Speaker
Description
The thermal history of the Universe before Big Bang Nucleosynthesis (BBN) remains one of the least constrained epochs in cosmology, owing to the absence of direct observational probes. Reheating, which bridges the end of inflation and the onset of the radiation-dominated era, plays a central role in shaping the thermal history before BBN, yet its dynamics remain poorly understood. Since dark matter (DM) production depends sensitively on the thermal history prior to BBN, it can serve as a probe of reheating and, more broadly, of the pre-BBN Universe. Using representative examples such as sterile neutrinos, axions and ALPs, I will show how DM production and possible observational signatures can extract information about reheating dynamics and key parameters. DM is therefore not only a major cosmic component, but also a record of the cosmological history that shaped its production.