Modern Cosmological Models

In General, Standard Model > s.a. cosmology [general issues]; observation; general-relativistic cosmology; teaching.
* 1905 situation: There is no galaxy other than the Milky Way, in which stars are distributed with no special pattern; Then there are those funny-looking nebulae, different from star clusters or clouds of hot gas.
* 1920s: Shapley-Curtis debate; Some distant objects behave as if they are moving away fast.
* 1930 models: G Lemaître (relativistic, homogeneous, expanding, constant mass, increasing, r); E A Milne (Euclidean, homogeneous and isotropic, expanding); F Zwicky (non-expanding); Hubble favoured Lemaître.
* Standard cosmological model: Based on general relativity, homogeneity and isotropy as far as geometry goes, and on simplified features of the standard model of matter and interactions, includes (0) A quantum gravity Planck era, (i) A radiation-dominated era (with various possible inflationary variations), (ii) A matter-dominated era and, based on developments since 1997-1998, (iii) A dark-energy dominated era.
* Status: 2004–2006, The general consensus favors a CDM model; Together with a theory of perturbations and baryo- and leptogenesis, explains essentially all observations.
* Issues: 2004–2006, The universe has a "preposterous content", with direct observations accounting for only 1% of total density; Plus, the CDM model has various fudge factors; Could an alternative, "preposterous theory" like MOND, or some other modification of Einstein's gravity, be the way to go? Or could the acceleration be the result of a backreaction to perturbations? How does one carry out the averaging needed to establish a correspondence between the observed universe and a homogeneous one (a.k.a. fitting problem).
@ Standard model: Krauss ap/04-in [dark energy and dark matter]; Scott ap/05-in; Primack NPPS(07)ap/06 [CDM, vs MOND and other issues]; Zhang et al PRL(07)-a0704 [lensing/matter relationship as test for models]; Szydlowski & Tambor a0805 [effective theory, structural stability]; Perivolaropoulos a0811-in [puzzles]; Bartelmann a0906-RMP.
@ Critical views of standard model: Torretti SHPMP(00); Lieu a0705; Sarkar GRG(08)-a0710 [re evidence for dark matter]; Kundt AIP(09)-a0902.
@ Model selection: Liddle et al A&G(06)ap, Liddle MNRASL(07)ap [Bayesian]; Mukherjee & Parkinson IJMPA(08) [rev]; Trotta CP(08)-a0803 [Bayesian, rev]; Linder & Miquel IJMPD(08).

Early-Universe Variations > s.a. entropy; kaluza-klein theory; quantum cosmology.
* Classical modifications: They include oscillating universes and bounces.
* Inflation: Based on a cosmological phase transition as pre-standard model scenario.
* Ekpyrotic cosmology: Based on the brane world as pre-big bang scenario; > s.a. brane cosmology.
@ Origin of universe: Misner PR(69); Rosen AJP(87)jun; Grünbaum PhSc(89)sep, Nat(90)apr; Lévy-Leblond AJP(90)feb; Gott & Li PRD(98)ap/97, Barber gq/02 [self-creation].
> Structure formation: see early-universe cosmology; inflation; cosmological perturbations.

Based on Alternative Theories > s.a. higher-order gravity; Metric-Affine; Non-Symmetric; Riemann-Cartan Structure; scalar-tensor theory.
@ Constraints: Sollerman et al ApJ-a0908 [SDSS-II and other data].
@ Newtonian: Malament PhSc(95)dec; Tipler AJP(96)oct; Ehlers & Buchert GRG(97) [Lagrangian]; Tatekawa et al ap/01 [inhomogeneities]; Zalaletdinov gq/02, gq/02 [averaging]; Romero & Zamora gq/05 [quantum]; Noh & Hwang GRG(06) [non-linear]; Vickers SHPMP(09) [inconsistencies]; > s.a. relativistic cosmology.
@ Quasi-Newtonian: van Elst & Ellis CQG(98) [dust].
@ Post-Newtonian: Rainsford GRG(00)gq/99 [k = 0 FRW model], & Szekeres GRG(00)gq/99; Rainsford GRG(01) [anisotropic].
@ Post-general relativity: Caldwell et al PRD(07)ap [parameter measuring departure from general relativity with cosmological constant].
@ Area-metric cosmology: Schuller & Wohlfarth JCAP(07)-a0705.
@ Related topics: Carmeli 97, IJTP(99)gq [cosmological relativity]; Easson et al PRD(05)ap [quantum-gravity-motivated deformation].
> Related topics: see bimetric theory; brane cosmology; MOND; relativistic cosmology; semiclassical general relativity; variation of constants.

Other Models and Related Issues > s.a. acceleration; quintessence; standard model; Steady State Cosmology.
* Possibilities: Examples of qualitatively different predictions for the evolution of the universe are past-eternal (inflationary versions, steady state), bounce, and cyclic models.
* Island universe: (The name is a reference to Kant's old idea) The universe is initially in a cosmological constant sea, then local quantum fluctuations violating the null energy condition create islands of matter, some of which might correspond to our observable universe.
@ General references: Dyson RMP(79) [and life]; Sandage ARAA(88); Shanks ap/04-in [no dark matter or dark energy]; Barenboim & Lykken JHEP(06)ap [possibilities].
@ Parametrized post-Friedmannian: Tegmark PRD(02)ap/01 [and dark energy]; Hu & Sawicki PRD(07)-a0708; Daniel et al PRD(08)-a0802 [large-scale structure and gravitational slip].
@ Other interpretation of redshift: Gentry MPLA(97), comment Carlip & Scranton MPLA(99)ap/98; Shimizu & Watanabe MPLA(99); Davis & Lineweaver PASA-ap/03 [misconceptions]; Soberman & Dubin a0803.
@ Cyclic models: Kak phy/02 [history in India]; Garriga & Vilenkin PRD(98) [inflationary recycling]; Frampton ap/06-in [dark energy in brane world]; Frampton 09 [I]; Lehners et al a0910-GRF [phoenix universe]; > s.a. cosmological-constant problem; general relativistic models.
@ Island universe: Dutta & Vachaspati PRD(05)ap; Piao PRD(05) [and observations]; > s.a. cosmology [future].
@ Other models: Avelino & Martins PRD(03)ap/02 [classification]; Wanas CSF(03)gq/04 [absolute parallelism]; Vachaspati cm/04-in [condensed-matter experiments]; Schmidt gq/04 [topology/geometry]; Krogdahl gq/04 [flat spacetime]; Puetzfeld NAR(05)gq/04-in [non-Riemannian, rev]; Copeland et al PRD(06)gq/05 [lqc vs braneworld]; Chiba & Takahashi PRD(07) [consistency condition for general relativity]; > s.a. Chameleon Field, FRW models, K-Essence, Milne Universe, Superfluids.
@ Questionable models: Mitchell 02 [Bye Bye Big Bang].
@ Related issues: Nitti et al PRD(05)ht [initial conditions, naturalness]; > s.a. large-scale geometry and topology, multiverse.

"Cosmologists are often wrong, but never in doubt" – L Landau

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