Triaxial bright solitons in Bose-condensed atomic vapors

The properties of triaxial bright solitons (TBSs) made of attractive Bose-Einstein condensed atoms under transverse anisotropic harmonic confinement are investigated via a variational approach. We show that these metastable TBSs change their shape from cigarlike to disklike by increasing the interatomic 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 begins at a critical value of the interatomic strength. This critical strength is maximal in the isotropic (axially symmetric) case and can be slightly reduced 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.