Bright solitary waves of trapped atomic Bose–Einstein condensates

Motivated by recent experimental observations, we study theoretically multiple bright solitary waves of trapped Bose–Einstein condensates. Through variational and numerical analyses, we determine the threshold for collapse of these states. Under ππ-phase differences between adjacent waves, we show that the experimental states lie consistently at the threshold for collapse, where the corresponding in-phase states are highly unstable. Following the observation of two long-lived solitary waves in a trap, we perform detailed three-dimensional simulations which confirm that in-phase waves undergo collapse while a ππ-phase difference preserves the long-lived dynamics and gives excellent quantitative agreement with experiment. Furthermore, intermediate phase differences lead to the growth of population asymmetries between the waves, which ultimately triggers collapse.