Dark energy properties from large future galaxy surveys

We perform a detailed forecast on how well a EUCLID-like survey will be able to constrain dark energy and neutrino parameters from a combination of its cosmic shear power spectrum, galaxy power spectrum, and cluster mass function measurements. We consider also the survey's potential to measure dark energy perturbations in models wherein the dark energy is parameterised as a fluid with a nonstandard non-adiabatic sound speed, and find that in an optimistic scenario in which w sub(0) deviates from -1 by as much as is currently observationally allowed, models with c super(2) sub(s) = 10 super(-6) and c super(2) sub(s) = 1 can be distinguished from one another at more than 2[sigma] significance. The 1[sigma] sensitivity to the effective number of relativistic species N super(ml) sub(eff) is approximately 0.03, meaning that the small deviation of 0.046 from 3 in the standard value of N super(ml) sub(eff) due to non-instantaneous decoupling and finite temperature effects can be probed with 1[sigma] precision for the first time.