Modifications of Newtonian Gravity  

In General > s.a. [newtonian gravitation]; covariant quantum gravity; graviton.
* Motivation: Originally (1905) the realization that Newtonian gravitation was incompatible with special relativity; Poincaré made the first attempt to modify the theory; 2001, Interest has increased recently because of proposed higher-dimensional models with 4D spacetime as brane, and to some extent because of possible alternative to dark matter in explanations of galactic dynamics.
* Radial dependence: The only corrections to the potential consistent with relativistic field theory are Yukawa-type,

U(r) = –G mm'/r G (mm'/r) exp{–r/} .

where the range is related to the graviton mass by mg = /c.
@ General articles: Shelupsky AJP(85) [and light bending]; Cook CP(87); Milgrom Rech(88)feb; Parker & Zumberge Nat(89); Onofrio MPLA(98) [motivation and tests]; Mostepanenko gq/03-in [Casimir force].
@ Early work on non-Newtonian effects: Heaviside 1894 [gravitomagnetism]; Forward PIRE(61).
@ Phenomenology: Marinoni & Piazza ap/03/ApJL [GraS]; Dvali ht/04-in [infrared]; > s.a. MOND.
> Phenomenology: see phenomenology of gravity; Sagnac Effect; tests of general relativity; tests of newtonian gravity.

Sources of Corrections > s.a. brane phenomenology; fifth force; higher-dimensional gravity; quantum gravity effects.
@ General relativistic: Iorio GJI(06)gq [on Earth, and possible measurement].
@ Quantum: Donoghue PRL(94); Kazakov CQG(01); Kirilin & Khriplovich JETP(02)gq; Kirillov & Turaev G&C(03)ht/01 [spacetime foam]; Ward IJMPA(05) [resummed quantum gravity]; Bailey & Kostelecky PRD(06)gq [with Lorentz symmetry violation]; Akhundov & Shiekh gq/06 [rev]; Faller a0708 [from effective quantum gravity and scalar QED]; Caldwell & Grin PRL(08) [modifications below 0.05 mm and cosmology].
@ From string theory: Antoniadis hp/99-in; > s.a. string phenomenology.

Parametrized Post-Newtonian (PPN) Formalism > s.a. phenomenology; self-force; tests of general relativity.
* Idea: A framework for comparing general relativity with other metric theories, using 10 parameters which can be experimentally determined; Includes the PN approximation of (nearly) every metric theory.
* Interpretation: For an isolated, spherical object, if represents the non-linearity in gravitational attraction, and the amount of curvature produced by a body,

g00 = –1 + 2U ,   gij = (1 + 2 M/R) ij + ... ,   where   U = M/R (M/R)2 + ...

* Parameter values: 2004, From Cassini data, –1 = (1.2 1.1) × 10–4; 2006, Bounds on and are 10–4–10–5, various missions to improving limits by several orders of magnitude (LATOR, ASTROD, BepiColombo, GAIA) under consideration; 2006, on galactic scales, = 0.98 0.07 (68% cl).
@ General references: in Eddington 22; Robertson in(62); Schiff SIAM(62), in(67); Nordtvedt PR(68), PR(68), PR(69); Will ApJ(71); Will & Nordtvedt ApJ(72); in Misner et al 73, Ch39; Rendall PRS(92); Kopeikin & Vlasov PRP(04) [reference frames, scalar-tensor theory]; Blanchet et al PRD(05)gq [structure, near zone]; Allemandi et al GRG(05)gq [alternative theories].
@ Values: Arminjon gq/03-in [new method]; Bolton et al PRD(06)ap [ on galactic scales]; Alexander & Yunes PRD(07), PRL(07)ht [for Chern-Simons gravity].
@ Effects: Rama & Ghosh PLB(96), same as PLB(96) [values for repulsive gravity]; Schröder & Treder FP(02) [Earth-Moon system]; Arminjon PRD(05)gq, gq/05-in [corrections to equations of motion and new self-acceleration].
@ Variations: Xu & Ma PLB(07) [for 5D gravity, and tests of Kaluza-Klein theory]; Clifton a0801 [for fourth-order theories].
> Related topics: see cosmological models [post-Friedmann framework]; lorentz symmetry phenomenology; motion of test particles and gravitating bodies; sources of gravitational waves; higher-order theories [Newtonian limit]; dark matter; newton-cartan theory.


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