Primordial Light Element Abundances

Understand

After few minutes the Universe evolved through conditions of temperature and density which permitted the first synthesis of astrophysically interesting abundances of D, 3He, 4He and 7Li.

• The relic abundances are sensitive probes of the nucleon density and so are the CMB acoustic oscillations, somewhat 400000 years later, which allow a stringent cross check.
• The CMB high precision estimate of the baryon density by WMAP is currently used as input parameter for standard big bang nucleosynthesis (SBBN) to interpret primordial bundances rather then being directly derived from the observations of light elements as was common use before.
• New atomic physics and identification of systematics lead to an upwards revision of the 4He primordial abundance at Yp=0.2477 +/- 0.0029 (Peimbert et al 2007) removing a major source of tension between SBBN and WMAP.