Constraints on Lepton Asymmetry from Nucleosynthesis in a Linearly Coasting Cosmology

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 ($ξ_e$) 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, $η_B$=(3.927$\pm$0.292)10$^{-9}$, corresponding to a baryonic matter density, $Ω_B$=0.263$\pm$ 0.026 and $ξ_e$=-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.

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