Modern Cosmology |

**General Principles, Status, and Issues** > s.a. anthropic principle;
cosmological constant; holography; references
[including conceptual aspects].

* __Idea__: The study of the properties
of the universe as a whole (observations of the matter and radiation content, distribution
and evolution, as well as other geometry, topology and dynamics of the spacetime itself),
including the early universe.

* __Steps, status__: 1929,
Cosmology becomes a science, based on observation, with Hubble's observation
of the expansion of the universe, and its predictions are subject to
testing; Proposal of hot Big Bang Theory (the name was first used jokingly
by Fred Hoyle in a 1949 BBC broadcast); 1965, Observation of the cmb; 1992,
First COBE results on anisotropy; 1997, First evidence that the expansion is
accelerating, concept of dark energy; 2003, Emergence of "precision
cosmology" with the first WMAP results; 2009, The dominant source of
uncertainty in many observations will soon be cosmic variance as opposed to
observational noise; 2013, Discrepancy between global (cmb) and local measurements
of the Hubble constant and age of the Universe; 2014, Detection of *B*-mode
polarization at angular scales of a few degrees by the BICEP2 cmb telescope.

* __Central dogma__: The same laws
of physics we can test here on Earth apply everywhere in the universe.

@ __Cosmography__: [kinematics of cosmology] Visser GRG(05)gq/04-proc;
Capozziello et al PRD(08).

__Models__:
see cosmological models; cosmological principle;
multiverse cosmology; numerical general relativity;
quantum cosmology.

__Observations__:
see cosmic microwave background; large-scale geometry and topology;
matter content; observational cosmology [including age].

**Other Aspects** > s.a. entropy;
gravitational thermodynamics; Rigidity;
rotation; Superfluids.

* __Cosmic coincidence problem__:
The fact that the densities of vacuum energy and matter are nearly equal today.

* __Measure problem__: The question
of how to assign normalized probabilities to observations; Probabilities are often
invoked, e.g., in the context of inflation, but problems arise for various reasons,
from more formal ones to the fact that such a large universe may have many observations
occurring at many different spacetime locations.

@ __Statistics, number counts__: Colombi et al MNRAS(00)ap/99;
Szapudi et al MNRAS(00)ap/99,
MNRAS(99)ap/99;
> s.a. galaxy distribution.

@ __Complexity and order__: Layzer 89 [I-II];
Hu in(88)gq/95;
Parker 96 [I];
Kunz et al PRD(06) [and parameters];
> s.a. complexity.

@ __Local vs global physics__: Ellis IJMPA(02)gq/01;
Ellis & Stoeger MNRAS(09)-a1001 [local cosmic domain and effective causal limits];
> s.a. arrow of time; Birkhoff's Theorem;
expansion rate [local effects]; mach's principle;
Olbers' Paradox; relativistic cosmology.

@ __Coincidences, tuning, naturality__: & Hoyle;
Carter pr(67)-a0710 [foundation for anthropic principle];
Griest PRD(02) [proposal];
Rees in(03)ap/04;
Carroll Nat(06)apr-ht/05;
França PLB(06),
Funkhouser PRS(06),
PRS(08)phy/06 [proposals];
del Campo et al PRD(08)-a0806;
Barreira & Avelino PRD(11)-a1103 [anthropic vs cosmological solutions];
Sivanandam PRD(13)-a1203
[coincidence is not a problem, just an artifact of anthropic selection];
Carroll a1406-in [fine tuning].

@ __The measure problem__: Page JCAP(11)-a1011;
Schiffrin & Wald PRD(12)-a1202.

**The Future of the Universe** > s.a. Big Crunch;
Big Trip; civilizations
[including Doomsday Argument]; cosmological models.

* __Possibilities__: If the cosmic energy density
will remain constant or strictly increase in the future, the possible fates are:

- __Constant expansion rate__: The Hubble parameter
*H*(*t*) = constant, for example if the energy density is dominated by a cosmological constant.

- __Pseudo-rip__: An intermediate case in which
*H*(*t*) goes to a constant as time goes to infinity.

- __Little rip__: *H*(*t*) goes
to infinity as time goes to infinity.

- __Big rip__: *H*(*t*) goes to
infinity at a finite time and eventually all local structure will be ripped apart by the expansion,
for example in the case of phantom energy.

* __Matter and radiation__: 2007, Krauss & Scherrer
predict matter energy density will keep dominating radiation energy density.

@ __General references__: Davies 94 [I];
Krauss & Turner GRG(99);
Krauss & Starkman SA(99)nov [and life];
Starobinsky G&C(00)ap/99-conf;
Goldsmith 00,
Barrow et al MNRAS(00)ap [including acceleration];
Avelino et al PLB(01) [and inflation];
Tipler AIP(01)ap;
Chiueh & He PRD(02)ap/01 [local structure];
Hoeneisen ap/02;
Ćirković AJP(03)feb-ap/02 [eschatology];
Dąbrowski AdP(06)ap-conf;
Page PRD(08)ht/06 [future decay];
Nicolson 07;
Krauss & Starkman ap/07 [WIMP annihilation];
Carlip JCAP(07)ht [and variation of constants];
Krauss & Scherrer GRG(07)-a0704-GRF [return of static universe],
PRD(07)
+ sr(07)apr [matter domination];
Bose & Majumdar MNRAS(11)-a1010 [future deceleration];
Bousso et al PRD(11)-a1009 [eternal inflation and the end of time];
Lundgren et al a1201 [black hole evaporation and entropy];
Goldsmith SA(12)mar [new phenomena];
Bondarescu et al a1305-MG13.

@ __And dark energy__: Huterer et al PRD(02)ap;
Kallosh et al PRD(02) [supergravity model];
Loeb PRD(02)ap/01;
Adams et al IJMPD(03)ap [island universes];
Kallosh & Linde JCAP(03);
Page JKPS(06)ht/05 [lower limit
26 Gyr, upper limit exp{10^{50}}–exp{10^{60}} yr];
> s.a. dark energy [including late-time interaction].

@ __And astrophysics__: Adams & Laughlin RMP(97)ap [evolution of planets, stars, galaxies];
Loeb JCAP(11)-a1102
+ news pw(11)feb [Milkomeda and the role of hypervelocity stars];
Lundgren et al a1304 [thermodynamics and supercluster evolution];
Guillochon & Loeb AMSA-a1411 [using hypervelocity stars].

@ __Big rip__: Caldwell et al PRL(03)ap;
González-Díaz PRD(03)ap,
PLB(04)ap/03,
PLB(06);
Frampton & Takahashi APP(04)ap,
Frampton ap/04-talk [no dark energy];
Barboza & Lemos GRG(06)gq [and quantum gravity];
Alvarenga et al G&C(10)-a0904 [back-reaction from particle creation];
> s.a. Phantom Field; viscosity.

@ __Other scenarios__: Faraoni PRD(03)gq [big smash, superquintessence]; Frampton et al PRD(11)-a1106 [little rip], PRD(12)-a1112 [pseudo-rip]; Bouhmadi-López et al IJMPD(15)-a1407 [little sibling of the big rip].

What caused the Big Bang? God divided by zero.

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