No Crisis for Big Bang Nucleosynthesis

Abstract

Contrary to a recent claim, the inferred primordial abundances of the light elements are quite consistent with the expectations from standard big bang nucleosynthesis when attention is restricted to direct observations rather than results from chemical evolution models. The number of light neutrino (or equivalent particle) species ($N_ν$) can be as high as 4.53 if the nucleon-to-photon ratio ($η$) is at its lower limit of $1.65 \times 10^{-10}$, as constrained by the upper bound on the deuterium abundance in high redshift quasar absorption systems. Alternatively, with $N_ν= 3$, $η$ can be as high as $8.90 \times 10^{-10}$ if the deuterium abundance is bounded from below by its interstellar value.

10 pages LaTeX (uses ReVTeX), including 3 PostScript figures (uses epsf); Full paper available from ftp://ftp.physics.ox.ac.uk/pub/local/users/sarkar/BBNcrisisnot.ps.gz ; Revised to include discussion of new deuterium observations in quasar absorption systems and helium-3 measurement in local interstellar gas, updated Fig 1, no change in conclusions, resubmitted to Phys. Rev. Lett