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Quantum Gravity: Motivations and Alternatives [PDF]
, 2009 The mutual conceptual incompatibility between General Relativity and Quantum Mechanics / Quantum Field Theory is generally seen as the most essential motivation for the development of a theory of Quantum Gravity.
Hedrich, Reiner
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Midisuperspace Models of Canonical Quantum Gravity [PDF]
International Journal of Theoretical Physics, 1999 29 pages, RevTex, contribution to "Quantum Gravity in the Southern Cone II", Bariloche, Argentina, January 6-10 ...
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Spacetime and the Philosophical Challenge of Quantum Gravity [PDF]
, 2001 We survey some philosophical aspects of the search for a quantum theory of gravity, emphasising how quantum gravity throws into doubt the treatment of spacetime common to the two `ingredient theories' (quantum theory and general relativity), as a 4 ...
Butterfield, Jeremy +3 more
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Spin foam models for quantum gravity [PDF]
Classical and Quantum Gravity, 2003 In this article we review the present status of the spin foam formulation of non-perturbative (background independent) quantum gravity. The article is divided in two parts. In the first part we present a general introduction to the main ideas emphasizing their motivations from various perspectives.
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Solving puzzles in deformed JT gravity: phase transitions and non-perturbative effects
Journal of High Energy Physics, 2021 Recent work has shown that certain deformations of the scalar potential in Jackiw-Teitelboim gravity can be written as double-scaled matrix models. However, some of the deformations exhibit an apparent breakdown of unitarity in the form of a negative ...
Clifford V. Johnson, Felipe Rosso
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SPIN FOAM MODELS OF QUANTUM GRAVITY [PDF]
Mathematical, Theoretical and Phenomenological Challenges Beyond the Standard Model, 2005 We give a short review of the spin foam models of quantum gravity, with an emphasis on the Barret-Crane model. After explaining the shortcomings of the Barret-Crane model, we briefly discuss two new approaches, one based on the 3d spin foam state sum invariants for the embedded spin networks, and the other based on representing the string scattering ...
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Diffeomorphism Symmetry in Quantum Gravity Models [PDF]
Advanced Science Letters, 2009 We review and discuss the role of diffeomorphism symmetry in quantum gravity models. Such models often involve a discretization of the space-time manifold as a regularization method. Generically this leads to a breaking of the symmetries to approximate ones, however there are incidences in which the symmetries are exactly preserved.
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An effective matrix model for dynamical end of the world branes in Jackiw-Teitelboim gravity
Journal of High Energy Physics, 2022 We study Jackiw-Teitelboim gravity with dynamical end of the world branes in asymptotically nearly AdS2 spacetimes. We quantize this theory in Lorentz signature, and compute the Euclidean path integral summing over topologies including dynamical branes ...
Ping Gao +2 more
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Interpreting Quantum Gravity. [PDF]
, 2005 This is an essay review of two textbooks on quantum gravity by Carlo Rovelli and Claus ...
Dean Rickles, Rickles, Dean
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Renormalizable and Unitary Model of Quantum Gravity [PDF]
Symmetry, 2019 We consider R + R 2 relativistic quantum gravity with the action where all possible terms quadratic in the curvature tensor are added to the Einstein-Hilbert term. This model was shown to be renormalizable in the work by K.S. Stelle. In this paper, we demonstrate that the R + R 2 model is also unitary contrary to the statements made
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