Title: Cosmological implications of a non-minimally coupled scalar field: Dark Energy and perturbations from Inflation.
Abstract: I discuss the cosmological imprints of a non-minimally coupled scalar field that drives the late-time acceleration of the Universe and the time variation of the effective Newton constant. In a full covariant description, I describe the background and perturbed evolution of the Universe for different choices of the scalar field coupling. I describe the linear perturbations and their impact on the cosmological observables, particularly focusing on a new set of isocurvature initial conditions. I then show the current cosmological constraints and forecasts on the model and Post-Newtonian parameters. In a second part of the talk, I address the question of the equivalence of inflationary predictions in the Einstein and Jordan frame and discuss the ambiguity of the definition of isocurvature perturbations in the Jordan frame.