Effect of dark energy sound speed and equation of state on CDM power
  spectrum
  We study the influence of equation of state $w$ and effective sound speed
$c_e$ of the dark energy perturbations on the cold dark matter(CDM) power
spectrum.We consider different cases of the equation of state and the effective
sound speed, the cold dark matter power spectrum is found to be generically
suppressed in these cases as compared to the $\Lambda$CDM model. The
suppression at different length scales depends on the value of $w$ and $c_e$,
and the effect of different $w$ is profoundly seen at all length scales. The
influence of sound speed is significantly seen only at the intermediate length
scales and is negligible at scales very much larger and smaller than the Hubble
scale.
