We will study the impact of these nonstandard scenarios on observations such as the galaxy clustering, weak lensing cosmic shear, and Cosmic Microwave Background anisotropies. We also wish to make detailed forecasts for future missions such as Euclid, to study how/whether these observations can discriminate between these models.
(2) We will investigate the existence and properties of nonlinear screening mechanisms (e.g., those that rely on nonstandard derivative terms) and test them against current const raints on smaller subgalactic scales.
It is equally important to also investigate the small-scale astrophysical signatures of these models. Indeed, it has been shown for several models [e.g., f(R)-theories] that Solar System constraints are so tight that they can be stronger than cosmological observations (as screening mechanisms do not always ensure a convergence to General Relativity that is fast enough on small scales), although they apply to very different regimes. Therefore, when we study a modified- gravity model beyond linear order, it is critical to investigate both the small-scale astrophysical regime and the large-scale cosmological regime before we can conclude the model is a realistic proposal. This regime has not been studied as much as the la rge-scale cosmological limit, hence this remains a promising complementary tool to discriminate theoretical models. For instance, we will study stellar instabilities or oscillation modes, and strong lensing effects.
This task will be performed in the firs t six months of the project by two PhD students and coordinated by two senior members (one from each node in both cases).
(3) Massive gravity:
A gravitational modification that has recently a