There is a wide-spread belief in the literature on Bose-Einstein condensation of interacting atoms that all variants of mean-field theory incorrectly describe the condensation phase transition, exhibiting, instead of the necessary second-order transition, a first-order transition, even for weakly interacting Bose gas. In the present paper, it is shown that a self-consistent mean-field approach ...

Mesoscopic phenomena—including population oscillations and persistent currents driven by quantal phases—are explored theoretically in the context of multiply connected Bose-Einstein systems composed of trapped alkali-metal gas atoms. These atomic phenomena are bosonic analogs of electronic persistent currents in normal metals and Little-Parks oscillations in superconductors. Differences between...

We report in situ measurements of density fluctuations in a quasi-one-dimensional 87Rb Bose gas at thermal equilibrium in an elongated harmonic trap. We observe an excess of fluctuations compared to the shot-noise level expected for uncorrelated atoms. At low atomic density, the measured excess is in good agreement with the expected "bunching" for an ideal Bose gas. At high density, the measure...

We compute the scattering properties of rubidium atoms at ultracold temperatures, placing special emphasis on the radioactive isotopes Rb,Rb,Rb, and Rb. In combination with the more ‘‘conventional’’ isotope Rb, these species yield a wide variety of scattering behavior, with consequences for creating mixtures of Fermi-Fermi, Fermi-Bose, and Bose-Bose gases. In each of these mixtures we find at l...

We study the fluctuation of the number of particles in ideal Bose–Einstein condensates, both within the canonical and the microcanonical ensemble. Employing the Mellin–Barnes transformation, we derive simple expressions that link the canonical number of condensate particles, its fluctuation, and the difference between canonical and microcanonical fluctuations to the poles of a Zeta function tha...

We analyze the coherent multimode dynamics of a system of coupled atomic and molecular Bose gases. Starting from an atomic Bose-Einstein condensate with a small thermal component, we observe a complete depletion of the atomic and molecular condensate modes on a short time scale due to a significant population of excited states. Giant coherent oscillations between the two condensates for typical...

Using continuous radio-frequency waves a coherent beam of atoms can be extracted from a magnetically trapped gaseous Bose-Einstein condensate. These novel atomic beams have matter-wave properties that are very similar to those of laser light in classical optics and are therefore called atom lasers. Furthermore, coupling out atoms from a Bose gas allows one to probe the dramatic changes in the p...

A commonly used theoretical definition of superfluidity in the ground state of a Bose gas is based on the response of the system to an imposed velocity field or, equivalently, to twisted boundary conditions in a box. We are able to carry out this program in the case of a dilute interacting Bose gas in a trap. We prove that a gas with repulsive interactions is 100% superfluid in the dilute limit...

In 2005, we have made further progress in the studies of atom correlations in one-dimensional (1D) Bose gases [1]. We have calculated the density profiles and density correlation functions of a harmonically trapped (nonuniform) 1D Bose gas, using the exact finite-temperature solutions for the uniform case and applying a local density approximation. The results are valid for a trapping potential...