CfA Colloquium: May 15, 2003

Speaker: Brian Fields (U. Illinois)

Title: Primordial Nucleosynthesis in Light of WMAP

Abstract: Big bang nucleosynthesis (BBN) describes the production of the lightest elements in the first minutes of cosmic time. I will review the physics of cosmological element production, and the observations of the primordial element abundances. The comparison between theory and observation has heretofore provided our earliest probe of the universe, and given the best measure of the cosmic baryon content. However, recent measurements of the cosmic microwave background (CMB) anisotropies by the Wilkinson Microwave Anisotropy Probe yield an independent and precise measure of the baryon density. The confrontation between the BBN and CMB "baryometers" poses a new and stringent test of the standard cosmology. The status of this test will be discussed, along with the prospects for turning the problem around: using the CMB to fix the baryon density, which transforms BBN into a more powerful probe of early universe physics, and of galactic nucleosynthesis processes.