This is to remind you of our TODAY's Physics Colloquium:
Speaker: Prof. J. Ostriker, Cambridge / Princeton
Date: Wednesday, February 4, 2004
Time: 16:45 h (coffee at 16:15 h in front of auditorium)
Place: ETH Hönggerberg, HPV G4
Title: The Current State of Observational Cosmology
Abstract: A standard model for cosmology has emerged, sometimes called the concordance model, which is consistent with a broad suite of observations and not known to be inconsistent with any well controlled experiments. The universe begins as a hot big bang, goes through an inflationary phase (both of which are still under discussion), and then follows a path that is well verified by current data. Ordinary baryons represent a small fraction (~5%) of the critical density at the present time, dark matter of some unknown kind(s) is more abundant (~25% of the critical density) and a still more puzzling dark energy dominates the matter energy density (~70% of critical) with the total corresponding to the flat universe expectation: Wtot = 1. Potential fluctuations at about the level of 10-5 obey an initial distribution that is close to the n = 1 self-similar case, with amplitudes distributed in a Gaussian random fashion about the mean. Structure grows initially via gravitational instabilities with energy feedback from stars and accreting black holes ("feedback") playing a role that is relatively unimportant for the matter distribution but is dominant for the temperature distribution. Observations of the cosmic background radiation field and the distribution of galaxies are the two principal components in establishing this picture. While computer simulations of the quite definite mathematical model are very successful in reproducing the gross features of the universe (temporal history of galaxy formation, thermodynamic state of the intergalactic medium, lensing properties of the dark matter etc), we still have little or no understanding of the origin and nature of the dominant components of the universe.