Relativistic hydrodynamics for spin-polarized fluids

Understand

Recent progress in the formulation of relativistic hydrodynamics for particles with spin one-half is reviewed.

• We start with general arguments advising introduction of a tensor spin chemical potential that plays a role of the Lagrange multiplier coupled to the spin angular momentum.
• Then, we turn to a discussion of spin-dependent distribution functions that have been recently proposed to construct a hydrodynamic framework including spin and serve as a tool in phenomenological studies of hadron polarization.
• Distribution functions of this type are subsequently used to construct the equilibrium Wigner functions that are employed in the semi-classical kinetic equation.