Cosmological Constant  

In General > s.a. cosmological constant problem; mach's principle; vacuum.
* History: Introduced by Einstein in 1917 to obtain static universes.
$ Def: A constant representing a vacuum energy density, introduced in the action of general relativity or in the Einstein equation, respectively,

M (R – 2) dv,        Rab R gab+ gab = 8G Tab .

* In quantum field theory: Usually considered to be due to zero-point energy (as pointed out by Zel'dovich in 1968), but in some proposals arises from its fluctuations; Required by symmetry breaking in the early universe, Hawking's picture of spacetime foam, or the gauged SO(n) of extended supergravity.
* In quantum gravity: The ground state for a spacetime with nonzero , to the extent that it is understood, is (Anti-)de Sitter spacetime; A common handwaving argument for the natural value of in quantum gravity is that dimensional considerations lead to lP–2, but arguments of the fluctuation type can also be made assuming that each st element contributes an amount lP–2 to the lagrangian density but with a fluctuating sign.

Consequences and Observation > s.a. black hole radiation; cosmological models; dark energy; quintessence.
* Value: From small clusters of galaxies, |vacuum| = || / 8 < 10–57 cm–2; From the fact that the radius of curvature of the observable universe is basically infinite, < 10–122 lP–2; From 2001 cosmological model, 2.036 10–35 s–2; 2003, WMAP results indicate = LU–2, LU = 2.85 0.25 Mpc, or equivalent amount of dark energy.
@ Measurement: Phillips MNRAS(94); Balaguera-Antolinez et al IJMPD(05)gq/04 [astrophysical bounds]; Vanderveld et al PRD(07)-a0706 [corrections from inhomogeneities]; Chiba & Nakamura a0708-PTP [null test].
@ And lensing: Kochanek ApJ(96)ap/95 [ < 0.66, flat cosmology]; Cheng & Krauss IJMPA(00)ap/98 [0.25 < < 0.55, flat cosmology].
@ And cosmology: in Visser 95 [geometry]; Krauss ap/96 [ < 0], ApJ(98)ap/97, hp/98-in [age of galaxies]; Ishak et al a0710 [lensing].
@ And other astronomy: Sereno & Jetzer PRD(06)ap [solar and stellar systems]; Iorio IJMPD(06), a0710 [solar system]; Erni & Tammann ap/06 [nearby supernovas]; Jetzer & Sereno NCB(07)-a0711-in [solar system].
@ The case for non-zero cosmological constant: Efstathiou et al Nat(90); Krisciunas JRASC(93)ap; Krauss & Turner GRG(95); Ostriker & Steinhardt Nat(95); Roos & Harun-or-Rashid A&A(98)ap/97; Neupane gq/98; Zehavi & Dekel Nat(99)ap; Frampton ap/99-in; Lineweaver ap/99 [obs]; Mannheim ap/99-in, ap/99-in, ApJ(01)ap/99 [conformal gravity]; Carmeli & Kuzmenko ap/01-in, IJTP(02)ap/01 [cosmological model]; Trotta et al PRD(03)ap/02 [Bayesian vs frequentist]; Böhmer ap/05-wd.
@ Consequences of non-zero cosmological constant: Cohn ASS(98)ap; Whitehouse & Kraniotis ap/99 [rotation curves]; Axenides et al MPLA(00)ap [modified motion]; Banks ht/00, GRG(03)ht [susy breaking]; Miguel & Pereira IJMPD(01)gq/00 [speed of light]; Dyson et al JHEP(02)ht [and holography]; Böhmer & Harko PLB(05) [minimum mass]; Balaguera-Antolinez et al CQG(06)gq/95; Nowakowski & Balaguera-Antolinez ap/06-in [in astrophysics]; Peirani & De Freitas A&A-a0806 [galaxy groups].
> Effects: see cosmic acceleration; energy [virial theorem]; galaxy distribution; gravitational phenomenology [PN]; tests of general relativity.

