2011/12/08 by Martin Bojowald, George M. Paily · 4 citations
Physics and Astronomy · #Black Holes and Theoretical Physics #Canonical quantum gravity #Classical mechanics #Cosmology and Gravitation Theories #Euclidean quantum gravity #General covariance #General relativity #Gravitation #Hořava–Lifshitz gravity #Immirzi parameter #Loop quantum cosmology #Loop quantum gravity #Noncommutative and Quantum Gravity Theories #Physics #Problem of time #Quantum #Quantum dynamics #Quantum geometry #Quantum gravity #Quantum mechanics #Quantum process #Semiclassical gravity #Spin foam #Theoretical physics #astro-ph.CO #gr-qc #hep-th
paper · pdf · doi:10.1103/physrevd.86.104018
published as Phys. Rev. D 86 (2012) 104018 · 44 pages
arxiv created 2011/12/08 · openalex publication_date 2012/11/06 · arxiv updated 2013/05/29 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
Canonical methods can be used to construct effective actions from deformed covariance algebras, as implied by quantum-geometry corrections of loop quantum gravity. To this end, classical constructions are extended systematically to effective constraints of canonical quantum gravity and applied to model systems as well as general metrics, with the following conclusions: (i) Dispersion relations of matter and gravitational waves are deformed in related ways, ensuring a consistent realization of causality. (ii) Inverse-triad corrections modify the classical action in a way clearly distinguishable from curvature effects. In particular, these corrections can be significantly larger than often expected for standard quantum-gravity phenomena. (iii) Finally, holonomy corrections in high-curvature regimes do not signal the evolution from collapse to expansion in a ``bounce,'' but rather the emergence of the Universe from Euclidean space at high density. This new version of signature-change cosmology suggests a natural way of posing initial conditions, and a solution to the entropy problem.