Physics Division Seminars bring us speakers on a variety of physics related subjects. Usually these are held in the Building 6008 large Conference Room, at 3:00 pm on the chosen day, but times and locations may vary. For more information, contact our seminar chairman,
Tel (Office): (865) 574-6124 (FAX): (865) 574-1268
The earliest time in the history of the universe that is clearly probed by observations is the period from about one second to about five minutes after the big bang, when the initial chemical composition of the universe was determined in the process known as big-bang nucleosynthesis (BBN). This was a much simpler time than today, so the physical processes that produced measureable amounts of only hydrogen, helium, and lithium can be easily modeled. By studying the isotopic compositions of the light elements and comparing against the model, we learn about both the overall structure of the universe and the fundamental particles that populate it. I will review the theory and observational evidence regarding BBN, as well as their relation to other cosmological measurements. I will then discuss recent results concerning elementary-particle properties and the surprisingly loose limits on large-scale inhomogeneities in the primordial distribution of matter. Finally, I will examine some lingering difficulties with BBN. Throughout the discussion I will emphasize the important role of the physics of light nuclei in formulating BBN as a high-precision theory.