Variable Cosmological Constant > s.a. non-commutative gravity; unimodular gravity; variation of constants.
@ General references: Gasperini PLB(87), CQG(88) [thermal approach]; McGuigan PRD(90) [quantum, from t = (det q)1/2]; van Putten gq/98 [consequences]; Burdyuzha et al ap/99; Novello et al CQG(01)ht/00; Elizalde PLB(01), Caldwell ap/02 [from Casimir effect]; Donoghue JHEP(03) [gradients]; Shapiro et al PLB(03); Hsu & Zee MPLA(05) [Planck mass and size of universe]; Barceló JETPL(07)gq/06; Antoniadis et al NJP(07)gq/06 [dynamical screening by quantum field theory effects].
@ And cosmology: Novello et al CQG(02) [from chiral anomaly]; Aldrovandi et al G&C(05)gq/03; Shapiro & Sola ap/04-in; Borges & Carneiro GRG(05)gq [decaying vacuum density]; Ma a0708 [and constraints].
@ Running, scale dependence: Kosower MPLA(89); Bhattacharya et al PLB(00); Bonanno & Reuter JCAP(07) [from renormalization group, and cosmology]; Foot et al PLB(08)-a0712 [does not run with renormalization scale].
@ From fluctuations: Sorkin IJTP(97)gq; Gurzadyan & Xue MPLA(03)ap/01; Padmanabhan CQG(02)gq, CQG(05)ht/04 [and quantum gravity]; Volovik JLTP(01)gq, in(03)gq; Ahmed et al PRD(04)ap/02, Ahmed IJMPA(05)in [causal sets and statistical fluctuations], comment Volovik JETPL(04)gq and Barrow PRD(07)gq/06; Jejjala & Minic IJMPA(07)ht/06; Elizalde JPA(07) [non-trivial topology and braneworld boundary conditions]; Sorkin a0710-in [causal set discreteness]; Wang et al a0806 [quantum fluctuations of spacetime]; > s.a. cosmic acceleration.
@ From condensate: Dymnikova & Khlopov MPLA(00) [evaporating Bose condensate]; Alexander & Vaid ht/06, ht/07 [chiral fermions in FRW spacetime].

References > s.a. general relativity solutions; higher order gravity.
@ General: Einstein SPAW(17); Hawking in(82), PTRS(83); Banks NPB(85); Coughlan et al NPB(89) [and dilatations]; Strominger NPB(89) [Lorentzian quantum cosmology]; Fiziev gq/00-in [and dilatonic gravity]; Earman SHPMP(03) [conceptual]; Aldrovandi et al IJMPD(04)gq [and fundamental physics]; Bousso a0709-ln.
@ History: Harvey PT(07)apr [Schrödinger and Einstein]; Calder & Lahav a0712 [early precursors, Newton].
@ Reviews: Bernstein & Feinberg ed-89; Weinberg RMP(89), ap/96; Sahni & Starobinsky IJMPD(00)ap/99; Harvey & Schücking AJP(00) [Einstein]; Carroll LRR(01)ap/00; Peebles & Ratra RMP(03)ap/02; Padmanabhan PRP(03)ht/02; Bousso a0708-ln.
@ I: Maddox Nat(89)feb; Mellor SP(89); Goldsmith 95; Krauss & Turner SA(04)sep.
@ And field theory: Schützhold PRL(02) [QCD trace anomaly]; Sundrum PRD(04)ht/03 ["fat" gravity and cosmological constant suppression]; Moffat gq/03 [graviton as bound state], gq/03-in; Mashhoon & Wesson CQG(04)gq [5D]; Mukohyama PRD(04) [radiative corrections and stability]; Blasone et al BJP(05)ht/04 [neutrino mixing]; Volovik JETPL(05)gq-in [from macroscopic parameters]; Mahajan et al PLB(06)ap [Casimir effect: not from zero-point energy]; Ram a0705 [as zero-point energy]; > s.a. brans-dicke, standard model; wormholes.
@ As integration constant: Padmanabhan IJMPD(06)gq; > s.a. modified general relativity, unimodular gravity.
@ Other origin: Jackson & Hogan ht/07 [unconventional quantum spin-statistics]; Pankovic et al a0712 [holography, surface energy density].
@ And higher dimensions: Wesson FPL(06)gq/04 [vacuum instability]; Bauer ht/06-PhD [discrete extra dimensions].
@ And quantum cosmology, Wheeler-DeWitt equation: Garattini gq/04 [as Sturm-Liouville eigenvalue]; Capozziello & Garattini CQG(07)gq [as eigenvalue of Wheeler-DeWitt equation for f(R) theory]; Garattini a0712-in.
@ Related topics: Zel'dovich JETPL(67) [and elementary particles]; Gasperini PLB(89) [and spacetime dimension]; Henneaux & Teitelboim PLB(89) [and time]; Louko CQG(91) [discontinuity at = 0?]; Datta IJMPD(96) [non-gravitating]; Aldrovandi & Barbosa gq/02 [and Lorentz group Casimir]; Aldrovandi et al FP(03) []; Mersini-Houghton gq/06 [arrow of time forbids > 0]; Mazur ap/07 [from "gravitational atoms"]; Lee et al JCAP(07)ht [from entanglement energy].


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