Bulletin of the American Physical Society
2006 APS April Meeting
Saturday–Tuesday, April 22–25, 2006; Dallas, TX
Session C5: Cosmology II |
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Sponsoring Units: DAP FHP Chair: Virginia Trimble, University of California, Irvine Room: Hyatt Regency Dallas Pegasus B |
Saturday, April 22, 2006 1:30PM - 2:06PM |
C5.00001: Before the Microwave Background: Early Big Bang Cosmology (The J. Robert Oppenheimer Lecture) Invited Speaker: Finite-age (or big-bang) cosmological models can be traced back to G. Lema\^{\i}tre's relativistic model of 1931 (or even earlier, to A. Friedmann in 1922). However, the big bang concept does not exclusively belong to the class of relativistic models, and in the 1930s it was often associated with E.A. Milne's very different, so-called kinematic cosmology. But it was only with G. Gamow's research program in the late 1940s that the big-bang scenario became widely known and turned into a nuclear-physical theory of the early universe. How does the theory of Gamow and his collaborators R. Alpher and R. Herman compare with Lema\^{\i}tre's earlier ideas of a ``primeval atom''? And with the post-1965 version of big bang cosmology? The strange fate of the Gamow-Alpher-Herman hot big bang theory can only be understood if taking into account that relativistic evolution cosmology faced stiff competition throughout the 1950s from the steady-state theory of F. Hoyle and others. [Preview Abstract] |
Saturday, April 22, 2006 2:06PM - 2:42PM |
C5.00002: The New Standard Cosmology Invited Speaker: Cosmology now has a standard model. A relatively simple cosmological model describes the large-scale distribution of galaxies, detailed observations of the microwave background, observations of supernovae, and the abundances of light elements as well as a host of astronomical observations. In this model, the universe is spatially flat, homogeneous and isotropic on large scales. It is composed of ordinary matter, radiation, and dark matter and has a cosmological constant. The primordial fluctuations in this model are nearly scale-invariant Gaussian random fluctuations. I will highlight the key tests of the model and focus on the new results from the Wilkinson Microwave Anisotropy Probe. While this simple model has many successes, many key cosmological questions remain unanswered: what happened during the first moments of the big bang? What is the dark energy? What were the properties of the first stars? I will discuss the role of on-going and future CMB observations in addressing these key cosmological questions and describe how the combination of large-scale structure, supernova and CMB data can be used to address these questions. [Preview Abstract] |
Saturday, April 22, 2006 2:42PM - 3:18PM |
C5.00003: The Future of Theoretical Cosmology Invited Speaker: Over the course of the twentieth century, we went from knowing essentially nothing about the large-scale structure of the universe to knowing quite a bit: that it is expanding from a Big Bang, that it is approximately 14 billion years old, that there are perhaps 100 billion galaxies spread uniformly throughout the observable universe. Theory has progressed along with observation: general relativity now forms the basis for all our discussions about cosmology, and advances in quantum field theory and particle physics have allowed us to talk sensibly about nucleosynthesis, dark matter, and primordial inflation. In the twenty-first century, two obvious candidates stand out: the nature of the dark sector, and the beginning of time. With 95\% of the energy density of the universe apparently residing in dark matter and dark energy, the issues to be addressed by theorists span a wide range: What are these substances? Do they interact, with each other or with ordinary matter? Can they be detected in the lab? Why do they have the abundances we observe? Do they really exist, or are we being fooled by the behavior of gravity on large scales? Meanwhile, we will continue to stretch our theoretical models further into the past. Did the dark matter decouple from thermal equilibrium at early times? Do phase transitions in the early universe produce observable gravitational-wave backgrounds? Did inflation occur, and if so what were the dynamics of the inflaton field? Why did inflation start? Are there distinct domains within the universe, possibly with different properties? Can quantum gravity resolve the initial singularity, and connect us with a pre-Big-Bang phase? Why is the early universe different from the late universe -- what is the origin of time asymmetry? It's impossible to predict what the answers to any of these issues will turn out to be, but we can be confident that we won't be running out of interesting questions. [Preview Abstract] |
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