Modified big bang nucleosynthesis with non-standard neutron sources

Understand

During big bang nucleosynthesis, any injection of extra neutrons around the time of the $^7$Be formation, i.e.

• at a temperature of order $T \simeq 50$~keV, can reduce the predicted freeze-out amount of $^7$Be + $^7$Li that otherwise remains in sharp contradiction with the Spite plateau value inferred from the observations of Pop II stars.
• However, the growing confidence in the primordial D/H determinations puts a strong constraint on any such scenario.
• We address this issue in detail, analyzing different temporal patterns of neutron injection, such as decay, annihilation, resonant annihilation, and oscillation between mirror and standard model world neutrons.