2008/08/21 by Richard H. Cyburt, Brian D. Fields, Keith A. Olive · 4 citations
Physics and Astronomy · #Anisotropy #Astronomical and nuclear sciences #Astrophysics #Big Bang nucleosynthesis #CMB cold spot #Cosmic microwave background #Galactic halo #Galaxy #Halo #Nuclear physics research studies #Nucleosynthesis #Particle physics theoretical and experimental studies #Physics #Population #Quantum mechanics #Redshift #Reionization #Stars #astro-ph
paper · pdf · doi:10.1088/1475-7516/2008/11/012
published as JCAP 0811:012,2008 · 21 pages, 4 figures. Comments welcome
arxiv created 2008/08/21 · openalex publication_date 2008/11/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
The lithium problem arises from the significant discrepancy between the primordial 7 Li abundance as predicted by big bang nucleosynthesis (BBN) theory and the Wilkinson Microwave Anisotropy Probe (WMAP) baryon density, and the pre-Galactic lithium abundance inferred from observations of metal-poor (Population II) stars. This problem has loomed for the past decade, with a persistent discrepancy of a factor of 2–3 in 7 Li / H. Recent developments have sharpened all aspects of the Li problem. Namely: (1) BBN theory predictions have sharpened due to new nuclear data; in particular, the uncertainty on the reaction rate for 3 He(α,γ) 7 Be has reduced to 7.4%, nearly a factor of 2 tighter than previous determinations. (2) The WMAP five-year data set now yields a cosmic baryon density with an uncertainty reduced to 2.7%. (3) Observations of metal-poor stars have tested for systematic effects. With these, we now find that the BBN+WMAP predicts 7 Li / H = (5.24 −0.67 +0.71 ) × 10 −10 . The central value represents an increase by 23%, most of which is due to the upward shift in the 3 He(α,γ) 7 Be rate. More significant is the reduction in the 7 Li / H uncertainty by almost a factor of 2, tracking the reduction in the 3 He(α,γ) 7 Be error bar. These changes exacerbate the Li problem; the discrepancy is now a factor 2.4 or 4.2σ (from globular cluster stars) to 4.3 or 5.3σ (from halo field stars). Possible resolutions to the lithium problem are briefly reviewed, and key experimental and astronomical measurements highlighted.