Migration of particles in an inhomogeneous medium

Relic neutrinos: Antineutrinos of primordial nucleosynthesis

“…The non-thermal spectra. Doublet of narrow cosmological neutrino lines due to decays of 7 Be [25] and the non-equilibrium neutrino distortion (∆f ≡ f − f0) of the CνB high-energy tail caused by e ± -annihilation [6,7] (dotted violet curves). The non-thermal antineutrino spectra formed by decays of neutronsν(n) (red curve) and tritonsν(t) (crimson curve) which have been calculated in this work.…”

“…• The first of these phenomena is the non-equilibrium neutrino distortion of the CνB high-energy tail caused by e ± -annihilation occurred at the beginning of primordial nucleosynthesis at T 1 MeV (for more details see [6][7][8][9][10]).…”

“…The theory of primordial nucleosynthesis give us the relation between the relic neutrino and photon temperatures, T ν = (4/11) 1/3 T γ , arising from electron-positron annihilation. Given this relation and the current value of T γ0 = 2.725 ± 0.001 K [5], we have the present temperature of relic neutrinos to be T ν0 ≈ 1.945 K. However, at the same time the electron-positron annihilation leads to the heating of neutrinos and forms the non-thermal distortion of the neutrino spectrum [6][7][8][9][10], therefore strictly speaking T ν0 is not defined. In addition to the relic neutrinos it should be mentioned that there are other neutrino backgrounds at high energies (ε 1 MeV) which could be called "cosmological" as well: the diffuse supernova neutrino background [11], the active galactic nuclei (AGN) background and cosmogenic (GZK) neutrinos arising from interactions of ultra-energetic protons with the CMB photons (for more details see e.g.…”