Early dark energy and its interaction with dark matter

We study a class of early dark energy models which has a substantial amount of dark energy in the early epoch of the Universe. We examine the impact of the early dark energy fluctuations on the growth of structure and the cosmic microwave background power spectrum in the linear approximation. Furthermore, we investigate the influence of the interaction between the early dark energy and the dark matter and its effect on the structure growth and cosmic microwave background. We finally constrain the early dark energy model parameters and the coupling between dark sectors by confronting different observations.