Speaker: Noemi Frusciante (Instituto de Astrofísica e Ciências do Espaço, Universidade de Lisboa)
Given the wide sample of dark energy and modified gravity models (DE/MG) that address late time accelerated scenario and the high precision data, it becomes crucial to test DE/MG theories against data on large scales. In the quest of a model independent parametrization for gravity theories, the effective field theory formalism (EFT) has been applied to the phenomenon of cosmic acceleration. It is developed by using a perturbative approach in which an extra scalar degree of freedom appears only at the level of perturbations. I will present the implementation of this framework into CAMB/CosmoMC creating, what we dubbed, EFTCAMB/EFTCosmoMC. These patches allow to test gravity theories with the most recent data releases. To illustrate the use of these patches, I will show some results. Moreover, irrespectively of the MG model adopted, one has to ensure that the evolution of the modes associated to the extra DoF does not lead to pathological instabilities, such as ghost, gradient and tachyonic instabilities. I will present a thorough stability analysis of modified gravity theories in EFT language when the coupling to matter fields is also considered.