  We study the transverse spin dynamics of trapped polarized Fermi gases in the
high temperature limit. In the non-interacting collisionless regime, a magnetic
field gradient induces collective spin wave oscillations. In the strongly
interacting collisional regime, the dynamics are governed by spin diffusion.
These two limits have been extensively studied both experimentally and
theoretically, but the crossover between them has received less attention. In
this paper, we use a quantum Boltzmann equation to study transverse spin
dynamics and show how the excitations evolve from dispersive to diffusive in
the high temperature limit. We provide analytical solutions in the two limiting
regimes, which agree well with our numerical results.
