Lepton number and expansion of the Universe

Cheng Tao Yang, Jeremiah Birrell, Johann Rafelski

Research output: Contribution to journalArticlepeer-review


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) × 109|L| may be considered.

Original languageEnglish (US)
JournalUnknown Journal
StatePublished - Dec 12 2018

ASJC Scopus subject areas

  • General

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