Revisit spin effects induced by thermal vorticity

TL;DR

This paper reevaluates spin effects caused by thermal vorticity for spin-1/2 and spin-1 particles, providing new calculations and insights into polarization and spin alignment at different orders of thermal vorticity.

Contribution

It introduces a direct calculation method from spin-dependent distribution functions and extends the analysis to second-order effects for spin-1 particles.

Findings

Polarization for spin-1/2 particles up to first order matches traditional results.

No spin alignment at first order for spin-1 particles, but second-order effects are present.

Additional contributions to spin effects occur when spin direction correlates with particle momentum.

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.