Particle polarization, spin tensor and the Wigner distribution in relativistic systems

Understand

Particle spin polarization is known to be linked both to rotation (angular momentum) and magnetization of a many particle system.

• However, in the most common formulation of relativistic kinetic theory, the spin degrees of freedom appear only as degeneracy factors multiplying phase-space distributions.
• Thus, it is important to develop theoretical tools that allow to make predictions regarding the spin polarization of particles, which can be directly confronted with experimental data.
• Herein, we discuss a link between the relativistic spin tensor and particle spin polarization, and elucidate the connections between the Wigner function and average polarization.