Gravitational Radiation  

In General > s.a. detection [motivation for search]; graviton.
* Idea: Wavelike solutions of the linearized Einstein equation, propagating at the speed of light; Ripples in a reference spacetime.
* History: 1918, Einstein showed that the linearized equation admits such solutions; Many believed that they would not carry energy/momentum, although calculations showed they would; 1936, Einstein, Infeld & Rosen state that there are no gravitational waves, based on the belief that such solutions are singular; 1949, Landau pseudotensor; 1950s, Bondi, Feynman argue that gravitational waves carry energy; 1970s, Weber's bar detector; 1980s, Thorne, Damour, well-defined framework.
* Evidence: 1999, Indirect, from the increase of the binary pulsar period (75 × 10–6 sec/yr); 2005, Better binary pulsar.
* Significance: Their existence supports the idea that spacetime is a real, physical entity, like water in a pool.

Theory > s.a. gauge invariance; orbits of gravitating bodies [with radiation]; propagation.
* Properties: Contrary to the previous opinion of some people, it carries energy and momentum (see news tensor, Bondi mass, etc); Even perturbatively, tmn(1) 0 for + and × polarizations; It has spin 2, as can be seen from (a) Linearization of the Einstein equation around gab = ab; In the weak field limit the spin appears as the eigenvalue of the corresponding Casimir operator; (b) Study of the asymptotic theory, for which the Poincaré group is an exact symmetry group.
* Characterization: A useful tool is the study of the spin coefficients in the Newman-Penrose formalism, or the Beetle-Burko radiation scalar, all constructed using the Weyl tensor (> see spin coefficients, weyl tensor).
* Open questions: Do general solutions have the falloff required by the scri formalism? One does not start from Cauchy data and construct full solutions; An important thing is to try to remove symmetry requirements.
@ Properties: Walker & Dual gq/97 [longitudinal, near field]; Aldrovandi et al FP(07)-a0709 [importance of non-linearity].

Quadrupole Formula and Energy Loss > s.a. brane phenomenology; multipoles.
* Assumptions: Velocities are small, and T00 dominates the stress-energy tensor.
* Formula:

–dE/dt = i,j = 13 (G/45c5)(d3Qij /dt3)2,   Qij = d3x (x) (3 xi xj – ij r2) .

@ References: in Misner et al 73; Ehlers et al ApJ(76) [controversy]; Walker & Will PRL(80); in Wald 84; Winicour GRG(87); Helfer PRD(93).

Types and Effects > s.a. angular momentum; background; early universe; propagation and sources; thermodynamics.
@ Polarization: Canfora et al PLB(02) [non-linear waves].
@ Energy-momentum: Abramo PRD(99)ap [very long wavelength]; Cooperstock AP(00)gq/99, MPLA(99)gq ["no E"]; Garecki AdP(02)gq/01; Sharif NCB(01)gq, IJMPA(02)gq/01 [example]; Dereli & Tucker CQG(04) [energy-momentum density]; Mannheim PRD(06)gq [covariant]; Ruiz et al a0707 [multipole expansion].
@ Background-independent: Agresti et al GRG(04)gq/03, gq/03; Lusanna gq/04-in, gq/04-in.
@ Related topics: Schmidt PRS(87) [near infinity]; Burnett JMP(89) [high-f limit]; van Putten & Eardley PRD(96)gq/95 [as Yang-Mills waves]; Esposito CQG(01)gq [Green functions]; Stewart GRG(06) [shock waves]; Deffayet & Menou ApJL(07)-a0709 [spacetime sirens as probes of new gravity]; > s.a. chaotic motion.
> Types: see gravitational wave solutions; petrov-pirani classification.

References > s.a. canonical quantum gravity; Penrose Inequality; quantum gravity phenomenology; stress-energy pseudotensor.
@ Intros, reviews: in Heaviside 1894 [precursor]; Weber 61; Pirani in(65); Hawking CP(72); in Misner et al 73; Zakharov 73; Walker in(83); Schutz AJP(84), gq/00-in; Damour in(87); Thorne 91, in(95); Will PT(99)oct [as tests of general relativity]; Blanchet LNP(00)gq-in [post-newtonian]; Hughes AP(03)ap/02; Centrella AJP(03)RL-gq/02; Sathyaprakash gq/04-in; Flanagan & Hughes NJP(05)gq; Maggiore gq/06-in, 07; Kennefick 07; Buonanno a0709-ln; Maggiore 08.
@ Conferences: Smarr ed-79; Królak ed-97; Ciufolini et al ed-00; issue CQG(02)#7 [Amaldi 4]; issue CQG(03)#17 [analysis 7]; issue CQG(04)#5 [Amaldi 5]; issue CQG(04)#20 [analysis 8]; issue CQG(06)#8 [Amaldi 6]; issue CQG(07)#19 [analysis 11]; issue CQG(08)#11 [Amaldi 7]; > s.a. interferometers.
@ General references: Weber & Wheeler RMP(57); Bondi et al PRS(62); Sachs PR(62), PRS(62); Komar PR(64); Van der Burg PRS(66); Blanchet & Damour PTRS(86); Friedrich CMP(86); Blanchet PRS(87); Bondi & Pirani PRS(89); Blanchet et al LNP(01)gq/00.
@ "Non-existence": Denisov & Logunov TMP(80); Burdet & Perrin LMP(92) [gravitons]; Loinger ap/98, ap/99, ap/99, ap/99/NCB, ap/99/NCC, NCB(00)ap, gq/00 [v of thought!]; Marshall a0707.
@ And quantum theory: Ashtekar PRL(81), JMP(81), in(81) [asymptotic quantization]; Manoukian GRG(90); Lovas HIP(01)gq/99.

In Other Theories > s.a. brans-dicke; higher-dimensional; scalar-tensor.
* Idea: Some predict 3 transversal modes, and 3 longitudinal ones.
@ mgrav > 0: Loskutov TMP(96); Will & Yunes CQG(04)gq [and LISA].
@ Higher-order gravity: Ananda et al PRD(08)-a0708 [cosmological]; Desai et al a0805; > s.a. phenomenology.
@ Related topics: Durrer & Kocian CQG(04) [higher-dimensional, quadrupole formula and binary pulsar]; Canfora et al IJGMP(06) [spin-1].

Online Resources > see Thorne et al Caltech 2002 web-based course; The Gravitational Lens newsletter.

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Send feedback and suggestions to bombelli at olemiss.edu – Modified 5 jul 2008