Perturbations for transient acceleration
  According to the standard $\Lambda$CDM model, the accelerated expansion of
the Universe will go on forever. Motivated by recent observational results, we
explore the possibility of a finite phase of acceleration which asymptotically
approaches another period of decelerated expansion. Extending an earlier study
on a corresponding homogeneous and isotropic dynamics, in which interactions
between dark matter and dark energy are crucial, the present paper also
investigates the dynamics of the matter perturbations both on the Newtonian and
GR levels and quantifies the potential relevance of perturbations of the
dark-energy component. In the background, the model is tested against the
Supernova type Ia (SNIa) data of the Constitution set and on the perturbative
level against growth rate data and the data of the 2dFGRS project. Our results
indicate, that a transient phase of accelerated expansion is not excluded by
current observations.
