Dwarf Galaxies as Cosmological Probes
  The Lambda Cold Dark Matter (LCDM) paradigm makes specific predictions for
the abundance, structure, substructure and clustering of dark matter halos, the
sites of galaxy formation. These predictions can be directly tested, in the
low-mass halo regime, by dark matter-dominated dwarf galaxies. A number of
potential challenges to LCDM have been identified when confronting the expected
properties of dwarfs with observation. I review our understanding of a few of
these issues, including the `missing satellites' and the `too-big-to-fail'
problems, and argue that neither poses an insurmountable challenge to LCDM.
Solving these problems requires that most dwarf galaxies inhabit halos of
similar mass, and that there is a relatively sharp minimum halo mass threshold
to form luminous galaxies. These predictions are eminently falsifiable. In
particular, LCDM predicts a large number of `dark' low-mass halos, some of
which should have retained enough primordial gas to be detectable in deep 21 cm
or H$_\alpha$ surveys. Detecting this predicted population of `mini-halos'
would be a major discovery and a resounding success for LCDM on small scales.
