Speaker
Description
The reheating epoch following inflation sets the initial conditions
for the subsequent thermal history of the Universe, but remains
largely unconstrained prior to Big Bang nucleosynthesis. In many
extensions of the Standard Model, the inflaton may decay
simultaneously into visible and hidden sectors, leading to
non-standard cosmological histories. One possibility is an
asymmetric reheating in which unequal amounts of energy are
deposited in the visible and dark sectors, resulting in different
temperatures and potential entropy exchange between them. In this
talk, I will study asymmetric reheating in a simple and instructive
hidden sector framework: dark QED, consisting of a Dirac fermion
dark matter candidate charged under a dark U(1)′ gauge symmetry and
a massive dark photon coupled to the visible sector via kinetic
mixing. A central part of the discussion will be the thermalisation
of dark QED after inflation, during reheating. I will focus on
thermalization in the weak-coupling and initially under-occupied
regime. I will then discuss the evolution of the temperature ratio
during the reheating process. I will finally explore the
implications for thermal dark matter production, highlighting viable
regions of parameter space where dark matter is thermalized at a
temperature different from that of the Standard Model.
| Other topic / keywords: | Reheating, Hidden Sector, Dark QED |
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