Scalar field dark energy perturbations and the Integrated Sachs Wolfe   effect
  Dark energy perturbation affects the growth of matter perturbations even in scenarios with noninteracting dark energy. We investigate the Integrated Sachs Wolfe (ISW) effect in various canonical scalar field models with perturbed dark energy. We do this analysis for models belonging to the thawing and freezing classes. We show that between these classes there is no clear difference for the ISW effect. We show that on taking perturbations into account, the contribution due to different models is closer to each other and to the cosmological constant model as compared to the case of a smooth dark energy. Therefore considering dark energy to be homogeneous gives an overestimate in distinction between different models. However there are significant difference between contribution to the angular power spectrum due to different models. 
H. K. Jassal
astro-ph.CO