Polarization (cosmology)

For other uses, see Polarization.

According to the standard Big Bang theory, the early universe was sufficiently hot for all the matter in it to be fully ionised. Under these conditions, electromagnetic radiation was scattered very efficiently by matter, and this scattering kept the early universe in a state of thermal equilibrium.[1]

In physical cosmology, following the quark epoch[2] (when the fundamental interactions of gravitation, electromagnetism, the strong interaction and the weak interaction had taken their present forms, but the temperature of the universe was still too high to allow quarks to bind together to form hadrons[2]) was the hadron epoch in which most of the hadrons and anti-hadrons were eliminated in annihilation reactions, leaving a small residue of hadrons and a Universe dominated by photons, neutrinos and electron-positron pairs called the lepton epoch during which the neutrino decoupling took place.[3] Thereafter the Big Bang nucleosynthesis epoch followed, overlapping with the photon epoch[4][5] where once recombination was virtually complete, photons ceased to scatter at all and began to propagate freely through the Universe, suffering only the effects of the cosmological redshift.[1]

These two verified instances of decoupling since the Big Bang - namely, neutrino decoupling and photon decoupling led to the cosmic neutrino background and cosmic microwave background respectively, in that sequence. However, the neutrinos from neutrino decoupling event have a very low energy, around 10−10 times smaller than is possible with present-day direct detection.[6] Hence, Neutrino decoupling#Indirect evidence from phase changes to the Cosmic Microwave Background (CMB) theorises that the decoupled neutrinos should have had a very slight effect on the phase of the various CMB fluctuations.[6]

  1. ^ a b "LAST SCATTERING SURFACE". ned.ipac.caltech.edu. Retrieved 2024-10-11.
  2. ^ a b Rafelski, Johann (October–November 2013). "Connecting QGP-Heavy Ion Physics to the Early Universe". Nuclear Physics B: Proceedings Supplements. 243–244: 155–162. arXiv:1306.2471. Bibcode:2013NuPhS.243..155R. doi:10.1016/j.nuclphysbps.2013.09.017. S2CID 118460277 – via ResearchGate.
  3. ^ Birrell, Jeremiah; Yang, Cheng Tao; Rafelski, Johann (2015). "Relic neutrino freeze-out: Dependence on natural constants". Nuclear Physics B. 890: 481–517. arXiv:1406.1759. Bibcode:2015NuPhB.890..481B. doi:10.1016/j.nuclphysb.2014.11.020.
  4. ^ "First few minutes". Eric Chaisson. Harvard Smithsonian Center for Astrophysics. Retrieved 2016-01-06.
  5. ^ "Timeline of the Big Bang". The physics of the Universe. Retrieved 2016-01-06.
  6. ^ a b Cosmic Neutrinos Detected, Confirming The Big Bang's Last Great Prediction - Forbes coverage of original paper: Follin, Brent; Knox, Lloyd; Millea, Marius; Pan, Zhen (2015-08-26). "First Detection of the Acoustic Oscillation Phase Shift Expected from the Cosmic Neutrino Background". Physical Review Letters. 115 (9): 091301. arXiv:1503.07863. Bibcode:2015PhRvL.115i1301F. doi:10.1103/physrevlett.115.091301. ISSN 0031-9007. PMID 26371637. S2CID 24763212.