Triaxial Bright Solitons in Bose-Condensed Atomic Vapors

The properties of triaxial bright solitons (TBSs) made of attractive BoseEinstein condensed atoms under transverse anisotropic harmonic confinement are investigated by using a variational approach. We show that these metastable TBSs change their shape from cigar-like to disc-like by increasing the inter-atomic strength. Moreover, we find that the collective oscillations of a TBS strongly depend on the anisotropy parameter of the external potential. We calculate in detail the properties of TBS close to the collapse, which sets up at a critical value of the inter-atomic strength. This critical strength is maximal in the isotropic (axially symmetric) case and slightly reduces by increasing the anisotropy. Finally, we investigate the formation of multiple TBSs via modulational instability induced by a sudden change of the scattering length from positive to negative.