Lepton epoch

In physical cosmology, the lepton epoch was the period in the evolution of the early universe in which the leptons dominated the mass of the Universe. It started roughly 1 second after the Big Bang, after the majority of hadrons and anti-hadrons annihilated each other at the end of the hadron epoch.[1] During the lepton epoch the temperature of the Universe was still high enough to create neutrino and electron-positron pairs. Approximately 10 seconds after the Big Bang the temperature of the universe had fallen to the point where electron-positron pairs were gradually annihilated.[2] A small residue of electrons needed to charge-neutralize the Universe remained along with free streaming neutrinos: an important aspect of this epoch is the neutrino decoupling.[3] The Big Bang nucleosynthesis epoch follows overlapping with the photon epoch.[4][5]

See alsoEdit


  1. ^ Fromerth, M.J.; Kuznetsova, I.; Labun, L.; Letessier, J.; Rafelski, J. (2012). "From Quark-Gluon Universe to Neutrino Decoupling: 200 < T < 2MeV". Acta Physica Polonica B. 43 (12): 2261. doi:10.5506/APhysPolB.43.2261. ISSN 0587-4254.
  2. ^ "Thermal history of the Universe and early growth of density fluctuations" (PDF). Guinevere Kauffmann. Max Planck Institute for Astrophysics. Retrieved 2016-01-06.
  3. ^ Birrell, Jeremiah; Yang, Cheng Tao; Rafelski, Johann (2015). "Relic neutrino freeze-out: Dependence on natural constants". Nuclear Physics B. 890: 481–517. doi:10.1016/j.nuclphysb.2014.11.020.
  4. ^ "First few minutes". Eric Chaisson. Havard Smithsonian Center for Astrophysics. Retrieved 2016-01-06.
  5. ^ "Timeline of the Big Bang". The physics of the Universe. Retrieved 2016-01-06.