Quantum Reference Frames at the Boundary of Spacetime

Understand

An analysis is given of the local phase space of gravity coupled to matter to second order in perturbation theory.

• Working in local regions with boundaries at finite distance, we identify matter, Coulomb, and additional boundary modes.
• The boundary modes take the role of reference frames for both diffeomorphisms and internal Lorentz rotations.
• Passing to the quantum level, we identify the constraints that link the bulk and boundary modes.