Spin precession in anisotropic cosmologies

TL;DR

This paper investigates how Dirac particle spins precess in anisotropic cosmological models, revealing chaotic behavior in Bianchi-IX universes and potential implications for dark matter through fermion helicity flips.

Contribution

It provides a detailed analysis of spin precession in various anisotropic Bianchi universes, including chaotic effects in Bianchi-IX, and explores implications for early Universe dark matter.

Findings

Spin precession occurs in Bianchi-I universes.

Chaotic spin behavior in Bianchi-IX universes.

Helicity flips may produce sterile dark matter particles.

Abstract

We consider the precession of a Dirac particle spin in some anisotropic Bianchi universes. This effect is present already in the Bianchi-I universe. We discuss in some detail the geodesics and the spin precession for both the Kasner and the Heckmann-Schucking solutions. In the Bianchi-IX universe the spin precession acquires the chaotic character due to the stochasticity of the oscillatory approach to the cosmological singularity. The related helicity flip of fermions in the very early Universe may produce the sterile particles contributing to dark matter.