The primordial lithium problem

Research output: Contribution to journalReview articlepeer-review


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 45-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.

Original languageEnglish (US)
Pages (from-to)47-68
Number of pages22
JournalAnnual Review of Nuclear and Particle Science
StatePublished - 2011


  • Abundances of light elements
  • Big bang nucleosynthesis
  • Dark matter
  • Early universe
  • Extensions of the Standard Model

ASJC Scopus subject areas

  • Nuclear and High Energy Physics


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