Abstract
By assuming the existence of extra-dimensional sterile neutrinos in the big bang nucleosynthesis (BBN) epoch, we investigate the sterile neutrino () effects on the BBN and constrain some parameters associated with the properties. First, for the cosmic expansion rate, we take into account effects of a five-dimensional bulk and intrinsic tension of the brane embedded in the bulk and constrain a key parameter of the extra dimension by using the observational element abundances. Second, effects of the traveling on or off the brane are considered. In this model, the effective mixing angle between a and an active neutrino depends on energy, which may give rise to a resonance effect on the mixing angle. Consequently, the reaction rate of the can be drastically changed during the cosmic evolution. We estimated abundances and temperature of the by solving the rate equation as a function of temperature until the sterile neutrino decoupling. We then find that the relic abundance of the is drastically enhanced by the extra dimension and maximized for a characteristic resonance energy . Finally, some constraints related to the , i.e., mixing angle and mass difference, are discussed in detail with the comparison of our BBN calculations corrected by the extra-dimensional to observational data on light element abundances.
9 More- Received 20 November 2016
- Revised 7 November 2017
DOI:https://doi.org/10.1103/PhysRevD.97.043005
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