%0 Journal Article %T Primordial Magnetic Fields from the Post-Inflationary Universe %A Takeshi Kobayashi %J Physics %D 2014 %I arXiv %R 10.1088/1475-7516/2014/05/040 %X We explore cosmological magnetogenesis in the post-inflationary universe, when the inflaton oscillates around its potential minimum and the universe is effectively dominated by cold matter. During this epoch prior to reheating, large-scale magnetic fields can be significantly produced by the cosmological background. By considering magnetogenesis both during and after inflation, we demonstrate that magnetic fields stronger than 10^{-15} G can be generated on Mpc scales without having strong couplings in the theory, or producing too large electric fields that would dominate the universe. %U http://arxiv.org/abs/1403.5168v2