Reheating and Dark Matter Freeze-in in the Higgs-$R^2$ Inflation Model

Understand

We study the post-inflationary dynamics for reheating and freeze-in dark matter in the Higgs-$R^2$ inflation model.

• Taking the perturbative approach for reheating, we determine the evolution of the temperature for radiation bath produced during reheating and determine the maximum and reheating temperatures of the Universe.
• Adopting a singlet scalar dark matter with a conformal non-minimal coupling and a vanishing Higgs-portal coupling, we discuss the freeze-in production of dark matter both from the non-thermal scattering during reheating and the thermal scattering after reheating.
• We find that thermal scattering is dominant for dark matter production in our model due to the high reheating temperature.