Developing non-perturbative methods might be crucial for understanding inflation and its predictions. In this talk, I will present a nonlinear study of the inflationary epoch of the Universe based on numerical lattice simulations. I will first focus on a model known as axion inflation, where the inflaton is coupled to a gauge field via Chern-Simons interaction. As a second example, I will consider a single-field model with a resonant feature in the potential. I will show that, in both cases, nonlinear effects have important consequences for the inflationary dynamics.

Both Einstein's equations and the field equations of a modified theory of gravity can be derived as equations of state from purely thermodynamical considerations, leading to the identification of GR with an equilibrium state of gravity and modified gravity with a non-equilibrium one. This breakthrough made the relationship between gravity and thermodynamics even more intriguing. I will present a new approach to the thermodynamics of modified gravity which is inspired by these results, but follows a starkly different path.

Boyer Théo
Cosmological magnetic fields 

Ivanez-Ballesteros Pilar

Supernova neutrinos and nonradiative neutrino decay

The expansion of the universe spontaneously breaks time translation by selecting a preferred reference frame. As a consequence, very much like a superfluid at zero temperature, the low-energy description of single field inflation can be organised in terms of the associated Goldstone mode of the broken symmetry (aka the phonon). Similar to particle colliders, if we were to scatter sound waves, the presence of additional heavy fields coupled to the medium would manifest as distinct peaks in the cross-section of the phonons.