Cosmological Perturbations

General Theory > s.a. chaos in gravitation; cosmological models; perturbations in general relativity [including gravitational waves].
* Motivation: The evolution of cosmological perturbations of an averaged model (Friedmann-Robertson-Walker) allows us to make predictions for structure formation and cosmological radiation backgrounds, that can be checked against observation; The linearized theory can be trusted, because now the perturbations of interest are of order 1, so they must have been small in the past (gravity enhances them in time).
* Idea: They are almost always done around FRW spacetime.
@ Reviews: Mukhanov et al PRP(92); Tsagas ap/02-ln; Brandenberger ht/03-ln, ht/05-ln; Straumann hp/05-ln; Tsagas et al PRP-a0705; Malik & Matravers a0804 [concise intro].
@ Approaches: Unruh ap/98 [long ]; Bertschinger ap/01-in; Bartolo et al PRD(04)ap/03 [scalar + fluid]; Bashinsky PRD(06)ap/04 [cmb and matter]; Carbone & Matarrese PRD(05)ap/04 [evolution framework]; Casadio et al PRD(05)gq/04 [WKB analysis]; Strokov ap/06 [hydrodynamical and field approaches]; Enqvist et al PRD(07)gq [covariant].
@ Non-linear approaches: Matarrese & Pietroni ap/07, JCAP(07)ap, comment Rosten JCAP(08)-a0711 [RG and structure]; Pietroni a0806.
@ Second-order: Malik & Wands CQG(04)ap/03; Bartolo et al JCAP(04) [and non-Gaussianity]; Nakamura PRD(06)gq, PTP(07)gq/06 [gauge-invariant]; Hwang & Noh PRD(07) [second-order].
@ Stability and no-hair: Cotsakis & Miritzis CQG(98) [Bianchi]; Bruni et al CQG(02)gq/01 [FRW metric + dust + cosmological constant]; > s.a. higher-order gravity.
@ Parametric resonance/amplification: Finelli & Gruppuso PLB(01)hp/00 [electromagnetic].
@ Stochastic gravity: Roura & Verdaguer a0709 [correlations and Einstein-Langevin equation]; Urakawa & Maeda PRD(08)-a0710 [inflaton].
@ Related topics: Couch & Torrence CJP(96) [gauging]; Lukash PU(06)ap [tensor and scalar perturbations]; Hwang & Noh a0704 [third-order, pressureless fluids].

Specific Models > s.a. dark energy; dark matter; FRW models; inflation [including lqg].
@ Types of matter: Giovannini CQG(05)ap [imperfect fluid]; Demianski et al GRG(05) [realistic dark energy and dark matter].
@ Various geometries: Moskaliuk et al HJ(95)ap/06 [non-trivial topology]; Calzetta Kandus PRD(97)ap/96 [Tolman universe, non-linear evolution]; Tanimoto CM(03)gq [Bianchi II]; > s.a. bianchi I; bianchi models [III].
@ Origin, quantum cosmology: Halliwell & Hawking PRD(85) [from no-boundary proposal]; Contaldi et al PLB(99)ap; Hofmann & Winkler ap/04 [singularity-free setting]; Bojowald et al PRD(06)gq, PRL(07)gq/06 [lqg]; Sudarsky gq/06-in [critical view, and proposal]; Mielczarek & Szydlowski PLB(07)-a0705 [possible test of lqg].
@ Bounces: Geshnizjani & Battefeld PRD(06)ht/05; Battefeld & Geshnizjani PRD(06); Abramo & Peter a0705 [spectrum unaffected]; Cardoso & Wands PRD(08).
@ Brane world: Aref'eva et al NPB(00); Giddings et al JHEP(00); Langlois PRD(00)ht, PRL(01)ht/00, et al PRD(01)ht/00; Neronov & Sachs PLB(01); Deffayet PRD(02); Leong et al PRD(02)gq/01; Maartens ap/04-in [rev]; Casali et al PRD(04)ht; Cardoso et al JCAP(07)-a0705; Laszlo & Bean PRD(08)-a0709 [non-linear growth]; > s.a. branes.
@ Higher-order gravity: Koivisto & Kurki-Suonio CQG(06)ap/05; Koivisto PRD(06)ap; Song et al PRD(07)ap/06; Bean et al PRD(07)ap/06; Faraoni gq/07/PRD [equivalence to scalar-tensor de Sitter background]; Uddin et al CQG(07)-a0705 [comparison of approaches]; Carloni et al PRD(08)-a0707; Pogosian & Silvestri a0709 [structure growth]; Tsujikawa et al PRD(08)-a0712 [metric and Palatini]; de la Cruz-Dombriz et al PRD(08)-a0802 [metric].
@ Scalar-tensor theories: Carloni et al PRD(06)gq; Carloni & Dunsby PRD(07)gq/06 [tensor perturbations].
@ Effect of electromagnetic fields: Barrow et al PRP(07); Giovannini a0707.
@ Other theories: Cartier et al PRD(01) [string theory]; Linder & Cahn ap/07 [growth of perturbations]; Brandenberger et al a0706 [from a tachyonic big bang]; > s.a. cosmic strings; loop quantum cosmology, MOND/TeVeS, phenomenology of Lorentz violation.

Consequences and Other Issues > s.a. content of the universe; expansion; tests of general relativity; tests with light [deflection].
* Spectrum: 2006, WMAP results show deviations from flat Harrison-Zel'dovich spectrum consistent with inflation [@ news pn(06)mar].
* Back-reaction: The idea is that, to second order in perturbation theory, the first order fluctuations back-react both on the background geometry and on the perturbations themselves.
@ Primordial fluctuations: Matsumiya et al JCAP(03) [from cmb]; Lyth ap/05 [tensor, r < 16 bound]; Armendáriz-Picón JCAP(07)ap/06 [state].
@ Back-reaction: Nambu PRD(02)gq; Brandenberger & Lam ht/04 [and cosmological constant relaxation]; Martineau & Brandenberger PRD(05)ap; Behrend et al a0710-JCAP, Li & Schwarz a0710 [and FRW expansion].
@ Non-Gaussianity: Brown & Crittenden PRD(05)ap [from magnetic fields]; Cooray PRL(06) [21-cm background anisotropy proposal]; > s.a. cmb [Sachs-Wolfe effect].
@ Classicality: Kiefer & Polarski AdP(98)gq [emergence from quantum state]; Lyth & Seery ap/06 [after horizon exit]; Weinberg PRD(06), van der Meulen & Smit JCAP(07)-a0707 [quantum corrections to correlations]; Armendáriz-Picón et al a0805 [limits]; > s.a. early universe, inflation [quantum to classical].
@ And observation: Araújo et al ApJ(01)gq [galaxy redshift and counts]; Zaballa et al JCAP(07)ap/06 [constraints from primordial black holes]; Ferreira & Magueijo a0708 [temperature and fluctuations of early universe]; > s.a. observation [difference between surveys].

Quantum Theory > s.a. quantum gravity effects on cosmology.
* Idea: The quantum theory of cosmological perturbations is trivial, but it is used to give a framework for choosing as initial conditions an appropriate vacuum, like the Bunch-Davies vacuum, a local attractor (because deviations are redshifted away) which gives Gaussian fluctuations.
@ References: Giovannini CQG(03)ht; Peter et al JCAP(05)ht [including quantum backgrounds]; Pinho & Pinto-Neto PRD(07); Campo & Parentani a0805 [decoherence and entropy].

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