Dark Energy and Dark Matter in a Model of an Axion Coupled to a
  Non-Abelian Gauge Field
  We study cosmological field configurations (solutions) in a model in which
the pseudo-scalar phase of a complex field couples to the Pontryagin density of
a massive non-abelian gauge field, in analogy to how the Peccei-Quinn axion
field couples to the $SU(3)$-color gauge field of QCD. Assuming that the
self-interaction potential of the complex scalar field has the typical {\it
Mexican hat} form, we find that the radial fluctuations of this field can act
as {\it Dark Matter}, while its phase may give rise to tracking {\it Dark
Energy}. In our model, Dark-Energy domination will, however, not continue for
ever. A new component of dark matter, namely the one originating from the gauge
field, will dominate in the future.
