Physics Colloquium, 6 March 2001

Tracking the Baryon Density from the Big Bang to the Present

Gary Steigman

The Ohio State University

Primordial nucleosynthesis probes the baryon density when the universe was only a few minutes old. Observations of anisotropy in the cosmic background radiation offer a window on the baryon density several hundred thousand years later. Type Ia supernovae and clusters of galaxies in the present universe provide a complementary measure of the baryon density after several billion years. The excellent agreement among these values represents an impressive confirmation of the standard model of cosmology. There is, however, a hint that these observations are not all in perfect agreement. If the "tension" suggested by the relics from the early universe persists, the standard model of cosmology may need to be modified. I describe how an asymmetry between neutrinos and antineutrinos ("neutrino degeneracy") has the potential for resolving this possible conflict.

3.30 p.m., Smith Laboratory, Room 1005

Refreshments served in Smith 1094 at 3:00 p.m.