July 18, 2024
The diffeomorphism symmetry of general relativity leads to the infamous problem of time, haunting especially canonical approaches to quantum gravity. The core question it raises is how to define quantum dynamics in a diffeomorphism-invariant context (in the absence of external references such as boundaries) and is intimately tied with the more general question of what are observables in a background-independent quantum theory. Relational observables are one way of addressing these challenges. The underlying idea is to localize physical quantities of interest relative to other dynamical degrees of freedom, chosen as a dynamical reference system, rather than a spacetime background. A comprehensive relational picture then warrants covariance to be extended to changes of dynamical reference system. In this talk, I will offer an overview over achievements and challenges of the relational approach, as well as perspectives on quantum gravity arising therefrom. Recorded on 07/10/2020