Big bang nucleosynthesis (BBN) theory, together with the precise WMAP cosmic baryon density, makes tight predictions for the abundances of the lightest elements. Deuterium and 4He measurements agree well with expectations, but 7Li observations lie below the BBN+WMAP prediction by a factor of three to four. This 4-5-σ mismatch constitutes the so-called cosmic lithium problem; disparate solutions are possible. First, astrophysical systematics in the observations could exist but are increasingly constrained. Second, nuclear physics experiments provide a wealth of well-measured cross-section data, but 7Be destruction could be enhanced by unknown or poorly measured resonances. Third, physics beyond the Standard Model could alter the 7Li abundance, although deuterium and 4He must remain unperturbed. In this review, we discuss such scenarios, highlighting decaying supersymmetric particles and time-varying fundamental constants. Present and planned experiments could reveal which (if any) of these proposed solutions is correct.
Annual Review of Nuclear and Particle Science
- Pub Date:
- November 2011
- Astrophysics - Cosmology and Extragalactic Astrophysics;
- High Energy Physics - Phenomenology;
- Nuclear Theory
- 29 pages, 7 figures. Per Annual Reviews policy, this is the original submitted draft. Posted with permission from the Annual Review of Nuclear and Particle Science, Volume 61. Annual Reviews, http://www.annualreviews.org . Final published version at http://www.annualreviews.org/doi/abs/10.1146/annurev-nucl-102010-130445