Tests of General Relativity  

In General > s.a. gravitational constant; gravitomagnetism [including brane]; modified general relativity; modified newtonian gravity [PPN].
* Status: 1989, Experimental gravitation is now becoming a major part of general relativity, which is finally recovering a balance between theory and observation; This pushes the theory to justify better its approximations; Also, new tests are being devised, gravitational lensing being one of the most rigorous.
* Types: Weak-field, low-velocity (Solar System tests); Strong-field, low-velocity (binary compact object inspiral); Strong-field, high-speed (binary compact object coalescence); Radiation.
* Solar-system tests: 2014, The two types of tests that have mainly been done so far are weak-field tests in the PPN framework and searches for a fifth force, although spacecraft tracking has been used for tests of the MOND idea and other proposals, and one can constrain Standard Model Extension parameters using Solar System data.
* Bounds on PN parameters: For the non-linearity parameter, β < × 10–3; For the curvature parameter, γ –1 < 10–3 (VLBI and quasars), = (4.8 ± 5.7) × (2.1 ± 2.3) × 10–5 (2003, Cassini spacecraft) [below, η:= 4βγ – 3, and σ = standard error].
* Strong-gravity regime: Two approaches use observations of compact objects and detection of gravitational waves.
@ General references: Møller ed-62; Bertotti ed-74; Will PRP(84); Cook RPP(88); Will Sci(90)nov; Berezin TMP(92); Will IJMPD(92), 93; Karim & Qadir ed-CQG(94); Nordtvedt PT(96)may; Esposito-Farèse in(00)gq/99; Iorio IJMPD(11)-a0908 [bias in some tests]; Morales-Técotl et al ed-10; Tartaglia PoS-a1503; Yunes REF-a1510; Peebles EPJH-a1603 [history, role of Robert Dicke].
@ Reviews: Brill in(73); Damour gq/94, gq/94, in(95), gq/96-proc, gq/97-proc, NPPS(00)gq/99; Will gq/98-ln, LRR(01)gq; Turyshev et al LNP-gq/03; Will pw(05)jan; Ni IJMPD(05)gq; Will LRR(06)gq/05, AdP(06); Bertolami et al gq/06-proc; Turyshev et al IJMPD(07)-a0711, Maleki GRG(08) [space-based research]; Turyshev EPJST(08)-a0804-conf [in space], ARNPS(08)-a0806, PU(09)-a0809; Turyshev in(10)-a0906; Will AJP(10)dec-a1008 [precision tests, RL]; Ni a1204-conf; Bertolami & Páramos a1212 [status]; Hu et al PRD(13)-a1307 [constraints after Planck]; Will LRR(14)-a1403, a1409-in; Baker et al ApJ(15)-a1412 [comparing tests of gravity on all scales]; Asmodelle a1705-BS.
@ Satellite ranging: Giampieri ap/95-proc; Iorio ASR(07)gq/02-conf; Williams et al IJMPD(04), Penanen & Chui NPPS(04)gq [precision].
@ Other solar system tests: Allemandi & Ruggiero GRG(07)ap/06; Iorio PSS(07)gq [effect of Kuiper Belt objects and asteroids]; Wolf et al EA(09)-a0711 [SAGAS project]; Iess & Asmar IJMPD(07) [cosmology-motivated]; Reynaud & Jaekel a0801-ln; Turyshev et al IJMPD(09)-a0805 [BEACON mission]; Jaekel & Reynaud in(07)a0806; Turyshev a0902-rp [opportunities]; Reynaud et al SSR(09)-a0903 [ACES and SAGAS space projects]; Iorio JCAP(11)-a1012, Carloni et al PRD(11)-a1103, Iorio MNRAS(12)-a1108 [and Rindler-type acceleration]; Lenoir et al a1107-conf [Odyssey 2, proposed mission to Neptune and Triton]; Exirifard a1206 [micron-range, near the gravitational saddle point of the Sun-Jupiter system]; Fienga a1209-proc [rev]; Iorio MNRAS(14)-a1307 [tests of gravitational Local Position Invariance]; Hees et al a1403-proc; Iorio IJMPD(15)-a1412 [gravitational anomalies in the Solar System, rev]; Hees a1509-proc [Gaia observations]; Ni a1611-in [rev]; Sakstein a1710 [space-based].
@ Post-Einsteinian framework: Jaekel & Reynaud CQG(05)gq, CQG(06)gq/05; Cornish et al PRD(11)-a1105 [gravitational-wave tests]; Sampson et al PRD(13)-a1307 [connections between the parameterized post-Newtonian, parameterized post-Keplerian, and parameterized post-Einsteinian frameworks]; > s.a. gravitational-wave detection.
@ Clock experiments: Will gq/95; Damour gq/97-proc, gq/99-proc [stringy motivation]; Lichtenegger et al gq/98-conf; Tartaglia CQG(00)gq/99; Schiller et al NPPS(07)gq/06 [in space]; Le Poncin-Lafitte & Lambert ap/06-proc; Bondarescu et al a1412-proc [and interferometers]; > s.a. clocks.
@ Lab experiments: Chen & Cook 93; Barrett gq/97; Zhang et al MPLA(01)gq/00, Iorio CQG(03)gq/02 [rotating bodies]; Dimopoulos et al PRL(07)gq/06 [atom interferometry]; Bimonte et al PRD(08)-a0707 [gravity of magnetic energy and stresses]; Tartaglia et al EPJP(17) [using ring lasers].

blue bullet Main types of tests: see astrophysical and cosmological tests; light deflection; redshift and signal retardation; tests with orbits and spinning bodies.
blue bullet Aspects of gravitational phenomenology: see phenomenology of gravity / equivalence principle; gravitational radiation; gravitomagnetism; lensing.

