Density perturbation in an interacting holographic dark energy model
  The present work deals with the evolution of the density contrasts for a
cosmological model where along with the standard cold dark matter (CDM), the
present Universe also contains holographic dark energy (HDE). The
characteristic infra-red (IR) cut-off is taken as the future event horizon. The
HDE is allowed to interact with the CDM. The equations for the density
contrasts are integrated numerically. It is found that irrespective of the
presence of an interaction, the matter perturbation has growing modes. The HDE
is also found to have growth of perturbation, so very much like the CDM, thus
can also cluster. The interesting point to note is that the density contrast
corresponding to HDE has a peak at recent past and is decaying at the present
epoch. Another feature is that IR cut-off as the event horizon does not
naturally produce accelerated expansion of the Universe in the presence of an
interaction.
