We study in a quantitative manner the lepton asymmetry L (net leptons number per photon) in the Universe and its impact on Universe expansion. This is quantified via the standard tool, the effective number of Dirac neutrinos Nνeff . Specifically, we present the dependence of Nνeff on the ambient temperature and the neutrino chemical potential and show the resultant neutrino yields in the cosmic background. We then obtain the dependence of |L| and the baryon-number to lepton-number ratio, B/|L|, on Nνeff . Our results suggest that a value |L| = 0.46 ± 0.06 and B ' (1.33 ± 0.18) × 10−9|L| may be considered.
|Original language||English (US)|
|State||Published - Dec 12 2018|
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