title: Experimental evidence for the breakdown of a Hartree-Fock approach in a weakly interacting Bose gas.
abstract: We investigate the physics underlying the presence of a quasicondensate in a nearly one dimensional, weakly interacting trapped atomic Bose gas. We show that a Hartree-Fock (mean-field) approach fails to predict the existence of the quasicondensate in the center of the cloud: the quasicondensate is generated by interaction-induced correlations between atoms and not by a saturation of the excited states. Numerical calculations based on Bogoliubov theory give an estimate of the crossover density in agreement with experimental results.
authors.affiliation: Laboratoire Charles Fabry, CNRS et Université Paris 11, 91403 Orsay CEDEX, France.
authors.forename: J-B
authors.initials: JB
authors.lastname: Trebbia
authors.forename: J
authors.initials: J
authors.lastname: Esteve
authors.forename: C I
authors.initials: CI
authors.lastname: Westbrook
authors.forename: I
authors.initials: I
authors.lastname: Bouchoule