean-field theories, since it does not necessarily coincide with that of an ideal gas with adjustable parameters (chemical potential, etc.). In a first step, a simple approximation is used (Ursell-Dyson approximation), which allow us to recover results which are similar to those of the usual mean-field theories. In a second step, a more precise treatment of the correlations and velocity dependence of the populations in the system is elaborated. This introduces new physical effects, such as a change of the velocity profile just above the transition: the proportion of atoms with low velocities is higher than in an ideal gas. A consequence of this distortion is an increase of the critical temperature (at constant density) of the Bose gas, in agreement with those of recent path integral Monte-Carlo calculations for hard spheres.

Dates et versions

hal-00001409 , version 1 (27-04-2004)

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Markus Holzmann, Peter Grüter, Franck Laloë. Bose-Einstein condensation in interacting gases. The European Physical Journal B: Condensed Matter and Complex Systems, 1999, 10, pp.739. ⟨hal-00001409⟩
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