2017/11/30 by Markus B. Fröb, William C. C. Lima
Physics and Astronomy · #Black Holes and Theoretical Physics #Cosmology and Gravitation Theories #Gauge theory #Inflation (cosmology) #Inflaton #Mathematical physics #Noncommutative and Quantum Gravity Theories #Observable #Physics #Propagator #Quantum #Quantum gravity #Quantum mechanics #Theoretical physics #gr-qc #hep-th
paper · pdf · doi:10.1088/1361-6382/aab427
published as Class. Quant. Grav. 35 (2018) 095010 · 37 pages, clarified discussion on gauge-invariant observables and added comments on the validity of the slow-roll expressions, matches published version
openalex publication_date 2018/03/05 · arxiv created 2018/03/27 · arxiv updated 2018/03/28 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
Abstract We make a proposal for gauge-invariant observables in perturbative quantum gravity in cosmological spacetimes, building on the recent work of Brunetti et al (2016 J. High Energy Phys . JHEP08(2016)032). These observables are relational, and are obtained by evaluating the field operator in a field-dependent coordinate system. We show that it is possible to define this coordinate system such that the non-localities inherent in any higher-order observable in quantum gravity are causal, i.e. the value of the gauge-invariant observable at a point x only depends on the metric and inflation perturbations in the past light cone of x . We then construct propagators for the metric and inflaton perturbations in a gauge adapted to that coordinate system, which simplifies the calculation of loop corrections, and give explicit expressions for relevant cases: matter- and radiation-dominated eras and slow-roll inflation.