Measuring the baryon content of the universe: BBN vs CMB

Abstract

The relic abundance of baryons - the only form of stable matter whose existence we are certain of - is a crucial parameter for many cosmological processes, as well as material evidence that there is new physics beyond the Standard Model. We discuss recent determinations of the cosmological baryon density from analysis of the abundances of light elements synthesised at the end of ``the first three minutes'', and from the observed temperature anisotropies imprinted on small angular-scales in the cosmic microwave background when the universe was about 100,000 yr old.

14 pages, 5 figures (LaTeX); Invited talk at the XIII Recontres de Blois "Frontiers of the Universe", 17-23 June 2001