Production of photons in a bouncing universe
  Using a new non-singular solution,it is shown that the production of photons in dilaton electrodynamics in a cosmological setting is increased if the effect of matter creation on the geometry is taken into account. This increment may be related to the problem of the origin of magnetic fields in the universe. 
J.M. Salim, S.E. Perez Bergliaffa, and N. Souza