Primordial magnetic fields of non-minimal photon-torsion axial coupling origin

TL;DR

This paper investigates how non-minimal photon-torsion axial coupling in Riemann-Cartan spacetime can induce dynamo action and affect photon propagation, offering insights into cosmic magnetic field origins and Lorentz violation effects.

Contribution

It introduces a novel analysis of photon-torsion coupling effects in flat and de Sitter spacetimes, demonstrating dynamo action and Lorentz violation in a quantum electrodynamics framework.

Findings

Photon-torsion coupling induces dynamo action in flat spacetime.

Vacuum polarization alters photon propagation in torsionic de Sitter space.

Torsion inhomogeneities lead to Lorentz violation and massive photon modes.

Abstract

Dynamo action is shown to be induced from homogeneous non-minimal photon-torsion axial coupling in the quantum electrodynamics (QED) framework in Riemann flat spacetime contortion decays. The geometrical optics in Riemann-Cartan spacetime is considering and a plane wave expansion of the electromagnetic vector potential is considered leading to a set of the equations for the ray congruence. Since we are interested mainly on the torsion effects in this first report we just consider the Riemann-flat case composed of the Minkowskian spacetime with torsion. It is also shown that in torsionic de Sitter background the vacuum polarisation does alter the propagation of individual photons, an effect which is absent in Riemannian spaces. It is shown that the cosmological torsion background inhomogeneities induce Lorentz violation and massive photon modes in this QED. Magnetic dynamos in this torsioned spacetime electrodynamics are simpler obtained in Fourier space than the cosmic ones, previously obtained by Bassett et al Phys Rev D, in Friedmann universe. By deriving plasma dispersion for linear electrodynamics in Riemann Cartan spacetime, dynamo action seems to be possible for plasma frequencies in some polarizations. The important cosmic magnetic field problem of breaking conformal flatness is naturally solved here since the photon torsion coupling breaks conformal flatness.