Semiclassical Quantum Gravity  

In General > s.a. canonical and covariant quantum gravity [Minkowski and stability]; effective action; quantum geometrodynamics [WKB approximation].
* Idea: A sector of quantum gravity in which the probability distributions for values of all operators in a complete set of geometrical operators are sharply peaked around values corresponding to a classical geometry; This is usually taken to be necessary in order for the theory to make contact with reality.
@ General references: Barvinsky PLB(90) [and Wheeler-DeWitt equation, unitarity]; Lifschytz et al PRD(96)gq/94 [canonical]; Schuller & Wohlfarth PLB(05)gq/04 [and deformation of general relativity]; Livine BJP(05)gq-proc [deformations and information]; Kiefer et al PRD(05)gq [supersymmetric quantum gravity]; Hsu & Reeb CQG(08)-a0803 [unitarity and Hilbert space]; Bojowald et al PRD(11)-a1011 [quantum back-reaction by fluctuations]; Bradonjić a1104-GRF [the low-energy limit may not be general relativity]; Magueijo & Bethke a1207 [new "ground state" for quantum gravity and non-semiclassical nature of physical spacetime].
@ Lqg: Neville a0807 [spin networks]; Lin PhD-a0912 [and general relativity]; Smolin a1001 [and Newton's law of gravity]; Koslowski & Sahlmann Sigma(12)-a1109 [non-degenerate geometries]; Lin CQG(12)-a1111 [emergence of general relativity]; Bojowald & Paily PRD(12)-a1112 [effective actions and consequences]; Haggard et al PRD(13)-a1211 [twisted geometry, spin connection]; de Vegvar a1308/CQG [coherent states and length scales]; Han PRD(14) [covariant lqg and high-curvature UV corrections]; Alesci & Cianfrani PRD(14); Hamma et al a1506 [single-link wavefunctions and area law]; in Bianchi et al a1609 [loop expansion].
@ Lqg, asymptotically flat: Sengupta CQG(14)-a1309; Campiglia & Varadarajan CQG(14)-a1311, CQG(15)-a1412 + CQG+(15)aug.
@ Euclidean quantum gravity: Magnon JMP(81) [euclidean Levi-Civita as model for thermal fluctuations].
@ Spin foams: Magliaro et al CQG(08)-a0710 [with flipped vertex]; Bianchi & Satz NPB(08)-a0808 [and Regge calculus]; Conrady & Freidel PRD(08)-a0809 [Riemannian]; Miković & Vojinović a1010, a1103, CQG(11)-a1104 [background-field method, effective action]; Magliaro & Perini IJMPD(13)-a1105 [Regge gravity]; Dupuis & Livine JPCS(12)-a1111 [and simplicity constraints for topological BF theory]; Han CQG(14)-a1304 [large-spin regime], PRD(13)-a1304 [small Barbero-Immirzi parameter]; Han a1705 [emergence of general relativity]; > s.a. spin-foam models; Barrett-Crane Model.
@ In other approaches / theories: Giesel & Thiemann CQG(07)gq/06, CQG(07)gq/06 [algebraic quantum gravity]; Aastrup et al CMP(11)-a0907 [spectral triple over holonomy loops]; Kuzmichev & Kuzmichev a0910 [geometrodynamical, extremely small scales]; Aastrup & Grimstrup a0911 [lattice lqg]; Aastrup et al CQG(11)-a1012 [with matter, spectral triple approach]; Kiefer & Nikolić a1612-fs [Weyl gravity]; > s.a. semiclassical general relativity; classical limit of quantum theory.

Weave States in Loop Quantum Gravity > s.a. critical phenomena; renormalization.
* Idea: Weaves are kinematical states of quantum gravity which are simultaneous eigenstates of volume and area operators, and are meant to approximate classical geometries; Loops need to intersect for volumes not to vanish.
@ Flat space: Ashtekar et al PRL(92) [single loops]; Ashtekar in(93); Corichi & Reyes IJMPD(01)gq/00; Conrady CQG(05)gq/04; Shao et al IJTP(08) [Gaussian weave, metric operator].
@ Gravitons: Zegwaard NPB(92); Iwasaki & Rovelli IJMPD(93), CQG(94); Iwasaki gq/98.
@ Curved metrics: Borissov PRD(94) [plane waves]; Zegwaard PLB(93), CQG(93); Iwasaki gq/95 [Kerr-Newman]; > s.a. models in canonical quantum gravity.
@ Related topics: Grot & Rovelli GRG(97) [with intersecting loops]; Varadarajan & Zapata CQG(00)gq ["macroscopic'' operators]; Ma & Ling PRD(00)gq [degenerate metrics]; Ashtekar & Lewandowski CQG(01)gq [and Fock states]; Rovelli & Speziale CQG(06)gq [tetrahedron].

