|  de Sitter Spacetime | 
In General
  > s.a. anti-de sitter space; ads-cft
  [including dS-cft]; cosmological constant.
  $ Def: A cosmological solution
    of Einstein's equation with positive cosmological constant (for Λ < 0,
    see > anti-de sitter spacetime), and line element
ds2 = −dt2 + H−2 cosh2(Ht) dΩ32, with H 2 = Λ/3 , amin = H−1 = (3/Λ)1/2,
    the geometry of a Lorentz hyperboloid in 5D Minkowski space;
    The symmetry group is SO(4, 1) (de Sitter group).
  * Topology: \(\mathbb R\)
    × S3, spatially compact [@ Mitskevich
    & Senin SPD(82)].
  * Infinity:
    \(\cal I\)± are spacelike;
    The spacetime has future and past event and particle horizons.
  @ General references: in Schrödinger 56;
    Spradlin et al ht/01-ln;
    Bousso ht/02-fs [quantum aspects];
    Kim et al ht/02 [classical, rev];
    Schmidt AHA(05)gq [history];
    Cuzinatto et al AJP(11)jun-a1009 [Lenz-Sommerfeld-type argument].
  @ Geometry:
    Parikh PLB(02) [new coordinates];
    Kasedou JGP(10) [spacelike submanifolds of codimension 2];
    Anninos et al CQG(11) [asymptotic symmetries and charges at null infinity];
    Pascu a1211 [common coordinate charts];
    Tod a1505 [and Penrose's quasi-local mass];
    > s.a. coordinates [Fermi normal coordinates].
  @ In quantum gravity:
    Bousso PRD(99) [1-loop];
    Witten ht/01-conf;
    Klemm & Vanzo JCAP(04)ht ["quantum gravity in de Sitter space"];
    Giddings & Marolf PRD(07)-a0705;
    Einhorn & Jones JHEP(17)-a1606 [zero modes in metric conformal fluctuations];
    Brahma et al a2007 [as a coherent state];
    > s.a. quantum cosmology.
  @ Related topics: Parikh et al PRD(03)ht/02 [elliptic, dS/\(\mathbb Z\)2];
    Aledo & Romero DG&A(03) [3D, compact space];
    McInnes JHEP(03)ht [S3 vs \({\mathbb R}{\rm P}^3\)];
    Mbarek & Paranjape PRD(14)-a1407 [negative-mass bubbles];
    Nouri-Zonoz et al PRD(15)-a1409 [with dark fluid or cosmological constant];
    Russo & Townsend a1904
      [compactification from D > 4 dimensions to de Sitter space];
    > s.a. Hypersurfaces.
  > Online resources:
    see Wikipedia page.
Phenomenology
  > s.a. fields and particles in de sitter spacetimes; inflation;
  kinematics in special relativity [twin paradox]; radiation.
  * Entropy: It can be associated
    with the horizon, and in 2+1 calculated using Carlip's SL(2, \(\mathbb C\))
    Chern-Simons theory method.
  @ Thermodynamics:
    Maldacena & Strominger JHEP(98) [entropy];
    Wang & Huang MPLA(01) [path-integral approach];
    Danielsson & Olsson JHEP(04)ht/03 [thermalization];
    Takook AP(16)-a1306 [entropy of quantum fields];
    Ulhoa & Spaniol JoG(16)-a1312 [entropy];
    Podolskiy a1801 [entropy, from soft states].
  @ Stability:
    Abbott & Deser NPB(82) [canonical];
    Faraoni PRD(05)gq,
    Faraoni & Nadeau PRD(05)gq [in modified gravity and scalar-tensor];
    Faraoni & Jensen CQG(06)gq [criterion, and dark energy/scalar-tensor gravity];
    Parikh PRD(11)-a0909 [increased instability in Einstein-Gauss-Bonnet theory];
    Copsey & Mann PRD(10)-a1001 [higher odd-dimensional, non-Kaluza-Klein bubbles of nothing];
    Huang et al MPLA(10)-a1003 [in Hořava gravity];
    Bander PRD(10)-a1003 [2D, with interacting fields];
    Cognola et al a1006-MG12,
    PRD(11) [in modified gravity];
    Mena JPA(10)-a1006 [second-order perturbations of dust solution];
    Elizalde et al PRD(12)-a1110,
    PoS(11)-a1202 [in non-local cosmological models];
    Anderson & Mottola PRD(14)-a1310,
    PRD(14)-a1310
      [global de Sitter space is unstable even for a massive free field theory];
    > s.a. modified gravity;
      semiclassical gravity; vacuum energy.
  @ Quantum instability: Ho & Hsu JHEP(15)-a1501;
    Rajaraman PRD(16)-a1608;
    Matsui JCAP(19)-a1806 [from the conformal anomaly, below the Planck Scale].
  @ Analogs in condensed matter: Fedichev & Fischer PRL(03)cm [and Hawking radiation];
    Weinfurtner GRG(05)gq/04-conf.
Asymptotically de Sitter Spacetimes
  > s.a. black-hole solutions; gravitational-wave
  propagation; gravitational-wave solutions.
  @ General references: Friedrich JGP(86);
    Firouzjahi & Leblond JCAP(03)ht/02 [and aAdS];
    Faraoni PRD(04)gq [de Sitter as attractor for gravity theories];
    Galloway CM-gq/04-conf [conformal infinity and singularities];
    Lübbe & Valiente Kroon CQG(09)-a0903 [existence];
    Anninos IJMPA(12)-a1205 [overview of some issues];
    Ashtekar et al CQG(14)-a1409
    + CQG+ [basic framework for asymptotics];
    Kastor et al CQG(17)-a1608 [asymptotically future de Sitter];
    Aneesh et al CQG(19)-a1902 [conserved charges];
    Ashtekar & Bahrami PRD(19)-a1904 [the 'no-incoming radiation' condition];
    Fernández-Álvarez & Senovilla a2105 [asymptotic structure, new approach].
  @ Mass, energy: Kastor & Traschen CQG(02)ht [positive energy];
    Dolan a1808;
    Almaraz & Lopes de Lima a1811.
  @ And matter fields: Medved CQG(02)ht [with dust, and holography];
    Leblond et al JHEP(03)ht/02 [massive scalar fields];
    Meissner a0901 [with point mass];
    Ashtekar et al PRD(15)-a1506.
  @ Stability: Bruni et al CQG(02) [second-order perturbations of FLRW spacetimes].
  > Related topics: see
    Alexandrov Sets and causal structures [volumes of causal
    intervals]; multipole moments; Quadrupole Formula.
Other Similar Spacetimes and Generalizations
  > s.a. differential geometry [fuzzy de Sitter];
  higher-order theories.
  @ References: Giambò CQG(02) [anisotropic matter];
    Schleich & Witt CJP(08)-a0807,
    Randono CQG(10)-a0909 [locally de Sitter spacetimes];
    Minkevich MPLA(11)-a1002 [with torsion];
    > s.a. modified general relativity [de Sitter tangent group];
      solutions of general relativity [topology].
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