BOSE-EINSTEIN CONDENSATION IN TRAPPED ATOMIC GASES

We discuss Bose-Einstein condensation in a trapped atomic gas and anal yze how the sign of the scattering length a and the ratio eta of the i nteraction between particles to the level spacing in the trap influenc e the behavior of the condensate wave function psi(0). We find that fo r a < 0 and eta << 1 it is possible to form a metastable Bose condensa te, with a long characteristic lifetime with respect to contraction an d transitions of particles to excited trap states. For eta >> 1 a nega tive scattering length prevents the formation of the condensate. If a > 0, then an increase of density is accompanied by the evolution of ps i 0 to a comparatively wide quasihomogeneous distribution.