Quantum Field Theory under external conditions: gravitation and electrodynamics

The semiclassical approximation in Quantum Field Theory is commonly used to study the propagation of quantized fields in classical backgrounds and accounts for fascinating non-perturbative quantum phenomena such as the spontaneous creation of particles induced by (non-trivial) external configurations. In this context, the computation of vacuum expectation values of physical observables becomes a complex issue, and advanced renormalization techniques are required to tame the new ultraviolet divergences caused by the external backgrounds. In curved spacetimes, all these interesting features are commonly studied within the Quantum Field Theory in Curved Spacetime framework, initiated in the ea…