Dark solitons in the unitary Bose gas

Abstract: We study the dilute and ultracold unitary Bose gas, which is characterized by a universal equation of state due to the diverging s-wave scattering length, under a transverse harmonic confinement. From the hydrodynamic equations of superfluids we derive an effective one-dimensional nonpolynomial Schr\"odinger equation (1D NPSE) for the axial dynamics which, however, takes also into account the transverse dynamics. Finally, by solving the 1D NPSE we obtain meaningful analytical formulas for the dark (gray and black) solitons of the bosonic system.