On Geometric Observables in Gravity

Abstract

Measures of geometry like distance and time are staples of classical gravity. While geometric quantities arise broadly in quantum gravity, their graviton corrections are less explored. In this paper, we study geometric observables in perturbative quantum gravity. We form distance and time observables that model measurements, including in the presence of spacetime fluctuations. Gravitational dressing ensures these constructions are coordinate invariant. Then we show how these finite-distance observables become memory and Shapiro time delay operators upon taking asymptotic limits. We compute leading graviton effects in correlators of geometric observables throughout. Altogether, our results identify a class of geometric observables that link experiments and operations on the celestial sphere.