The ideal relativistic spinning gas: polarization and spectra

TL;DR

This paper analyzes the properties of an ideal relativistic spinning gas at thermodynamical equilibrium, deriving analytical expressions for momentum spectra and polarization, revealing anisotropic emission and complex polarization behavior.

Contribution

It provides the first analytical formulas for spectra and polarization of a relativistic spinning gas with massive particles, highlighting new anisotropic and polarization effects.

Findings

Angular momentum causes anisotropic momentum spectra.

Polarization vector is not aligned with total angular momentum.

Particles emitted orthogonally to J have higher average momentum.

Abstract

We study the physics of the ideal relativistic rotating gas at thermodynamical equilibrium and provide analytical expressions of the momentum spectra and polarization vector for the case of massive particles with spin 1/2 and 1. We show that the finite angular momentum J entails an anisotropy in momentum spectra, with particles emitted orthogonally to J having, on average, a larger momentum than along its direction. Unlike in the non-relativistic case, the proper polarization vector turns out not to be aligned with the total angular momentum with a non-trivial momentum dependence.