Non-Commutative Geometry  

In General > s.a. [manifolds]; holonomy; quantum group; spectral geometry; Star Product.
* Idea: Non-commutative spaces are spaces with quantum group symmetry; They are based on (1) A non-commutative algebra defined by a star product which replaces the Abelian one of functions on a manifold, with a representation on a Hilbert space ; (2) An exterior differential algebra on (), with d taking n-forms into (n+1)-forms; (3) Possibly some additional structure, like a Dirac operator.
* History: A precursor was Snyder's spacetime with non-commuting coordinates; > s.a. quantum spacetime.

Non-Commutative Spacetime > s.a. linear connections; Hopf Algebra; matrix [models]; quantum spacetime; uncertainty.
* Semi-Riemannian: The spectral triple can be generalized; One replaces Hilbert spaces with Krein spaces, and Dirac operators are Krein-selfadjoint.
@ Intros: Majid LNP(00)ht, JMP(00)ht [and quantum groups]; Saito G&C(00); Masson mp/06-ln; Perini IJMPA(08)-in.
@ General references: Rosen AP(62) [complex combinations of x and p]; Chamseddine & Fröhlich ht/93-in; Heller & Sasin JMP(96) [singularities]; Madore & Mourad JMP(98)gq/96 [differential calculus and Minkowski space]; Mangano JMP(98)gq/97 [even D, path integral]; Strohmaier JGP(06)mp/01; Moretti RVMP(03)gq/02 [C*-algebra approach]; Romero et al PRD(03)ht [area quantization]; Chaichian et al PLB(04)ht, Kosinski & Maslanka ht/04 [interpretation]; Agostini ht/05 [operators and integration].
@ Locally non-commutative spacetime: Bahns & Waldmann RVMP(07)m.QA/06; Heller et al LMP(07) [C*-algebraic model].
@ And causality: Seiberg et al JHEP(00)ht; Chu et al IJMPA(06)ht/05.
@ Non-commutative coordinates: Doplicher et al CMP(95)ht/03; Toller qp/97, PRA(99)qp/98, IJTP(99)qp/98; Dzhunushaliev GRG(02)ht/01 [interpretation]; Jarvis & Morgan FPL(06) [Born reciprocity]; Bander ht/07 [Lorentz-invariant].
@ Non-commutative lattices: Bimonte et al PLB(94) [distances]; Balachandran et al JGP(96)ht/95 [from posets as finite topologies]; 't Hooft gq/96-in; Landi & Lizzi mp/98-in [projective systems]; > s.a. lattice field theories.
@ Fuzzy, quantum spacetime: Madore CQG(92); Balachandran et al NPPS(94)ht; Mack & Schomerus ht/94; Kehagias et al JMP(95)ht [modified Kaluza-Klein]; Sladkowski ht/96; Demaret et al gq/97; Francis phy/99; Requardt & Roy CQG(01) [fuzzy lumps]; Balachandran Pra(02)ht [rev]; de Albuquerque et al PRL(03)ht [Euclidean, from spectral action], MPLA(03)ht; > s.a. non-commutative field theory [quantum gravity], [quantum spacetime].
@ Particle propagation: Gamboa et al ht/01, Falomir et al PRD(02)ht [AB effect]; Amelino-Camelia et al PRD(03) [string-inspired]; Elias & Steele IJMPE(07)ht/06 [Snyder spacetime, massless scalar propagator].
@ Effective non-commutativity: Das & Gegenberg GRG-ht/04 [geodesics in Gödel-like spacetimes]; Corichi & Zapata a0705 [from 1D, polymeric quantum geometry]; > s.a. 3D quantum gravity.
@ Related topics: Masson qa/95 [submanifolds, quotients]; Coquereaux phy/96 [higher-order differentials]; Jaffe phy/97 [invariants]; Perrot LMP(99) [BRS cohomology & Chern character]; Hawkins CMP(04)m.QA/02 [obstructions], MPLA(03) [compatibility]; Schwarz NPB(03) [supergeometry]; Sardanashvily mp/03, mp/03, m.QA/07 [differential operators]; Licht ht/05-in [star product for Snyder's approach].
> Related topics: see higher-dimensional gravity; thermal radiation; types of distances; unimodular relativity.

