Space-time physics in background-independent theories of quantum gravity

Abstract

Background independence is often emphasized as an important property of a quantum theory of gravity that takes seriously the geometrical nature of general relativity. In a background-independent formulation, quantum gravity should determine not only the dynamics of space-time but also its geometry, which may have equally important implications for claims of potential physical observations. One of the leading candidates for background-independent quantum gravity is loop quantum gravity. By combining and interpreting several recent results, it is shown here how the canonical nature of this theory makes it possible to perform a complete space-time analysis in various models that have been proposed in this setting. In spite of the background-independent starting point, all these models turn out to be non-geometrical and even inconsistent to varying degrees, unless strong modifications of Riemannian geometry are taken into account. This outcome leads to several implications for potential observations as well as lessons for other background-independent approaches.

arXiv comment28 pages, 4 figures

References in corpus (31)

• Dilaton Gravity in Two Dimensions
• Lorentz invariance and quantum gravity: an additional fine-tuning problem?
• Quantum Transfiguration of Kruskal Black Holes
• A Quantum Gravity Extension of the Inflationary Scenario
• Loop quantization of the Schwarzschild black hole
• An Extension of the Quantum Theory of Cosmological Perturbations to the Planck Era
• Quantum cosmology: a review
• Hybrid Quantum Gowdy Cosmology: Combining Loop and Fock Quantizations
• Effective line elements and black-hole models in canonical (loop) quantum gravity
• Hamiltonian formulation of f(Riemann) theories of gravity
• Covariance in models of loop quantum gravity: Spherical symmetry
• Polymer Schwarzschild black hole: An effective metric
• Towards an Anomaly-Free Quantum Dynamics for a Weak Coupling Limit of Euclidean Gravity
• Towards reconstructing the quantum effective action of gravity
• Non-singular black holes and the Limiting Curvature Mechanism: A Hamiltonian perspective
• A no-go result for covariance in models of loop quantum gravity
• Constraint algebra in LQG reloaded : Toy model of a U(1)^{3} Gauge Theory I
• Covariance in models of loop quantum gravity: Gowdy systems
• Asymptotic non-flatness of an effective black hole model based on loop quantum gravity
• Critical collapse of a scalar field in semiclassical loop quantum gravity
• New 2D dilaton gravity for nonsingular black holes
• Inhomogeneities, loop quantum gravity corrections, constraint algebra and general covariance
• Constraint algebra in LQG reloaded : Toy model of an Abelian gauge theory - II Spatial Diffeomorphisms
• Comment on [arXiv:1106.1417] "Small Lorentz violations in quantum gravity: do they lead to unacceptably large effects?"
• Non-covariance of the dressed-metric approach in loop quantum cosmology
• Towards an Anomaly-Free Quantum Dynamics for a Weak Coupling Limit of Euclidean Gravity: Diffeomorphism Covariance
• Unsettling physics in the quantum-corrected Schwarzschild black hole
• The constraint algebra in Smolins' $G\to 0$ limit of 4d Euclidean Gravity
• Generalized 2D dilaton gravity and KGB
• Non-covariance of "covariant polymerization" in models of loop quantum gravity
• A covariant polymerized scalar field in loop quantum gravity

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