The next cosmology seminar takes place on Friday 22th of May, room E349 at 2:00pm. We will have the pleasure to listen to Samuel Sánchez López from the Institut d’Astrophysique de Paris (IAP, France).
At 2:00pm, room E349, Samuel Sánchez López will be talking about
Palatini Gravity Across Cosmic History
The ΛCDM model provides an excellent fit to a broad range of cosmological data spanning different epochs and scales. However, recent tensions between datasets, together with the unknown nature of inflation and dark energy, motivate the consideration of gravity beyond the Einstein-Hilbert action. In this talk, I will discuss several aspects of cosmology and weak-field gravity in the Palatini formulation, where the metric and connection are treated as independent fields.
I will first present Palatini \(R^2\) gravity as a framework for inflationary model building, emphasizing how higher-curvature terms modify the inflationary dynamics and the resulting predictions. I will then discuss scalar-induced gravitational waves generated during radiation domination, showing how Palatini \(f(R)\) gravity can leave distinctive signatures in the stochastic gravitational-wave spectrum. Turning to late times, I will present non-minimally coupled quintessence in light of recent DESI data, focusing on the existence of a de Sitter attractor and the observational preference for dynamical dark energy. Finally, I will discuss Solar-System constraints on scalar-tensor gravity through a unified post-Newtonian treatment, deriving the effective scalar mass, gravitational coupling, and the PPN parameters γ and β. Together, these results show how observations across cosmic history can probe not only deviations from General Relativity, but also the variational formulation of gravity itself.