Speaker
Description
Several major open problems in cosmology involve spacetime-filling media with unknown microphysics, and can only be probed through their gravitational effects. This observation motivates a systematic open-system approach, in which gravity evolves in the presence of a generic, unobservable environment.
After a brief review of the Schwinger–Keldysh path integral formalism for open systems, I will present a general framework for open gravitational dynamics, with particular attention to the constraints imposed by diffeomorphism invariance. As an application, I will focus on inflation, where the framework reproduces the known Open Effective Field Theory of Inflation in the decoupling limit and naturally extends it to include gravitational interactions. These yield both conservative and dissipative corrections to graviton propagation. Remarkably, leading-order gravitational birefringence is dissipative, while conservative birefringence only appears at higher derivative order — contrary to the electromagnetic case.
