Dark energy properties from large future galaxy surveys
  We perform a detailed forecast on how well a {\sc 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 find that the combination of these three probes vastly
improves the survey's potential to measure the time evolution of dark energy.
In terms of a dark energy figure-of-merit defined as $(\sigma(w_{\mathrm p})
\sigma(w_a))^{-1}$, we find a value of 690 for {\sc Euclid}-like data combined
with {\sc Planck}-like measurements of the cosmic microwave background (CMB)
anisotropies in a 10-dimensional cosmological parameter space, assuming a
$\Lambda$CDM fiducial cosmology. For the more commonly used 7-parameter model,
we find a figure-of-merit of 1900 for the same data combination. 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 \emph{optimistic} scenario in
which $w_0$ deviates by as much as is currently observationally allowed from
$-1$, models with $\hat{c}_\mathrm{s}^2 = 10^{-6}$ and $\hat{c}_\mathrm{s}^2 =
1$ can be distinguished at more than $2\sigma$ significance. We emphasise that
constraints on the dark energy sound speed from cluster measurements are
strongly dependent on the modelling of the cluster mass function; significantly
weaker sensitivities ensue if we modify our model to include fewer features of
nonlinear dark energy clustering. Finally, we find that the sum of neutrino
masses can be measured with a $1 \sigma$ precision of 0.015~eV, (abridged)
