Uniqueness of the Fock quantization of scalar fields in spatially flat cosmological spacetimes

Understand

We study the Fock quantization of scalar fields in (generically) time dependent scenarios, focusing on the case in which the field propagation occurs in --either a background or effective-- spacetime with spatial sections of flat compact topology.

• The discussion finds important applications in cosmology, like e.g.
• in the description of test Klein-Gordon fields and scalar perturbations in Friedmann-Robertson-Walker spacetime in the observationally favored flat case.
• Two types of ambiguities in the quantization are analyzed.