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