Effects of primordial magnetic fields on CMB
  The origin of large-scale magnetic fields is an unsolved problem in
cosmology. In order to overcome, a possible scenario comes from the idea that
these fields emerged from a small primordial magnetic field (PMF), produced in
the early universe. This field could lead to the observed large-scales magnetic
fields but also, would have left an imprint on the cosmic microwave background
(CMB). In this work we summarize some statistical properties of this PMFs on
the FLRW background. Then, we show the resulting PMF power spectrum using
cosmological perturbation theory and some effects of PMFs on the CMB
anisotropies.
