• 21-cm
• cosmology
• dark matter
• scattering

In this thesis project we propose a Dark Matter model that can affect the thermal
history of cosmic hydrogen after the CMB decoupling leaving an imprint on
cosmological 21-cm signal.
In particular, in 2018, EDGES claimed to have observed a 21-cm signal is in absorption, extending from redshift 20 to 15 and it has an amplitude of 500±200mK at 99% CL. The 500 value of the plateau, centered at a frequency
of 78MHz, translating to a redshift of 17.2, is quite surprising because is 3.8σ
away from the prediction of standard cosmology around 230mK.
One of the possible way to get a more pronounced signal in absorption is
to cool the baryionic gas even more than the very well predicted adiabatic
cooling from standard cosmology. More specifically, it was almost immediately
proposed that DM-baryon collisions could provide an efficient mechanism to cool
the hydrogen gas. The most relevant model, which is still not excluded, consists
in a small fraction of milli-charged DM (mDM), which induce a long-range force
with ordinary matter.
Elastic and inelastic mDM-H scattering may change considerably the temperature of
the IGM and change the 21-cm signal accordingly. This work provides numerical solutions for the elastic process and compares the different regimes: Born, resonant and classical regime.