The dynamics that follow the end of inflation are a potentially rich probe of physics beyond the Standard Model. During this period of reheating, the primordial dark matter abundance could have been produced from the interaction of the inflaton decay products, which attain thermal equilibrium quickly after being produced.
Together with K. Olive, M. Peloso and Y. Mambrini, we have explored the dependence of the primordial dark matter abundance on the maximum temperature ever reached by the universe, well before the end of reheating. Using a model in which dark matter is weakly interacting and never reaches thermal equilibrium (the so-called freeze-in mechanism), we have found that the final abundance is insensitive to this maximum temperature if the production cross section is a less steeper function of temperature than , as dilution due to the continuing decay of the inflaton dominates over production. However, in the case of very high-scale supersymmetry, for which the gravitino is the dark matter particle and , a non-trivial dependence on is found.
The paper in question:
M. A. G. Garcia, Y. Mambrini, K. A. Olive and M. Peloso, Enhancement of the Dark Matter Abundance Before Reheating: Applications to Gravitino Dark Matter, arXiv:1709.01549 [hep-ph].