Gravitational particle production in bouncing cosmologies

© 2015 IOP Publishing Ltd and Sissa Medialab srl . It is argued that the Universe reheating in bouncing cosmologies could be explained via gravitational particle production, as due to a sudden phase transition in the contracting regime. To this end, it is shown that, in the context of Loop Quantum Cosmology, gravitational production of massive particles conformally coupled with gravity in a matter-ekpyrotic bouncing Universe, where the sudden phase transition occurs in the contracting regime, yields a reheating temperature which is in good agreement with cosmological observations.