Torsion-induced spin precession

TL;DR

This paper studies how torsion in Einstein-Cartan theory causes spin precession of particles in a flat FRW universe, revealing different precession behaviors for spinning particles with transverse spin and charged particles in magnetic fields.

Contribution

It demonstrates the effects of torsion on spin precession in a cosmological setting, highlighting differences from magnetic field-induced precession.

Findings

Torsion causes precession of particles with transverse spin components.

Charged particles in magnetic fields precess differently in torsion-free spacetime.

Spin precession behaviors depend on the presence of torsion and electromagnetic fields.

Abstract

We investigate the motion of a spinning test particle in a spatially-flat FRW-type space-time in the framework of the Einstein-Cartan theory. The space-time has a torsion arising from a spinning fluid filling the space-time. We show that for spinning particles with nonzero transverse spin components, the torsion induces a precession of particle spin around the direction of the fluid spin. We also show that a charged spinning particle moving in a torsion-less spatially-flat FRW space-time in the presence of a uniform magnetic field undergoes a precession of a different character.