Polarization of spin-1/2 particles with effective spacetime dependent masses

TL;DR

This paper develops a theoretical framework to analyze how spacetime-dependent masses influence spin polarization in spin-1/2 particles, revealing that mass gradients can generate spin polarization effects, especially in non-boost-invariant systems.

Contribution

The authors reformulate the semiclassical Wigner function approach to directly relate spin tensor dynamics with effective spacetime-dependent masses, highlighting the role of mass gradients as sources of spin polarization.

Findings

Mass gradients act as sources of spin polarization.

Spin density depends non-trivially on mass in non-boost-invariant systems.

Spin polarization effects may be linked to chiral restoration phenomena.

Abstract

Semiclassical expansion of the Wigner function for spin-1/2 fermions having an effective spacetime-dependent mass is used to analyze spin-polarization effects. The existing framework is reformulated to obtain a differential equation directly connecting the particle spin tensor with the effective mass. It reflects the conservation of the total angular momentum in a system. In general, we find that the gradients of mass act as a source of the spin polarization. Although this effect is absent for simple boost-invariant dynamics, an extension to non-boost-invariant systems displays a non-trivial dependence of the spin density on the mass indicating that the spin polarization effects may be intertwined with the phenomenon of chiral restoration.