#### IMSc Webinar

#### Reheating in two-sector cosmology

#### Pranjal Ralegankar

##### University of Illinois, Urbana-Champaign

*We analyze reheating scenarios where a hidden sector is populated during reheating
along with the sector containing the Standard Model. We numerically solve the Boltzmann
equations describing perturbative reheating of the two sectors, including the full dependence
on quantum statistics, and study how quantum statistical effects during reheating as well
as the non-equilibrium inflaton-mediated energy transfer between the two sectors affects the
temperature evolution of the two radiation baths. We obtain new power laws describing the
temperature evolution of fermions and bosons when quantum statistics are important during
reheating. We show that inflaton-mediated scattering is generically most important at
radiation temperatures T ∼ Mφ/4, and build on this observation to obtain analytic estimates for
the temperature asymmetry produced by asymmetric reheating. We find that for reheating
temperatures Trh << Mφ/4, classical perturbative reheating provides an excellent approximation
to the final temperature asymmetry, while for Trh >> Mφ/4, inflaton-mediated scattering
dominates the population of the colder sector and thus the final temperature asymmetry. We
additionally present new techniques to calculate energy transfer rates between two relativistic
species at different temperatures.
Reference: arxiv.org/pdf/1906.02755.pdf*

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