Flavio Riccardi: "Quantum fields in de Sitter space and inflation: horizons, quasinormal modes, thermality, and renormalization"

Wednesday 11 Mar 2026, 12:30 → 14:00 Europe/Rome

The talk is intended as a pedagogical introduction to selected aspects of quantum field theory in curved spacetime, with emphasis on their interplay with gravitational physics in cosmological backgrounds.

In the first part, I will discuss the thermal and dissipative properties of quantum fields in de Sitter space, stressing the role of horizons and de Sitter isometries and clarifying the geometric origin of the associated thermal behavior. I will also describe how observables defined at the future and past horizons of a static observer provide a useful probe of the physics inside the causal patch, and how they lead to a natural notion of quasinormal modes in interacting quantum field theories.

In the second part, I will present a systematic framework for computing quantum corrections in time-dependent cosmological geometries, relevant for scalar perturbations and primordial gravitational waves. Particular emphasis will be placed on renormalization in curved spacetime, the structure of local covariant counterterms, and the comparison between different regularization prescriptions.