In this talk, I will start by discussing some of the key obstacles one meets when without any prior assumption about the true model or any sort of parametrisation, tries to understand the nature of late-time acceleration of the universe from observations. I will then introduce and explain about those quantities which can instead be re-constructed in redshift and scale in a model- and parametrisation-free independent way, at the level of linear perturbations, and how these can be used to construct consistency tests for gravity models at large scales. In this context, I will particularly discuss about the reconstruction of scalar anisotropic stress, the latter being a key disciminator between genuine modifications of gravity and dark energy models. Finally, I will point out a fundamental relation between the existence of scalar anisotropic shear at large scales and the (non-trivial) propagation of tensor waves, as well as the observational implications for cosmology and astrophysics.
2014 November 13, 11:00
Faculdade de CiÍncias da Universidade de Lisboa (C6.2.51)
Campo Grande, 1749-016 Lisboa