We study the solitonic Lieb II branch of excitations in one-dimensional Bose-gas in homogeneous and trapped geometry. Using Bethe-ansatz Liebs equations we calculate the effective number of atoms and the effective mass of the excitation. The equations of motion of the excitation are defined by the ratio of these quantities. The frequency of oscillations of the excitation in a harmonic trap is calculated. It changes continuously from its soliton-like value omega_h/sqrt{2} in the high density mean field regime to omega_h in the low density Tonks-Girardeau regime with omega_h the frequency of the harmonic trapping. Particular attention is paid to the effective mass of a soliton with velocity near the speed of sound.
تحميل البحث