Preheating a bouncing universe
  Preheating describes the stage of rapidly depositing the energy of cosmological scalar field into excitations of other light fields. This stage is characterized by exponential particle production due to the parametric resonance. We study this process in the frame of matter bounce cosmology. Our results show that the preheating process in bouncing cosmology is even more efficient than that in inflationary cosmology. In the limit of weak coupling, the period of preheating is doubled. For the case of normal coupling, the back-reaction of light fields can lead to thermalization before the bouncing point. The scenario of matter bounce curvaton could be tightly constrained due to a large coupling coefficient if the curvaton field is expected to preheat the universe directly. However, this concern can be greatly relaxed through the process of geometric preheating. 
Yi-Fu Cai, Robert Brandenberger, Xinmin Zhang
hep-th astro-ph.CO gr-qc hep-ph