  In recent years, simple models of galaxy formation have been shown to provide
reasonably good matches to available data on high-redshift luminosity
functions. However, these prescriptions are primarily phenomenological, with
only crude connections to the physics of galaxy evolution. Here we introduce a
set of galaxy models that are based on a simple physical framework but
incorporate more sophisticated models of feedback, star formation, and other
processes. We apply these models to the high-redshift regime, showing that most
of the generic predictions of the simplest models remain valid. In particular,
the stellar mass--halo mass relation depends almost entirely on the physics of
feedback (and is thus independent of the details of small-scale star formation)
and the specific star formation rate is a simple multiple of the cosmological
accretion rate. We also show that, in contrast, the galaxy's gas mass is
sensitive to the physics of star formation, although the inclusion of
feedback-driven star formation laws significantly changes the naive
expectations. While these models are far from detailed enough to describe every
aspect of galaxy formation, they inform our understanding of galaxy formation
by illustrating several generic aspects of that process, and they provide a
physically-grounded basis for extrapolating predictions to faint galaxies and
high redshifts currently out of reach of observations. If observations show
violations from these simple trends, they would indicate new physics occurring
inside the earliest generations of galaxies.
