Big-bang nucleosynthesis in comparison with observed helium and deuterium abundances: Possibility of a nonstandard model

Abstract

Comparing the latest observed abundances of 4 He and D, we make a χ 2 analysis to see whether it is possible to reconcile primordial nucleosynthesis using up-to-date nuclear data of NACRE II and the mean-life of neutrons. If we adopt the observational data of 4 He by Izotov et al.[1], we find that it is impossible to get reasonable concordance against the standard Big-Bang nucleosynthesis.However, including degenerate neutrinos, we have succeeded in obtaining consistent constraints between the neutrino degeneracy and the baryon-to-photon ratio from detailed comparison of calculated abundances with the observational data of 4 He and D: the baryon-to-photon ratio in units of 10 −10 is found to be in the range 6.02 η 10 6.54 for the specified parameters of neutrino degeneracy.

Fermi–Boltzmann statistics of neutrinos and relativistic effective degrees of freedom in the early universe

“…The large lepton asymmetries are assumed at GeV scale in our scenario. The large lepton asymmetries at MeV scale are almost excluded by the standard BBN cosmology [10,11]. However, the large lepton asymmetries at GeV scale are compatible with current observations [12].…”

“…We note that the unknown masses of the neutrinos are irrelevant in our study. To obtain the chemical potentials of particles, nonlinear simultaneous equations (11), (12) and ( 13) are solved by the Broyden's method [18,19]. From charge neutrality of the universe, we assume q = 0 in Eq.…”

Relativistic effective degrees of freedom and quantum statistics of neutrinos

“…However, in our previous numerical studies, 10,11 we have shown that this relation is not always satisfied with non-vanishing lepton flavor asymmetries in the early universe. [15][16][17][18][19][20][21][22] We complement our previous numerical studies 10,11 by semi-analytical calculations. From Eqs.…”

Effects of quantum fluctuations of metric on the universe

“…Here we are interested in the modifications coming for the quantum fluctuations of metric and take N ν = 3. As well know, the big bang nucleosynthesis (BBN) provides very stringent constraints on the evolution of the early universe [28][29][30][31][32][33][34][35] and has been used to test cosmological models (for example, see references [36][37][38][39][40][41][42][43][44][45][46]). From equations (25) and (39) and taking 0.85 < s < 1.15 [32], we find the parameter α is constrained as −0.141 < α < 0.09 or 1.000025 < α < 1.000046.…”