Metric-torsion preheating: cosmic dynamo mechanism?
  Earlier Bassett et al [Phys Rev D 63 (2001) 023506] investigated the amplification of large scale magnetic fields during preheating and inflation in several different models. They argued that in the presence of conductivity resonance effect is weakened. From a dynamo equation in spacetimes endowed with torsion recently derived by Garcia de Andrade [Phys Lett B 711: 143 (2012)] it is shown that a in a universe with pure torsion in Minkowski spacetime the cosmological magnetic field is enhanced by ohmic or non-conductivity effect, which shows that the metric-torsion effects is worth while of being studied. In this paper we investigated the metric-torsion preheating perturbation, which leads to the seed cosmological magnetic field in the universe with torsion is of the order of $B_{seed}\sim{10^{-37}Gauss}$ which is several orders of magnitude weaker than the decoupling value obtained from pure metric preheating of $10^{-15}Gauss$. Despite of the weakness of the magnetic field this seed field may seed the galactic dynamo. 
L C Garcia de Andrade (dept of theoretical physics, uerj, rio de   janeiro, RJ, Brasil)
astro-ph.GA