Solitary waves in Bose-condensed atomic clouds with attractive interactions

We discuss the propagation of compact wave packets in a three-dimensional B ose condensate of atoms with attractive interactions, in a regime where the longitudinal coherence length is much larger than the transverse dimension s. Harmonic transverse confinement is assumed and treated dynamically by a method proposed by Jackson, Kavoulakis and Pethick (Phys. Rev. A 58 (1998) 2417). Propagation of solitary waves occurs in this regime in the absence o f axial confinement and indeed, starting from a generic initial profile, se lf-organization of compact wave packets of matter can take place above a th reshold. We also discuss the role of a weak axial confinement and illustrat e it with numerical calculations on a condensate of Li-7 atoms. (C) 2000 El sevier Science B.V. All rights reserved.