Initial-Value Formulation of General Relativity  

Based on a Spacelike Hypersurface > s.a. canonical formulation and connection variables; constraints; Sandwich Conjecture.
* Idea: We assign the value of the 3-metric qab and the extrinsic curvature Kab on an initial 3D spacelike hypersurface , subject to some constraints, and then evolve them and find the full 4-metric in spacetime; If matter is present, we assign also the local mass density and current density j, assumed to satisfy the energy condition 2 j aja.
* Variables: The usual dynamical variables are qab and Kab, and the choice of gauge is represented by the lapse N and shift Na (and an initial choice of gauge/coordinates at t = 0); > s.a. gauge transformations.
* Alternatively: One can give, on , the distribution and flow of mass-energy, , j a and Sab, up to a conformal factor, and the conformal 3-geometry and its rate of change.
* Evolution equations: For vanishing shift Na = 0, the metric and extrinsic curvature (satisfying the constraints) evolve according to

qab· = 2 N Kab ,   Kab· = –DaDb N – 2 N Kam KbmN KKab3Rab N + 8G N qam qbm(T mnTgmn) .

* Hyperbolic, curvature-based: A formulation for arbitrary lapse and shift based on a wave equation for curvature.

References > s.a. constraints for general relativity; numerical relativity; Peeling Properties.
@ General: Bonnor JMM(60) [re uniqueness]; Choquet-Bruhat & Geroch CMP(69); York PRL(71); Fischer & Marsden JMP(72); York JMP(72), PRL(72), JMP(73), in(79); O'Murchadha & York JMP(73), PRD(74), PRD(74); Smarr & York PRD(78); Fischer & Marsden in(79); Choquet-Bruhat & York in(80); York in(82); Isenberg FP(86); Choquet-Bruhat & York gq/95, gq/96; York gq/98; Friedrich & Rendall LNP(00)gq-in; York gq/04-in [qab + Kab]; Chrusciel & Friedrich ed-04; Brown PRD(05) [conformal-traceless].
@ Intros, reviews: Gourgoulhon gq/07-ln.
@ Hyperbolic: Estabrook et al CQG(97)gq [first-order]; Yoneda & Shinkai PRL(99)gq/98, IJMPD(00)gq/99 [Ashtekar variables]; Alvi CQG(02) [dynamical N and Na]; Tarfulea gq/05-PhD [constraint-preserving boundary conditions].
@ Hyperbolic, curvature-based: Abrahams et al PRL(95)gq, CQG(97)gq/96; Abrahams & York gq/96; Anderson et al gq/97, gq/99-in; Choquet-Bruhat et al gq/98-in; Lau IJMPD(98)gq/96 [based on forms]; Anderson & York PRL(99)gq.
@ Other gauges: Andersson & Moncrief AHP(03)gq/01 [elliptic-hyperbolic]; Paschalidis et al PRD(07)gq/05 [well-posedness].
@ Related topics: Durrer & Straumann HPA(88) [applications]; Husain PRD(99)gq/98 [matter fields]; Frittelli & Reula JMP(99)gq [conformally decoupled]; Rácz CQG(01)gq [and symmetries]; Khokhlov & Novikov CQG(02)gq/01 [gauge stability]; Alcubierre et al a0907 [with Maxwell fields, and multi-black-holes].

Existence and Uniqueness of Solutions
* Situation: The initial-value problem is known to be well-defined for globally hyperbolic spacetimes, time-non-orientable spacetimes whose orientable double cover is globally hyperbolic, and some cases of spacetimes with closed timelike curves.
* Different 3-topologies: They all admit good (vacuum) data, but generically evolve into spacetimes that are locally de Sitter and develop singularities.
@ Reviews: Rendall LRR(98), LRR(00)gq, LRR(02)gq + LRR(05)gq.
@ Long-time evolution: Friedrich CMP(86); Christodoulou CQG(99)A [and singularities]; Anderson CMP(01) [and 3-geometry]; Klainerman & Nicolò 02; Lindblad & Rodnianski CMP(05)m.AP/03 [global existence], m.AP/04 [global stability of Minkowski]; Choquet-Bruhat & Friedrich CQG(06)gq [Einstein-dust and Einstein-Maxwell-dust, compact support].
@ Closed 3-manifolds: Andersson gq/99-in; Scannell m.DG/00 [flat spacetime].
@ Different 3-topologies: Witt PRL(86); Morrow-Jones; Bengtsson & Holst CQG(99)gq [locally de Sitter]; Isenberg et al AHP(03)gq/02 [all D's]; Choquet-Bruhat et al CQG(06)gq [Einstein-Maxwell, higher dimensions].
@ Various types of matter: Choquet-Bruhat et al gq/06 [Einstein-scalar].

