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Soliton dynamics in the collisions of Bose - Einstein condensates: an analogue of the Josephson effect

The usual mean-field description of trapped atomic Bose - Einstein condensates predicts the existence of solitons in one-dimensional and quasi-one-dimensional confinement. If the net atomic pair interaction is attractive, these solitons appear as coherently propagating matter wavepackets; if it is repulsive, soliton behaviour is seen in the motion of `holes' in the condensate density, the velocity of which is determined by the phase difference between adjoining pieces of condensate, in analogy to the familiar Josephson effect. We explore the properties of these solitons via elementary analytic models and computer simulation, and make specific suggestions for their experimental observation.