Dispersive hydrodynamics of nonlinear polarization waves in   two-component Bose-Einstein condensates
  We study one dimensional mixtures of two-component Bose-Einstein condensates in the limit where the intra-species and inter-species interaction constants are very close. Near the mixing-demixing transition the polarization and the density dynamics decouple. We study the nonlinear polarization waves, show that they obey a universal (i.e., parameter free) dynamical description, identify a new type of algebraic soliton, explicitly write simple wave solutions, and study the Gurevich-Pitaevskii problem in this context. 
T. Congy, A. M. Kamchatnov, N. Pavloff
cond-mat.quant-gas nlin.PS