ar X iv : a st ro - p h / 97 04 04 0 v 1 3 A pr 1 99 7 Inflationary Cosmology

Inflation is a bold and expansive extension of the Standard Cosmology. It holds the promise to extend our understanding of the Universe to within 10 −32 sec of the big bang and answer most of the pressing questions in cosmology. Its boldest assertion is that all the structure observed in the Universe today arose from quantum-mechanical fluctuations on subatomic scales. A flood of cosmological observations and laboratory experiments are testing inflation and within five years we should know whether inflation is to become part of a new standard cosmology. The value of the Hubble constant has changed by about a factor of ten since Edwin Hubble's pioneering measurements. The context in which we view the Universe has changed even more profoundly. Until 1964 cosmology was mostly concerned with cos-mography; the spirit of this period was perhaps best captured by Sandage, " the quest for two numbers (H 0 and q 0). " The discovery of the Cosmic Background Radiation (CBR) led to the establishment of a physical foundation for the expanding Universe – the hot big-bang cosmology. The 1970s saw this model become firmly established as the Standard Cosmology. Igor Novikov played an important role in this enterprise, and with Zel'dovich wrote one of the first reviews of the Standard Cosmology (Novikov & Zel'dovich 1967) as well as a comprehensive and authoritative summary of it in Volume 2 of Relativistic Astrophysics (Structure and Evolution of the Universe) (Zel'dovich & Novikov 1983). The hot big-bang cosmology is a remarkable achievement. It provides a reliable account of the Universe from about 10 −2 sec to the present (Peebles et al. 1991; Turner 1993a). Further, the hot big-bang model together with modern ideas in particle physics — the Standard Model, supersymmetry, grand unification, and superstring theory — provides a framework for sensible speculation all the way back to the Planck epoch, and perhaps even earlier. Here too, Novikov was one of the pioneering figures in the study of the earliest moments (Novikov & Zel'dovich 1973; Zel'dovich & Novikov 1983). Building upon the Standard Cosmology, in the 1980s cosmologists and particle physicists began an ambitious program to root the hot big-bang model in fundamental physics and to address a deeper set of questions. What is the nature of the ubiquitous dark matter that is the dominant component of the mass density? Why does the Universe contain only matter? What is the origin of the …