Examples and Other Structures > s.a. principal fiber bundles; diffeomorphisms; minkowski space; schwarzschild; velocity.
* Example: The commutation relations between coordinates become [xm, xn] = i mn, where mn is a (constant) real antisymmetric matrix.
* Symmetries: Lie algebra symmetries are replaced by Hopf algebra symmetries.
@ Spheres: Madore CQG(97)gq; Pinzul & Stern PLB(01)ht [S2q, Dirac operator]; Sitarz LMP(01)mp, CMP(03)mp/01 [S4]; Freidel & Krasnov JMP(02) [star-product]; Connes & Dubois-Violette LMP(03), CMP(08)m.QA/05 [S3]; Lizzi et al JMP(05) [symmetries]; Dabrowski JGP(06) [S2q and S3q].
@ Other examples: Dimakis & Müller-Hoissen phy/97; Cerchiai et al EPJC(99)m.QA/98 [q-deformed line]; Connes & Dubois-Violette CMP(02)m.QA/01 [3D spherical manifolds]; Jackiw ht/01-in [physical]; Alexanian et al JGP(02) [CP2]; Fiore et al JMP(02) [real quantum plane]; van Suijlekom JMP(04)mp/03 [Lorentzian cylinder]; Lubo PRD(05)ht/04 [star product on fuzzy sphere from squeezed state]; Buric & Madore ht/04-in [2D, review], PLB(05) [2D, example]; > s.a. classical particles.
@ Tensor fields: Dvoeglazov S&S(02)mp, mp/03-in [derivatives]; Dimitrijevic et al JPA(04) [-deformed euclidean space].
@ Symmetries: Agostini et al IJMPA(04)ht/03 [Hopf algebra]; Calmet PRD(05); Chaichian et al PRL(05) [twisted Poincaré symmetry]; Gonera et al PRD(05)ht [global]; Gracia-Bondía et al PRD(06); Szabo CQG(06) [rev, and gravity]; Goswami a0704.
@ Related topics: Breslav & Zapatrin IJTP(00) [quantum/Greechie logic]; Díaz & Pariguán JPA(07)mp/06 [measures and path integration].

Phenomenology > s.a. non-commutative physics.
@ And DSR: Kowalski-Glikman & Nowak IJMPD(03); Heuson gq/03.
@ And Lorentz invariance: Anisimov et al PRD(02) [violations]; Chaichian et al PLB(04)ht.
@ Related topics: Tamaki et al PRD(02) [-Minkowski and astrophysics]; Vilela Mendes EPJC(05)ht/04; Hinchliffe et al IJMPA(04) [rev]; Martinis et al gq/05 [near-horizon geometry].

References > s.a. models of topology change.
@ Texts and reviews: Manin 91; Connes 94; Madore 95, gq/96 [connection and curvature], gq/99-in; Landi ht/97-in; Varilly phy/97-ln; Bigatti ht/98; Madore 99; Connes JMP(00)ht, m.QA/00; Martinetti ht/06-in; Kar 08.
@ General: Connes CRAS(80)ht/01; Dubois-Violette CRAS(88), et al JMP(90) [matrix algebras]; Coquereaux JGP(89), JGP(93); Connes LMP(95), JMP(95); Dubois-Violette qa/95 [derivations, connections], et al JMP(96) [curvature]; Kisil in(99)fa/97 [approaches]; Dimakis & Madore JMP(96) [differential calculi]; Jackiw & Pi PRL(02)ht/01 [coordinate changes]; Vacaru mp/02, mp/02 [Finsler, with local anisotropy]; Rennie & Varilly m.OA/06 [manifold reconstruction]; Chaichian et al ht/06 [Riemannian, framework]; Bertozzini et al a0801-in [categorical methods].
@ Almost commutative: Madore RPMP(99)gq/97 [Poisson structure and curvature]; Jureit & Stephan JMP(05), Jureit et al JMP(05) [classification].
@ Related topics: Dimakis & Müller-Hoissen JMP(99)gq/98 [discrete]; Lord mp/00-wd; Martinetti mp/01-PhD [distances]; Ponge LMP(08) ["lower-dimensional" volumes].


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