We measure the zero-temperature equation of state of a homogeneous Bose gas of (7)Li atoms by analyzing the in situ density distributions of trapped samples. For increasing repulsive interactions our data show a clear departure from mean-field theory and provide a quantitative test of the many-body corrections first predicted in 1957 by Lee, Huang, and Yang [Phys. Rev. 106, 1135 (1957).]. We fu...

We report the creation of a Bose-Einstein condensate using buffer-gas cooling, the first realization of Bose-Einstein condensation using a broadly general method which relies neither on laser cooling nor unique atom-surface properties. Metastable helium ((4)He*) is buffer-gas cooled, magnetically trapped, and evaporatively cooled to quantum degeneracy. 10(11) atoms are initially trapped, leadin...

The idea is advanced that strong perturbations of an initially equilibrium Bose-condensed gas lead to the sequence of nonequilibrium states whose order is inverse to the sequence of states arising in the process of the Bose-gas relaxation from an initial nonequilibrium state. An approach is described for constructing statistical models of nonequilibrium Bose gases. The method is based on the av...

The zero-temperature equation of state is analyzed in low-dimensional bosonic systems. We propose to use the concept of energy-dependent s-wave scattering length for obtaining estimations of nonuniversal terms in the energy expansion. We test this approach by making a comparison to exactly solvable one-dimensional problems and find that the generated terms have the correct structure. The applic...

Damping in a dilute Bose gas is investigated using a mean-field approximation which describes the coupled oscillations of condensate and non-condensate atoms in the collisionless regime. Explicit results for both Landau and Beliaev damping rates are given for non-uniform gases. In the case of uniform systems we obtain results for the damping of phonons both at zero and finite temperature. The i...

One-dimensional Bose gases are considered, interacting either through the hardcore potentials or through the contact delta potentials. Interest in these gases gained momentum because of the recent experimental realization of quasi-one-dimensional Bose gases in traps with tightly confined radial motion, achieving the Tonks-Girardeau (TG) regime of strongly interacting atoms. For such gases the F...

Sarang Gopalakrishnan,1,2 Austen Lamacraft,2,3 and Paul M. Goldbart4 1Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA 2Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106, USA 3Department of Physics, University of Virginia, Charlottesville, Virginia 22904, USA 4School of Physics, Georgia Institute of T...

H.E. Nistazakis, Z. Rapti, D.J. Frantzeskakis, P.G. Kevrekidis, P. Sodano , and A. Trombettoni 1 Department of Physics, University of Athens, Panepistimiopolis, Zografos, Athens 15784, Greece 2 Department of Mathematics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801-2975 3 Department of Mathematics and Statistics, University of Massachusetts, Amherst MA 01003-4515, USA 4 Ma...

We review mathematical methods for the treatment of a system of Bose particles with nonuniform density. Common pitfalls are pointed out.

A Lower bound for the density of a Bose gas in Z in the grand canonical ensemble is calculated for general dimension d, and for l(Z) potential interactions. The rigorous formalism of the measure on continuous time random walks, analogous to the Wiener measure, is briefly explained, along with justification of the Feynman-Kac formula using this. These are then used to bound the density, although...