Spacetime Geometry in Quantum Gravity  

Geometry in General > s.a. quantum gravity; quantum spacetime; semiclassical quantum gravity.
* Idea: Taking into account fluctuations around classical spacetimes is expected to lead to blurring of spacetime events and metric, fuzziness in causal relations and smearing of singularities; From a general quantum history or configuration extracting a classical one may not be possible because the ones with a classical interpretation are expected to be a very small subset.
@ General references: Motoyoshi NCB(93); Sonego PLA(95) [interpretation]; Amelino-Camelia Nat(99)gq/98, PLB(00)gq/99; Lehnert gq/07-MGXI [spacetime symmetries]; Hu JPCS(09)-a0903 [emergent spacetime]; Major CQG(10) [observational effects of atoms of space]; Hogan a1204 [covariant macroscopic quantum geometry]; Berenstein & Miller PRL(17)-a1605 [spacetime topology and geometry are not the result of an operator measurement].
@ Limitations in geometry extraction: Downes et al a1108 [quantum limit to estimation of the spacetime metric]; Bonder et al a1706; Nomura et al a1705 [in holography].
@ Deformed algebras, non-commutativity: Amelino-Camelia et al CQG(04)ht/03 [κ-Poincaré algebra]; Smolin NPB(06)ht/05 [energy-dependent metric, and DSR]; Amelino-Camelia et al PRD(13)-a1304 [physical characterization, from spacetime non-commutativity].
> Various approaches: see discrete models; higher-dimensional theories; non-commutative geometry; quantum cosmology; regge calculus.

Metric Fluctuations
* Rem: In the linearized theory they can be treated similarly to the electric and magnetic field fluctuations in Maxwell theory, but the gravitational probability distribution for fluctuations diverges when the temperature goes to zero.
@ General references: Ahluwalia Nat(99)gq; Ellis et al GRG(99)gq-GRF [general]; Hu et al IJTP(04) [semiclassical stability]; Kazakov G&C(04) [and the correspondence principle]; Requardt MPLA(07)gq/05 [and the holographic hypothesis]; Amelino-Camelia et al a1309 [scale invariance, and UV reduction to dimension 2]; Parkinson & Ford PRD(14)-a1311 [non-cancellation of quantum geometry fluctuations]; Nomura et al JHEP(15)-a1412 [spacetime-matter duality and frame dependence]; Białynicki-Birula CQG(15)-a1501 [zero-point fluctuations at finite temperature, using the Wigner function]; Wetterich PRD(17)-a1603 [correlation function for the metric]; Mathur a1705-GRF [spacetime thickness, spread of wave function in superspace].
@ Consequences, models: Acebal et al PLB(98), Miller GRG(00) [stochastic model]; Frenkel FP(02)qp/00 [Károlyházy]; Ford IJTP(05)gq-conf [test-particle Brownian motion]; Hu & Roura in(07)gq/06 [around a black hole]; Hogan PRD(08)-a0712 [holographic noise and interferometers]; Fröb et al JCAP(14)-a1403 [Riemann correlator in de Sitter spacetime]; Dzhunushaliev et al EPJC(15)-a1501 [modified gravity]; Ng a1701 [holographic principle, the cosmological constant, gravitational thermodynamics, and the dark sector].
@ Light-cone fluctuations: Neves et al PRL(10)-a1012 [and causality]; Ford et al AP(13) [non-linear optics analog]; > s.a. non-commutative field theory.
@ Experiments: Hogan a1208-proc [interferometry]; Wiens et al PRL(16) + news PhysOrg(17)jan [optical resonator].
@ Black holes, other: Aurilia & Spallucci a1309-GRF [uncertainty principle and Planck-scale black holes]; Casadio et al a1405-in [and minimum length]; Davila a1409 [limits on observation]; Giddings & Psaltis a1606 [time dependence of the shape and size of the black-hole shadow]; Barrau et al PLB(17)-a1606 [bouncing black holes and the Fermi gamma-ray excess]; Barceló et al CQG(17)-a1607 [fading to white holes]; > s.a. black-hole entropy and origin.

Related Topics > s.a. quantum-gravity effects on gravitation and cosmology.
@ General references: Bethke & Magueijo CQG(12)-a1108 [complex Immirzi parameter and chiral asymmetry]; Haggard PRD(13)-a1211 [pentahedral volume and chaos]; Cirilo-Lombardo & Prudêncio IJGMP(14)-a1309 [emergent metric]; Hogan PRD(17)-a1509 [exotic rotational correlations].
@ Gravitational collapse: Modesto IJTP(08)gq/06; Kowalski-Glikman & Starodubtsev gq/06 [and perturbation theory]; Kraus & Mathur IJMPD(15)-a1505-GRF [horizon avoidance]; Bonanno et al a1710 [and singularities]; > s.a. 3D quantum gravity.
> Black-hole related: see black-hole thermodynamics; black-hole types; quantum black holes [black-to-white-hole tunneling]; reissner-nordström solutions.
> Specific types of spacetimes: see differentiable manifolds; manifolds; singularities in quantum gravity; spacetime foam.
> Other related topics: see chaos in classical gravity; differential geometry [generalizations]; dimensionality of quantum spacetime [dimensional reduction]; lorentzian geometry [analogs]; quantum geometry.

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