Constraints on Lepton Asymmetry from Nucleosynthesis in a Linearly Coasting Cosmology

Abstract

We study the effect of neutrino degeneracy on primordial nucleosynthesis in a universe in which the cosmological scale factor evolves linearly with time. The degeneracy parameter of electron type neutrinos (${\xi }_e$) determines the $n/p$ (neutron to proton) ratio, which in turn determines the abundance of ${}^4$He in a manner quite distinct from the Standard Scenario. The observed abundances of ${}^4$He, ${\mathrm{Y}}_P$=0.254$\pm$0.003, and the minimum metallicity that is essential for fragmentation and cooling processes in star forming prestellar gas clouds (Z = Z${}_{cr}$ = 10${}^{-6}$Z${}_{\odot }$), constrain the baryon to photon ratio, ${\eta }_B$=(3.927$\pm$0.292)10${}^{-9}$, corresponding to a baryonic matter density, ${\Omega }_B$=0.263$\pm$ 0.026 and ${\xi }_e$=-2.165$\pm$0.171. This closes the dynamic mass estimates of matter in the universe by baryons alone. Useful byproducts are the threshold X(CNO) abundances required to trigger the CNO cycle in the observed low metallicity stars in the universe.

18 Pages, 9 Figures. Matches published version

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• Matter creation and primordial CMB Spectrum in the inflationless Milne-like cosmologies
• Gauss-Bonnet Gravity in $D=4$ Without Gauss-Bonnet Coupling to Matter - Cosmological Implications
• Equilibrium Thermodynamics and Neutrino Decoupling in Quasi-Metric Cosmology