Modeling the High-z Universe: Probing Galaxy Formation
  We discuss how the conditions at high redshift differ from those at low
redshift, and what the impact is on the galaxy population. We focus in
particular on the role of gaseous dissipation and its impact on sustaining high
star formation rates as well as on driving star-bursts in mergers. Gas
accretion onto galaxies at high redshifts occurs on a halo dynamical time
allowing for very efficiently sustained star formation. In addition cold
accretion flows are able to drive turbulence in high redshift disks at the
level observed if at least 20% of the accretion energy is converted into random
motion in the gaseous disk. In general we find that the fraction of gas
involved in galaxy mergers is a strong function of time and increases with
redshift. A model combining the role of dissipation during mergers and
continued infall of satellite galaxies allows to reproduce the observed
size-evolution of early-type galaxies with redshift. Furthermore we investigate
how the evolution of the faint-end of the luminosity function can be explained
in terms of the evolution of the underlying dark matter evolution.
