Limits on Brane-World and Particle Dark Radiation from Big Bang Nucleosynthesis and the CMB

Understand

The term dark radiation is used both to describe a noninteracting neutrino species and as a correction to the Friedmann Equation in the simplest five-dimensional RS-II brane-world cosmology.

• In this paper we consider the constraints on both meanings of dark radiation based upon the newest results for light-element nuclear reaction rates, observed light-element abundances and the power spectrum of the Cosmic Microwave Background (CMB).
• Adding dark radiation during big bang nucleosynthesis (BBN) alters the Friedmann expansion rate causing the nuclear reactions to freeze out at a different temperature.
• This changes the final light element abundances at the end of BBN.