Observables for Quantum Gravity: Going Nonperturbative

Abstract: The physical nature and explicit construction of observables in quantum gravity depend on length scale and context, and tend to be very different in perturbative and nonperturbative regimes. My talk will focus on the latter, which is characterised by the absence of a pre-existing background and where spacetime is not described by a smooth metric tensor. What constitutes appropriate (pre-)gravitational observables near the Planck scale is not known a priori, and their operational definition depends on how diffeomorphism symmetry is implemented nonperturbatively. Natural candidates are "quantum generalisations" of nonlocal classical observables, which in general will need to be renormalized and may display unexpected, anomalous behaviour. To compare with classical results, one also needs some control on how to coarse-grain. The construction and implementation of nonperturbative quantum observables poses creative and technical challenges that can be addressed successfully in sufficiently complete candidate theories, as I will illustrate in the context of Causal Dynamical Triangulations.

general relativity and quantum cosmologyHEP - theoryquantum physics

Audience: researchers in the topic

Quantum Gravity Across Approaches

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