  We find that the spin-charge motion in a strongly confined two-dimensional
hole gas (2DHG) supports a propagating mode of cubic dispersion apart from the
diffusive mode due to momentum scattering. Propagating modes seem to be a
generic property of systems with spin-orbit coupling. Through a rigorous
Keldysh approach, we obtain the transport equations for the 2DHG, we analyze
the behavior of the hole spin relaxation time, the diffusion coefficients, and
the spin-charge coupled motion.
