In the first part of the talk, I will review constraints on Effective Field Theories that can be derived from first principles of UV completions. I will discuss results that go beyond the famous positivity bounds and I will briefly discuss applications for massive higher spin theories in flat space.
In the second part of the talk, I will discuss causality in gravitational systems beyond the classical limit. The focus will be the time delay in photon scattering against a massive spectator. I will show that the sign of the $\beta$-function, associated to the running of the electromagnetic gauge coupling, is related to the sign of the time delay for small impact parameter scatterings. The notion of “asymptotic causality”, according to which any particle must experience a positive time delay, is seen to be respected at loop level. Contrasted with asymptotic causality, I will discuss a local notion of causality, where the time delay of any particle is longer than the one of gravitons, which is seemingly violated by quantum effects.
INFN & DFA
