Generation of large-scale magnetic fields from inflation in   teleparallelism
  We explore the generation of large-scale magnetic fields from inflation in teleparallelism, in which the gravitational theory is described by the torsion scalar instead of the scalar curvature in general relativity. In particular, we examine the case that the conformal invariance of the electromagnetic field during inflation is broken by a non-minimal gravitational coupling between the torsion scalar and the electromagnetic field. It is shown that for a power-law type coupling, the magnetic field on 1 Mpc scale with its strength of $\sim 10^{-9}$ G at the present time can be generated. 
Kazuharu Bamba, Chao-Qiang Geng and Ling-Wei Luo
astro-ph.CO gr-qc