A clock field interacting with matter in a Riemannian 4D space creates emergent Lorentzian patches, replacing the Big Bang singularity with a smooth signature-flip boundary and allowing an almost de Sitter early phase.
Rovelli,Loop quantum gravity,Living Rev
9 Pith papers cite this work. Polarity classification is still indexing.
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Pith papers citing it
abstract
The problem of finding the quantum theory of the gravitational field, and thus understanding what is quantum spacetime, is still open. One of the most active of the current approaches is loop quantum gravity. Loop quantum gravity is a mathematically well-defined, non-perturbative and background independent quantization of general relativity, with its conventional matter couplings. The research in loop quantum gravity forms today a vast area, ranging from mathematical foundations to physical applications. Among the most significative results obtained are: (i) The computation of the physical spectra of geometrical quantities such as area and volume; which yields quantitative predictions on Planck-scale physics. (ii) A derivation of the Bekenstein-Hawking black hole entropy formula. (iii) An intriguing physical picture of the microstructure of quantum physical space, characterized by a polymer-like Planck scale discreteness. This discreteness emerges naturally from the quantum theory and provides a mathematically well-defined realization of Wheeler's intuition of a spacetime ``foam''. Long standing open problems within the approach (lack of a scalar product, overcompleteness of the loop basis, implementation of reality conditions) have been fully solved. The weak part of the approach is the treatment of the dynamics: at present there exist several proposals, which are intensely debated. Here, I provide a general overview of ideas, techniques, results and open problems of this candidate theory of quantum gravity, and a guide to the relevant literature.
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Toller matrices T^(±) in causal spinfoam amplitudes satisfy T^(+) + T^(-) = D and admit equivalent definitions via analyticity, iε prescription, and boost-eigenvalue integrals that reproduce the Euclidean-to-Lorentzian Wick rotation.
Variational minimization of the squared Hamiltonian constraint in a truncated one-vertex loop gravity model yields three classes of near-kernel states; one factorized branch matches reduced Thiemann coherent states with high fidelity.
Loop quantum cosmology models harbor physical singularities or inconsistent space-time structures, with a new effective Friedmann equation revealing a sub-Planckian bounce after a singularity at infinite scale factor resembling a time-reversed big rip.
Thermodynamic consistency for quantum-improved Reissner-Nordström black holes permits arbitrary radial dependence in both Newton and electromagnetic couplings, while equation-action consistency requires an extra quantum energy-momentum tensor and specific properties for the Newton coupling.
A semiclassical deformed BTZ solution encodes Planck-scale kinematic modifications from curved momentum space in a nonlinear microscopic-to-ADM mass map, leaving local geometry and thermodynamics unchanged in form.
All minisuperspaces from symmetry reductions of the Einstein-Hilbert Lagrangian that obey the principle of symmetric criticality are canonically quantized and their Wheeler-DeWitt equations are solved.
Uniformly rotating particles decay via emission of negative-energy quanta due to the lack of a global vacuum for such observers, implying none can be regarded as stable.
Quantum corrections in rotating black holes produce detectable but spin-suppressed gravitational wave phase shifts in LISA EMRIs.
citing papers explorer
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The emergent Big Bang scenario
A clock field interacting with matter in a Riemannian 4D space creates emergent Lorentzian patches, replacing the Big Bang singularity with a smooth signature-flip boundary and allowing an almost de Sitter early phase.
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Toller matrices and the Feynman $i\varepsilon$ in spinfoams
Toller matrices T^(±) in causal spinfoam amplitudes satisfy T^(+) + T^(-) = D and admit equivalent definitions via analyticity, iε prescription, and boost-eigenvalue integrals that reproduce the Euclidean-to-Lorentzian Wick rotation.
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Emergent Thiemann coherent states in the near-kernel sector of quantum reduced loop gravity
Variational minimization of the squared Hamiltonian constraint in a truncated one-vertex loop gravity model yields three classes of near-kernel states; one factorized branch matches reduced Thiemann coherent states with high fidelity.
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Singularities in loop quantum cosmology
Loop quantum cosmology models harbor physical singularities or inconsistent space-time structures, with a new effective Friedmann equation revealing a sub-Planckian bounce after a singularity at infinite scale factor resembling a time-reversed big rip.
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Consistency in the Quantum-Improved Charged Black Holes
Thermodynamic consistency for quantum-improved Reissner-Nordström black holes permits arbitrary radial dependence in both Newton and electromagnetic couplings, while equation-action consistency requires an extra quantum energy-momentum tensor and specific properties for the Newton coupling.
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Quantum-Gravitational Backreaction in the BTZ Background from Curved Momentum Space
A semiclassical deformed BTZ solution encodes Planck-scale kinematic modifications from curved momentum space in a nonlinear microscopic-to-ADM mass map, leaving local geometry and thermodynamics unchanged in form.
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Canonical quantization of all minisuperspaces with consistent symmetry reductions
All minisuperspaces from symmetry reductions of the Einstein-Hilbert Lagrangian that obey the principle of symmetric criticality are canonically quantized and their Wheeler-DeWitt equations are solved.
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Decay of uniformly rotating particles
Uniformly rotating particles decay via emission of negative-energy quanta due to the lack of a global vacuum for such observers, implying none can be regarded as stable.
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Assessing EMRI Detectability of the Rotating Quantum Oppenheimer-Snyder Black Hole
Quantum corrections in rotating black holes produce detectable but spin-suppressed gravitational wave phase shifts in LISA EMRIs.