Testing gravity using the growth of large scale structure in the
  Universe
  Future galaxy surveys hope to distinguish between the dark energy and
modified gravity scenarios for the accelerating expansion of the Universe using
the distortion of clustering in redshift space. The aim is to model the form
and size of the distortion to infer the rate at which large scale structure
grows. We test this hypothesis and assess the performance of current
theoretical models for the redshift space distortion using large volume N-body
simulations of the gravitational instability process. We simulate competing
cosmological models which have identical expansion histories - one is a
quintessence dark energy model with a scalar field and the other is a modified
gravity model with a time varying gravitational constant - and demonstrate that
they do indeed produce different redshift space distortions. This is the first
time this approach has been verified using a technique that can follow the
growth of structure at the required level of accuracy. Our comparisons show
that theoretical models for the redshift space distortion based on linear
perturbation theory give a surprisingly poor description of the simulation
results. Furthermore, the application of such models can give rise to
catastrophic systematic errors leading to incorrect interpretation of the
observations. We show that an improved model is able to extract the correct
growth rate. Further enhancements to theoretical models of redshift space
distortions, calibrated against simulations, are needed to fully exploit the
forthcoming high precision clustering measurements.
