Interacting Hawking Radiation, Open QFTs and fluctuating hydrodynamics

In this talk, I will outline some of the recent developments in AdS/CFT which allow us to study open quantum field theories using holographic methods. More precisely, I will consider a quantum field theory (the system) coupled to a holographic field theory at finite temperature (the environment). A more intricate example is to derive the `fluctuating hydrodynamics' of the long-lived modes in a holographic field theory which dissipate into the microsocpic degrees of freedom. In both cases, the aim here to integrate out the holographic environment with an aim of obtaining an effective dynamics for the resulting open quantum field theory. This is done using semiclassical gravitational Schwinger-Keldysh saddle geometries obtained by  complexifying  black hole spacetimes. In addition to shedding light on open quantum systems coupled to strongly correlated thermal environments, these results also capture both the dissipative physics of black hole quasinormal modes, as well as that of the fluctuations encoded in outgoing Hawking quanta, and interactions between them.