ABSTRACT
The last decade has witnessed great advances in our understanding of the high redshift universe. The pace of observational cosmology and extragalactic astronomy has never been faster, and progress has been equally significant on the theoretical side. The key idea of currently popular cosmological scenarios, that primordial density fluctuations grow by gravitational instability driven by collisionless, cold dark matter (CDM), has been elaborated upon and explored in detail through large-scale numerical simulations on supercomputers, leading to a hierarchical (“bottom-up”) scenario of structure formation. In this model, the first objects to form are on subgalactic scales, and merge to make progressively bigger structures (“hierarchical clustering”). Ordinary matter in the universe follows the dynamics dictated by the dark matter until radiative, hydrodynamic, and star formation processes take over. Perhaps the most remarkable success of this theory has been the prediction of anisotropies in the temperature of the cosmic microwave background (CMB) radiation at about the level subsequently measured by the COBE satellite and most recently by the BOOMERANG, MAXIMA, DASI, CBI, Archeops, and WMAP experiments.
