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GR: Fachverband Gravitation und Relativitätstheorie

GR 12: Quantum gravity (joint session MP/GR)

GR 12.3: Talk

Thursday, March 24, 2022, 12:00–12:20, MP-H5

A master equation for gravitationally induced decoherence of a scalar field — •Max Joseph Fahn, Kristina Giesel, and Michael Kobler — Institute for Quantum Gravity, Department of Physics, FAU Erlangen-Nürnberg, Staudtstr. 7, 91058 Erlangen, Germany

In the talk, we present the derivation of a decoherence model containing a scalar field coupled to a gravitational environment. With such a model, one can predict quantum gravity effects in the scalar field's dynamics that arise due to the presence of gravity. Starting with full general relativity in Hamiltonian form expressed in Ashtekar's connection formulation, we focus on weak gravitational interactions in an asymptotically flat universe, modelled by gravitational waves propagating on a fixed background, and the scalar field as matter component. Firstly, we construct appropriate observables (gauge invariant quantities) for the model which become elementary variables in the reduced phase space of the model. Afterwards a reduced phase space quantisation using Fock quantisation is performed. With the help of the projection operator technique, we derive a second order time-convolutionless master equation, that is an effective evolution equation which predicts the temporal evolution of the scalar field, including the gravitational interaction effectively in terms of certain operators, whose form is a result of the model under consideration and several physical assumptions. These additional terms lead to physical effects like dissipation or decoherence of the matter field induced by gravity. Finally, we briefly discuss possible applications of the model's master equation.