Gravitationally induced decoherence: from theoretical models to signatures in neutrino oscillations (PhD defense), Max Fahn (FAU and University of Bologna)

The formalism of Open Quantum Systems with linearised gravity as environment serves as a tool to predict the effective evolution of quantised matter systems under the influence of gravity. It is of use to analyse features of specific quantum gravity candidate theories and to search for signs of quantum gravity effects for instance in neutrino oscillations.
In the first part of the talk, a model consisting of a scalar matter field and linearised gravity as environment is considered. In order to deal with the gauge freedom present in the environment, the entire system is formulated in terms of relational observables that allow a physical interpreta- tion of temporal and spatial coordinates.
The resulting master equation, which is the effective time evolution equation for the quantised scalar field under the influence of gravity, exhibits UV-divergent terms. To extract the physics of a single scalar particle, the equation is projected onto the one-particle subspace and the individual terms are interpreted as Feynman diagrams. This yields the possibility to perform a QFT renor- malisation and the resulting master equation is cast into a completely positive Lindblad form using specific approximations.
In the last part, a quantum mechanical toy model for a neutrino propagating in an environment of gravitational waves is analysed. Its form is motivated by the above field theoretical model. The influence of gravity manifests here as a decoherence effect that damps the neutrino’s oscillations, allowing to get new insights on the physical properties of the model.