Revisit spin effects induced by thermal vorticity

Abstract: We revisit the spin effects induced by thermal vorticity by calculating them directly from the spin-dependent distribution functions. For the spin-1/2 particles, we give the polarization up to the first order of thermal vorticity and compare it with the usual result calculated from the spin vector. For the spin-1 particles, we find that all the non-diagonal elements vanish and there is no spin alignment up the first order of thermal vortcity. We present the spin alignment at second-order contribution from thermal vorticity. We also find that the spin effects for both Dirac and vector particles will receive extra contribution when the spin direction is associated with the particle's momentum.