Richard H. Cyburt

PRIMORDIAL NUCLEOSYNTHESIS IN THE NEW AGE OF COSMOLOGY: DETERMINING UNCERTAINTIES, EXAMINING CONCORDANCE, AND PROBING NEW PHYSICS

Chapter 1

Overview -- An Introduction to Cosmology -- Primordial Nucleosynthesis -- Cosmic Microwave Background -- Bibliography

Overview

The field of cosmology has recently entered a golden age. An age where a global picture of the universe is crystallizing because of new precision observations that can test the basic framework of the standard cosmological model. With the plethora of new data, it is important to review and test the fundamental theoretical pillars of cosmology. These pillars are the theory of general relativity and the universal expansion, big bang nucleosynthesis (BBN), and the relic cosmic background radiation.

With knowledge of general relativity [4] and the discovery in 1929 by Hubble that the universe was possibly expanding [5], led to the idea that one could extrapolate backwards and conclude that the universe was hotter and denser in the past. This idea became what is currently called the "hot big bang" model of the universe. Almost 20 years later it was realized that at early enough times, the universe would have been hot and dense enough for nuclear fusion to take place. This epoch of primordial nucleosynthesis could explain the large abundances of hydrogen and helium seen in the universe, first explored by Alpher, Bethe and Gamow (1948), Hyashi (1950), and Alpher, Follin and Herman (1953) [6, 7, 8]. The "hot big bang" model also predicted a relic photon background, created when ions recombined with electrons to form neutral atoms (Alpher & Herman, 1949 [9]). In 1965, this uniform 3 Kelvin background was detected by Penzias and Wilson for the first time in the microwave band [10]. This cosmic microwave background (CMB) o®ered supporting evidence for the "hot big bang" model and stimulated further re¯nements in the theory of big bang nucleosynthesis (Peebles, 1966; Wagoner, Fowler & Hoyle, 1967 [11, 12]).

A decade ago, the COBE satellite detected for the first time the 1 : 10⁵ intrinsic temperature fluctuations in the CMB [13]. During the last five years, many more CMB temperature anisotropy measurements have been made (e.g. MAXIMA, BOOMERANG, DASI, CBI, ACBAR [14, 15, 16, 17, 18]). The latest of these observations being from the WMAP satellite, with its first data release in early 2003 [19]. These observations are so precise that we can test and constrain cosmology in a profound and fundamental way.

My thesis compares directly the precision CMB observations with the predictions of the light element abundances from BBN. I discuss the underlying uncertainties, qualifying and quantifying their impact. I then turn the observations around and constrain "non- standard" physics scenarios. In this overview, I will review general cosmology, primordial nucleosynthesis, and the cosmic background radiation.