Seminar teorijske fizike

We suggest the gaussian von Neumann entropy as a measure of decoherence and classicality in quantum field theory (QFT). We then apply this idea to an interacting scalar field theory. We show how the
process of decoherence and classicisation can be observed in the context of a renormalised perturbative field theory. By making use of a quantum mechanical example, we compare our approach with the commonly used reduced density matrix approach to decoherence, and point out at the shortcomings of the latter approach.