Matter and geometrical reference frames in quantum gravity models

Accessing the physical sector in quantum gravity models is a challenge, but also an important step towards analysing and testing such models.

One way to complete the quantisation program in the framework of loop quantum gravity is to choose physical reference frames from either the matter or geometric sector by means of which Dirac observables can be constructed in the framework of the relational formalism. The quantisation step then consists of finding representations for the corresponding algebra of Dirac observables that allow the dynamics to be quantised as well. In this way, an observer-dependent quantum field theory is obtained.

In this talk we will give a brief overview of the existing models and discuss their similarities and differences. Finally, we will present some examples of quantum gravity models with a particular choice of reference frame and discuss their physical properties.