Neutrino decoupling in the early Universe

Hannestad, Steen; Madsen, Jes

doi:10.1103/physrevd.52.1764

Cited by 182 publications

(277 citation statements)

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“…The max must be chosen large enough to support the f νi and fν i . We compare the numerically integrated equilibrium energy spectrum to the analytical FD calculation at high temperature and find agreement to a few parts in 10 6 .…”

Section: Binningmentioning

confidence: 97%

“…The work we describe here builds on the many previous studies of the evolution of the neutrino energy distribution functions in the early universe (see Refs. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] and Appendix A). Higher precision in theoretical calculations of neutrino transport and nucleosynthesis in the early universe is warranted by recent and anticipated improvement in the precision of cosmological observations.…”

Section: Introductionmentioning

confidence: 99%

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Neutrino energy transport in weak decoupling and big bang nucleosynthesis

et al. 2016

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We calculate the evolution of the early universe through the epochs of weak decoupling, weak freeze-out and big bang nucleosynthesis (BBN) by simultaneously coupling a full strong, electromagnetic, and weak nuclear reaction network with a multi-energy group Boltzmann neutrino energy transport scheme. The modular structure of our code provides the ability to dissect the relative contributions of each process responsible for evolving the dynamics of the early universe in the absence of neutrino flavor oscillations. Such an approach allows a detailed accounting of the evolution of the νe,νe, νµ,νµ, ντ ,ντ energy distribution functions alongside and self-consistently with the nuclear reactions and entropy/heat generation and flow between the neutrino and photon/electron/positron/baryon plasma components. This calculation reveals nonlinear feedback in the time evolution of neutrino distribution functions and plasma thermodynamic conditions (e.g., electron-positron pair densities), with implications for: the phasing between scale factor and plasma temperature; the neutron-to-proton ratio; light-element abundance histories; and the cosmological parameter N eff . We find that our approach of following the time development of neutrino spectral distortions and concomitant entropy production and extraction from the plasma results in changes in the computed value of the BBN deuterium yield. For example, for particular implementations of quantum corrections in plasma thermodynamics, our calculations show a 0.4% increase in deuterium. These changes are potentially significant in the context of anticipated improvements in obversational and nuclear physics uncertainties.PACS numbers: 95.85.Ry,14.60.Lm,26.35.+c,98.70.Vc

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Section: Binningmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Neutrino energy transport in weak decoupling and big bang nucleosynthesis

et al. 2016

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“…[22]). The difference between ν e and ν µ,τ is related to a greater efficiency of the process e + e − → νν due to the presence of photons and e ± .…”

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confidence: 99%

Varying leptonic chemical potentials and spatial variation of primordial deuterium at high z

Dolgov¹,

Pagel

1999

New Astronomy

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“…Massive neutrinos with masses m ≫ T 0 ∼ 2.4 × 10 −4 eV are non-relativistic at present and therefore contribute to the cosmological matter density [23][24][25] …”

Section: Neutrino Massesmentioning

confidence: 99%

“…Therefore their temperature is lower than the photon temperature by a factor (4/11) 1/3 . This again means that the total neutrino number density is related to the photon number density by n ν = 9 11 n γ (1)Massive neutrinos with masses m ≫ T 0 ∼ 2.4 × 10 −4 eV are non-relativistic at present and therefore contribute to the cosmological matter density [23][24][25]]calculated for a present day photon temperature T 0 = 2.728K. Here, m ν = m 1 + m 2 + m 3 .…”

mentioning

confidence: 99%

Neutrino physics from cosmological observations

Hannestad¹

2003

Nuclear Physics B - Proceedings Supplements

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We review the current status of neutrino cosmology, focusing mainly on the question of the absolute values of neutrino masses and the possibility of a cosmological neutrino lepton asymmetry. Neutrino massesThe absolute value of neutrino masses are very difficult to measure experimentally. On the other hand, mass differences between neutrino mass eigenstates, (m 1 , m 2 , m 3 ), can be measured in neutrino oscillation experiments. Observations of atmospheric neutrinos suggest a squared mass difference of δm 2 ≃ 3 × 10 −3 eV 2 [1,2]. While there are still several viable solutions to the solar neutrino problem the so-called large mixing angle solution gives by far the best fit with δm 2 ≃ 5×10 −5 eV 2 [3,4] (see also contributions by A. Hallin and A. Smirnov in the present volume).In the simplest case where neutrino masses are hierarchical these results suggest that m 1 ∼ 0, m 2 ∼ δm solar , and m 3 ∼ δm atmospheric . If the hierarchy is inverted [5-10] one instead finds m 3 ∼ 0, m 2 ∼ δm atmospheric , and m 1 ∼ δm atmospheric . However, it is also possible that neutrino masses are degenerate [11][12][13][14][15][16][17][18][19][20][21], m 1 ∼ m 2 ∼ m 3 ≫ δm atmospheric , in which case oscillation experiments are not useful for determining the absolute mass scale.Experiments which rely on kinematical effects of the neutrino mass offer the strongest probe of this overall mass scale. Tritium decay measurements have been able to put an upper limit on the electron neutrino mass of 2.2 eV (95% conf.) [22] (see also the contribution by Ch. Weinheimer in the present volume). However, cosmology at present yields an even stronger limit which is also based on the kinematics of neutrino mass.Neutrinos decouple at a temperature of 1-2 MeV in the early universe, shortly before electron-positron annihilation. Therefore their temperature is lower than the photon temperature by a factor (4/11) 1/3 . This again means that the total neutrino number density is related to the photon number density by n ν = 9 11 n γ (1)Massive neutrinos with masses m ≫ T 0 ∼ 2.4 × 10 −4 eV are non-relativistic at present and therefore contribute to the cosmological matter density [23][24][25]]calculated for a present day photon temperature T 0 = 2.728K. Here, m ν = m 1 + m 2 + m 3 . However, because they are so light these neutrinos free stream on a scale of roughly k ≃ 0.03m eV Ω 1/2 m h Mpc −1 [26][27][28]. Below this scale neutrino perturbations are completely erased and therefore the matter power spectrum is suppressed, roughly by ∆P/P ∼ −8Ω ν /Ω m [28].This power spectrum suppression allows for a determination of the neutrino mass from measurements of the matter power spectrum on large scales. This matter spectrum is related to the galaxy correlation spectrum measured in large scale structure (LSS) surveys via the bias parameter, b 2 ≡ P g (k)/P m (k). Such analyses have been performed several times before [29,30], most recently using data from the 2dF galaxy survey [31]. This investigation finds an upper limit of 1.8-2.2 eV for the sum of neutrin...

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Neutrino decoupling in the early Universe

Cited by 182 publications

References 13 publications

Neutrino energy transport in weak decoupling and big bang nucleosynthesis

Neutrino energy transport in weak decoupling and big bang nucleosynthesis

Varying leptonic chemical potentials and spatial variation of primordial deuterium at high z

Neutrino physics from cosmological observations

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