||Dark matter and dark energy are among the top unsolved mysteries
within today’s physics and astronomy. These unknown phenomena are
each supposed to explain a set of otherwise very puzzling observations.
However, instead of introducing two unknown new forms of matter, one
could equally try to unify their concepts into one. This is exactly what
Unified Dark Matter models try to do. For this approach to work such
models need to behave as dark matter on relatively small scales (to
account for structure formation), and as dark energy on relatively large
scales (to account for accelerated expansion). In this thesis the simplest
unified dark matter model is considered: the Chaplygin gas. In particular,
we investigate the possiblity for dark matter halo-like objects within this
model. We set up a general framework and try to solve the relevant
equations for both small radii and large radii close to the de-Sitter radius.
The solutions constructed indeed show large concentrations of energy
density are allowed, and in some cases the two regimes can be reasonably