  We have revisited the spin dynamics in intermediate-energy heavy-ion
collisions based on the improved spin- and isospin-dependent
Boltzmann-Uehling-Uhlenbeck transport model, particularly with the constraint
of rigorous angular momentum conservation incorporated. We have studied the
spin polarization of free nucleons and tritons/$^3$He as well as the spin
alignment of deuterons, and predicted the flow splittings for their different
spin states. We have also demonstrated that the spin-dependent potential may
enhance dissipations and thus have a non-negligible effect on the spin-averaged
transverse flow at low collision energies. When rigorous angular momentum
conservation in each spin-dependent nucleon-nucleon collision is incorporated,
it affects the overall dynamics, the flow, and also the spin polarization,
while the effects of the spin-orbit potential on the spin-related observables
are still appreciable. The well-developed SIBUU model could be further extended
to include hyperons or vector mesons, or used as a hadronic afterburner for
spin-related studies in relativistic heavy-ion collisions, with more inelastic
channels incorporated in the future.