Effects and Applications > s.a. Aberration; de Sitter-Fokker Precession; gravitational constant.
* Speed of gravity: Based on arrival times of gravitational and electromagnetic signals when the 2017 neutron star merger was detected, the difference between the speed of light and the speed of gravity is less than one part in 1015.
@ Gravitational time dilation: Hafele & Keating Sci(72)jul, Sci(72)jul; Alley in(79); Alberici gq/04, gq/05 [uniform gravitational field]; > s.a. gravitational redshift.
@ Measuring curvature by interferometry: Audretsch & Marzlin PRA(94)gq/93; Snadden et al PRL(98) + news pn(98)jul.
@ Speed of gravity: Novello et al AP(97) [theory with different speed]; Van Flandern PLA(98), comment Marsh & Nissim-Sabat PLA(99), reply PLA(99); Kopeikin PLA(03)gq/02, CQG(04)gq/03; news pw(03)jan; Samuel PRL(03); Will ApJ(03)ap; Fomalont & Kopeikin ApJ(03)ap [Jupiter]; Faber ap/03/ApJL; Asada ap/03-proc; Musser SA(03)apr; Kopeikin & Fomalont PLA(06)gq/03, FP(06)ap/03; Carlip CQG(04)gq [model-dependence]; Samuel IJMPD(04)ap, comment Kopeikin IJMPD(06)gq/05, Asada IJMPD(06), Carlip IJMPD(06); Kopeikin & Fomalont GRG(07) + sr(07)oct [gravitomagnetism and aberration of gravity]; Krasnikov G&C(11)-a1009; Paranjape CJP(13)-a1208 [proposed lab experiment]; Finn & Romano PRD(13) [Rømer time-delay determination]; Collett & Bacon PRL(17)-a1602 [test with strong gravitational lensing]; > s.a. bimetric theory; propagation of gravitational waves.
@ Other topics: Wex IAU-gq/00 [dipole radiation, Stark effect]; Unnikrishnan & Gillies PRD(06), IJMPD(08) [gravity of quantum Fermi pressure].
> On particles and light: see graviton; neutrino; photon; quantum states.

Macroscopic Systems > s.a. neutron stars; phenomenology of gravity.
* GPS: 24 satellites at 12,000 mi + 5 ground stations, operational since 1994; Use two different frequencies, for corrections; Civilian accuracy ≈ 25 m, ≈ 1 m for differential GPS (about $200 by 1995), but ≈ 1 cm is possible.
@ GPS: Kleppner PT(93)apr; Misner gq/95; Herring SA(96)feb; Bahder gq/98 [model-clock behavior in Minkowski], PRD(03)gq; Ashby PT(02)may, LRR(03); Pascual-Sánchez AdP(07)gq/05-conf.
@ Space-based tests: Will Nat(90)oct; Alexeev et al G&C(99)gq/00; Iorio RNC(02)gq/01 [β, γ], JGSJ(02)gq/01 [LAGEOS, Ajisai]; Ni IJMPD(02), et al IJMPD(02) [ASTROD]; Anderson et al gq/03-wd [Cassini]; Lämmerzahl gq/04-MGX; Iorio JCAP(05)gq/04 [of brane-world, comment]; in NPPS(07)166; Appourchaux et al EA(09)-a0802 [ASTROD 1]; Kopeikin PLA(09) [Cassini]; > s.a. tests with orbits [lunar ranging].
@ Other: Longuski et al PRL(01), PRD(04) [spacecraft deflection]; Pascual-Sánchez LNP(03)gq/02 [Earth's gravitomagnetism].

Tests of Other Theories > s.a. gravitational radiation; gravity theories; tests with light [Weyl gravity, light deflection].
@ Fifth force, Yukawa potential: Iorio PLA(02)gq [and LAGEOS]; Bertolami & Páramos IJMPD(11)-a1006 [Galileo satellite constellation].
@ Higher-derivative theories: Accioly & Blas PRD(01)gq [quadratic, light dispersion]; Smith et al PRD(08)-a0708 [Gauss-Bonnet term]; Huang et al a1303 [f(R) gravity, light deflection]; > s.a. higher-order gravity.
@ Brane-world gravity: Ghosh & Raychaudhuri PLB(00), Iorio AdP(12)-a1112 [Randall-Sundrum]; Jalalzadeh et al CQG(09)-a0906, Böhmer et al CQG(10)-a0910 [classical tests].
@ Higher-dimensional theories: Wesson et al MPLA(97), Liu & Overduin ApJ(00)gq [5D, Kaluza-Klein theory]; de Aragão et al gq/05 [and preferred frames]; Rahaman et al IJTP(09)-a0707 [mostly incompatible]; Eingorn & Zhuk a0912, CQG(10)-a1003 [negative result]; > s.a. higher-dimensional gravity; tests with orbits.
@ Other theories: Bailey PRD(09) [Lorentz-violating]; Frye & Efthimiou a1306 [string theory].
> Other theories: see einstein-cartan theory; Gauge Theory of Gravity; Gravity's Rainbow; scalar-tensor theories; torsion.


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