UC Berkeley

Evidence has accumulated that descriptions of systems in quantum gravity depend strongly on various choices of gauge-fixing including a choice of "reference frame." We discuss several explicit examples of this reference frame dependence and, in doing so, clarify a number of general features of quantum gravity including the thermodynamics of spacetime, the holographic principle, and black hole complementarity.

Our discussion focuses on two superficially independent subjects. The first of these is that of holographic screens. These are codimension-one surfaces that are preferred from the perspective of the holographic principle. They are generated by a choice of null foliation and, in particular, can be fixed by the light cones of a worldline. We will study a class of holographic screens called past and future holographic screens and strengthen a recently proven area law for these surfaces. We then introduce a definition of holographic entanglement entropy associated with past and future holographic screens and, in doing so, provide new evidence for the importance of screens in quantum gravity. Our second major emphasis is on the black hole information paradox and the firewall paradox. We give a set of hypotheses for the microscopic structure of black holes that appears to be self-consistent and admit a smooth horizon despite the AMPS arguments. Our model relies on the principle that the quantum information associated with spacetime is both delocalized and reference frame dependent.