Recent experiments in a mixture of two hyperfine states of trapped Bose gases show behavior analogous to a spin-$\frac{1}{2}$ system, including transverse spin waves and other familiar Leggett-Rice-type effects. We have derived the kinetic equations applicable to these systems, including the spin dependence of interparticle interactions in the collision integral, and have solved for spin-wave frequencies and longitudinal and transverse diffusion constants in the Boltzmann limit. We find that, while the transverse and longitudinal collision times for trapped Fermi gases are identical, the Bose gas shows unusual diffusion anisotropy in both dipole and quadrupole modes. Moreover, the lack of spin isotropy in the interactions leads to the nonconservation of transverse spin, which in turn has significant effects on the hydrodynamic modes.

• Received 23 June 2006

DOI:https://doi.org/10.1103/PhysRevA.74.043607