Types of Spacetimes > s.a. black holes; minkowski [classical stability]; spherical; types of spacetimes [including stationary].
@ Black hole binaries: Pfeiffer et al PRD(02)gq [possible initial data]; Giulini in(03)gq [pedagogical]; > s.a. embedding [diagrams].
@ Asymptotically flat: Penrose PRS(65) [at scri]; Kánnár CQG(00)gq [with Killing vectors]; Valiente Kroon CQG(05)gq/04 [near spi and scri], PRD(05)gq [Schwarzschildean]; García-Parrado & Valiente Kroon PRD(07)gq/06 [Schwarzschild].
@ Conformally flat: Wagh & Saraykar PRD(89); Karkowski & Malec gq/04.
@ Higher-dimensional: Anderson & Tavakol gq/03 [including branes].
@ Other spacetimes and related topics: Beig gq/00-in [Bowen-York initial data]; > s.a. causality violations; constraints; numerical relativity.

Different Approaches and Issues > s.a. [general relativity]; asymptotic flatness; einstein's equation; holography; numerical relativity.
* Possibile variables: ADM, Conformal ADM, Einstein-Bianchi, connection (Ashtekar) variables, ...
* Characteristic problem: A null surface initial-value formulation, with initial data assigned on a null surface.
@ Characteristic problem: Bondi et al PRS(62); Sachs JMP(62), PR(62); Penrose in(64); Müller zum Hagen & Seifert in(79); Penrose GRG(80); Bartnik CQG(97)gq/96 [null quasi-spherical gauge]; Klainerman & Nicolò CQG(99) [double null, vacuum asymptotically flat]; Winicour LRR(98)–LRR(01)–LRR(05); Gómez & Frittelli PRD(03)gq [first-order quasilinear]; Nicolò NCB(04); Frittelli PRD(06) [ADM version of Bondi Sachs]; Caciotta & Nicolò gq/06 [vacuum, small data]; Reisenberger PRL(08)-a0712; > s.a. linearized.
@ Cauchy-characteristic: Gómez et al PRD(96) [for Einstein-Klein-Gordon]; Kánnár PRS(96) [asymptotically characteristic].
@ Initial-boundary: Friedrich & Nagy CMP(99); Szilagyi & Winicour PRD(03)gq/02; Frittelli & Gómez CQG(03), PRD(03)gq, PRD(04)gq/03, PRD(04)gq [boundary conditions]; Kreiss et al CQG-a0707; Friedrich GRG(09)-a0903 [geometric uniqueness]; Winicour GRG(09) [geometric formulation].
@ Mathematical: Beig & Szabados CQG(97)gq [global conformal invariant Y]; Esposito & Stornaiolo gq/00 [and elliptic operators]; Etesi JMP(02)gq/01 [rigidity theorems]; Rendall gq/01-in; Lindblom & Scheel PRD(02) [energy norms and stability]; Dafermos gq/02-in [uniqueness and RN stability]; Karp a0906 [harmonic gauge, well-posedness of problem].
@ Modified ADM formulation: York PRL(99)gq/98, Esposito & Stornaiolo FPL(00)gq, gq/00; Pfeiffer & York PRD(03); Jantzen NCB(04)gq/05 [Taub function = densitized lapse]; > s.a. canonical general relativity.
@ Other formulations: Seriu PRD(00)gq [Laplace eigenvalues]; Bona et al PRD(03) [generally covariant, with vector field Z]; Garfinkle & Gundlach CQG(05)gq [tetrad]; Anderson et al CQG(05) [evolving conformal geometry]; > s.a. Threading.

For Other Theories > s.a. higher-order theories; scalar-tensor theories.
@ Strong coupling limit: Salopek CQG(98)gq, CQG(99)gq/98 [Hamilton-Jacobi].


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