The Spectrum of Dark Radiation as a Probe of Reheating

Understand

After inflation the Universe presumably undergoes a phase of reheating which in effect starts the thermal big bang cosmology.

• However, so far we have very little direct experimental or observational evidence of this important phase of the Universe.
• In this letter, we argue that measuring the spectrum of freely propagating relativistic particles, i.e.
• dark radiation, produced during reheating may provide us with powerful information on the reheating phase.