Stochastic Variational Method for Atomic Gases

We have applied the stochastic variational method [1] to trapped cold gases and calculated energies, densities, correlation functions and condensate fractions as function of scattering length and particle number [2]. We also investigated the $N$-body Efimov effect for systems with $N=3, 4, 5, 6,$ and $7$ bosons at infinite scattering length and obtained the characteristic exponential scaling factors for the energies and densities [3]. We have also compared the finite-range three-body model with the zero-range model [4] and determined the validity region of, and the effective range corrections to, the latter.\newline [1] H.H. Sorensen, D.V. Fedorov and A.S. Jensen, AIP Conference Proc. {\bf 777} (2005) 12; K. Varga and Y. Suzuki, Comput. Phys. Commun. {\bf 106} (1997) 157.\newline [2] M. Th{\o}gersen, D.V. Fedorov and A.S. Jensen, Europhys. Lett. {\bf 79} (2007) 40002.\newline [3] M. Th{\o}gersen, D.V. Fedorov and A.S. Jensen, submitted to Europhys. Lett.\newline [4] E. Braaten and H.-W. Hammer, Phys. Rep. {\bf 428} (2006) 259; T. Kraemer et al., Nature {\bf 440} (2006) 315.