Semiclassical States / Continuum Limit > s.a. loop quantum gravity and topological field theories [Kodama state]; modified newtonian gravity.
* Continuum limit: From renormalization group arguments, for it to exist the theory should have critical behavior.
@ Continuum limit: Smolin LNP(95)gq [critical phenomena], gq/96; Kauffman & Smolin LNP(00)ht/98 [non-equilibrium critical phenomena]; Bojowald CQG(01)gq [loop quantum cosmology]; Ashtekar et al CQG(03)gq/02 [quantum mechanical model]; Dittrich a1409-in [of lqg].
@ Recovering classical spacetime: de Souza & Silveira gq/99 [general relativity]; Tsushima gq/02/PRD [Gaussian state, \(\langle\)metric\(\rangle\)]; Bojowald et al PRD(04)gq [coordinate time and length scales]; Freidel et al PRD(09)-a0905 [3D Boulatov model]; Kempf PRL(09)-a0908 [sampling spacetime with ultraviolet cutoff]; > s.a. geometrical operators.
@ Quantum corrections to general relativity: Cognola et al PRD(13)-a1304 [Gauss-Bonnet entropic corrections].
@ Coherent states: Thiemann CQG(01)ht/00, & Winkler CQG(01)ht/00, CQG(01)ht/00, CQG(01)ht/00; Sahlmann et al NPB(01)gq; Thiemann CQG(06)gq/02; Dasgupta JCAP(03)ht [around Schwarzschild]; Bojowald PRD(07)gq [dynamical, for quantum cosmology bounces]; Robles-Pérez et al a0709 [dark energy model]; Bahr & Thiemann CQG(09)-a0709 [gauge-invariant, U(1)], CQG(09)-a0709 [gauge-invariant, SU(2)]; Neville a0807, a0807 [planar]; Flori & Thiemann a0812 [flux coherent states]; Flori a0904 [re area-complexifier coherent states]; Bianchi et al PRD(10)-a0912; Freidel & Livine JMP(11)-a1005 [U(N) coherent states]; Oriti et al JPA(12)-a1110 [flux representation]; Oriti et al CQG(12)-a1202; Pittelli & Sindoni a1301 [and modified heat equations]; Ita & Soo AP(15)-a1408 [minimum-uncertainty, Gaussian solutions of the Wheeler-DeWitt equation and the Yamabe construction]; Schliemann PRA(15)-a1503 [properties of fluctuations]; Girelli & Sellaroli a1701 [SO*(2N) coherent states]; > s.a. minisuperspace [affine coherent states]; semiclassical quantum cosmology.
@ Statistical geometry: Bombelli gq/01-MG9 [random weave states]; Bombelli et al CQG(09)-a0905 [manifolds from graphs]; Díaz-Polo & Garay CQG(14)-a1308 [curvature from Voronoi graphs].
@ Condensate states: Koslowski a0709; Gielen CQG(14) [example, semiclassicality in terms of large-scale observables]; Oriti et al CQG(15)-a1501; Hamber a1708 [gravitational vacuum condensate].
@ Other proposals: Arnsdorf gq/99 [semiclassical connections]; Sharatchandra & Gadiyar gq/00 [fitting area and length bits]; Zimmermann gq/00-conf [entangled ensembles]; Miković CQG(04)gq, erratum CQG(06)gq [flat spacetime]; Cirilo-Lombardo & Prudêncio IJGMP(14)-a1309 [physics from supergeometries]; Chirco et al CQG(15)-a1408 [thermally correlated states].
@ With matter: Ita CQG(08)gq/07, CQG(08) [Klein-Gordon scalar, Kodama-like state]; Laddha & Varadarajan PRD(08)-a0805 [2D model]; Giesel et al a0911, Stottmeister & Thiemann a1504, a1504, a1504 [recovering quantum field theory on curved spacetimes, and Born-Oppenheimer decomposition]; > s.a. quantum field theory on curved backgrounds.

Phenomenology and Specific Spacetimes > s.a. quantum-gravity phenomenology; semiclassical quantum cosmology; gravitational thermodynamics.
@ Matter phenomenology: Smolin a0808 [effective deformed special relativity]; Major JPCS(12)-a1112 [angle and semiclassical states].
@ Black holes: Kiefer NPPS(97)gq [semiclassical states]; Frasca GRG(05)ht/04 [Schwarzschild, Bohr-Sommerfeld]; Dasgupta CQG(06)gq/05; Dasgupta & Thomas gq/06 [state degeneracy and entropy]; Cartin & Khanna PRD(06) [Schwarzschild interior]; Gambini & Pullin PRL(08)-a0805 [complete Schwarzschild spacetime]; Modesto IJTP(10)-a0811 [spacetime structure]; Husain & Terno PRD(10)-a0903 [gravity + scalar collapse]; Dasgupta Sigma(13)-a1203 [thermodynamics]; Nomura et al JHEP(15)-a1412 [limitations of semiclassical descriptions]; > s.a. quantum black holes.

main pageabbreviationsjournalscommentsother sitesacknowledgements
send feedback and suggestions to bombelli at – modified 15 aug 2017