One of the biggest challenges in present day cosmology is to explain the "missing mass" which forms over 95% of the content of the universe. This emerged as important in the 1970's when astronomers compared systematically the gravitational masses of galaxies and galaxy groups with their total content of stars gas and dust, finding that over nine tenths of the gravitational mass could not be accounted for. It was also realised that the discs of spiral galaxies would be unstable without the presence of a massive dark halo. Then the inflationary model which explains the observed isotropy of the cosmic microwave background (CMB) radiation, implies a "flat" universe while the light element abundances predicted in the standard model Big Bang cosmology show measured values implying that "normal" baryonic matter can make up less than 5% of the mass needed for the universe to be flat.
Our best models accounting for the observed large-scale distribution of mass and velocity of galaxies and clusters start with density fluctuations in an inflationary universe, and require a dominant mass component of non-baryonic matter non-relativistic at the time of its decoupling from the background radiation. The best of these "cold dark matter" (CDM) models, however, reque a CDM density only -30% of that required to close the universe, in apparent contradiction with inflationary predictions. This discrepancy was dramatically addressed by the discovery, using supernovae as standard distance candles that the universe is apparently accelerating. The vacuum energy which can produce this acceleration can also account for the -65% of the gravitational field not produced by baryonic matter or CDM, while the flatness of the universe was recently confirmed by measurements of the power spectrum of CMB fluctuations.
Thus we have an apparently coherent picture, but with two big questions: what is the nature of the CDM, and what is the nature of the dark energy?
This Winter School (Summer School) will address these issues from both theoretical and observational points of view. Lecture series on inflationary cosmology, missing mass in galaxies, baryonic dark matter, structure formation in CDM models, laboratory searches for CDM particles ("WIMPS"), the use of gravitational lensing to explore structure on local and global scales, recent CMB fluctuation measurements, and evidence for an accelerating universe will make up the content of the school, which should be suitable for young researchers in cosmology, astrophysics, and particle physics.