|  Perturbations of FLRW Spacetimes | 
In General > s.a. cosmology;
  FLRW models; perturbations in general relativity
  and in quantum cosmology; relativistic
  cosmology [effects].
  * Classification: A convenient
    decomposition of a perturbation is
    \[ a(t)^{-2}\delta g_{ab} = \left(\matrix{\phi & -B_{,i}
    \cr -B_{,i} & \psi\,\delta_{ij} + E_{,ij}}\right)
    + \left(\matrix{0 & S_i \cr S_i & 2\,F_{i,j}}\right)
    + \left(\matrix{0 & 0 \cr 0 & H_{ij}}\right), \]
    respectively a scalar, vector, and tensor perturbation; Here,
    Si and
    Fi are
    divergenceless 3-vectors.
  * Gauge: Four of the
    10 components can be gauged away, and four fixed using constraints,
    leaving two degrees of freedom; For calculations, the longitudinal gauge
    (E = B = Si
    = 0, metric perturbation diagonal) is often convenient, but in terms of physical
    insight the comoving gauge seems to be best.
  * Vector perturbations: 2004,
    Usually dismissed, because they decay (they are a flux, and with the expansion...),
    but the situation is not very clear.
  @ General references: Bardeen PRD(80) [gauge];
    D'Eath AP(76);
    Ellis & Jaklitsch ApJ(89) [constraints];
    Schön PRD(89);
    Ramírez & Kopeikin PLB(02)gq/01 [k = 0 hyperbolic pdes];
    Bičák et al PRD(04)gq/03 [toroidal];
    Durrer LNP(05)ap/04;
    Sharma & Khanal IJMPD(14)-a1109 [in the NP formalism];
    Uggla & Wainwright CQG(12)-a1112 [scalar];
    Pavlov a1601 [intrinsic time];
    Noh et al PRD(20)-a2003 [linearization instability].
  @ Gauge-invariant: Ellis & Bruni PRD(89);
    Ellis et al PRD(89);
    Stewart CQG(90);
    Bombelli et al CQG(94);
    Durrer FCP(94)ap/93;
    Deruelle & Uzan IJTP(97)gq/98 [conservation laws];
    Zimdahl CQG(97) [conserved quantities];
    Kopeikin et al PLA(01)gq [dust, new approach];
    Miedema & van Leeuwen gq/03/CQG,
    a1003-wd;
    Giesel et al CQG(10)-a0711.
  @ Phenomenology: Fanizza et al JCAP(15)-a1506 [light propagation].
  @ Related topics: Bashinsky & Bertschinger PRD(02)ap [dynamics];
    Andersson & Moncrief in(04)gq/03 [global existence];
    Nambu PRD(05)gq [long-λ, back-reaction];
    Bičák et al PRD(07)-a0803 [and local inertial frames];
    Baumann et al JCAP(11)-a1101 [scale-invariant and weakly coupled fluctuations].
Specific Models > s.a. cosmological perturbations
  [including higher-order gravity]; cosmological models.
  @ Exact: Couch & Torrence GRG(96);
    Sopuerta PRD(99) [general, + flat dust models];
    Castagnino et al IJTP(02) [k = 0 + scalar].
  @ Gravitational waves:
    Waylen PRS(78) [in k = −1];
    Couch & Torrence GRG(90),
    GRG(90) [progressing waves].
  @ Bouncing models: Brandenberger et al PRD(02) [trans-lP physics];
    Gordon & Turok PRD(03);
    Martin & Peter PRD(03)ht,
    PRL(04)ap/03,
    PRD(04)ht,
    gq/04;
    Deruelle & Streich PRD(04)gq;
    Deruelle gq/04;
    Gasperini et al NPB(04);
    Allen & Wands PRD(04);
    Pinto-Neto IJMPD(04)ht;
    Battefeld & Geshnizjani PRD(06)ht/05;
    Creminelli et al PRD(05);
    Cardoso & Wands PRD(08).
  @ With varying constants: Barrow & Mota CQG(03)gq/02 [varying α].
  @ Other models: Hwang & Noh CQG(02)ap/01 [multiple fields];
    Khoury et al PRD(02)ht/01 [ekpyrotic];
    Ullrich MS(07)-a0709 [fluids + cosmological constant].
Non-Linear, Second-Order
  @ General references: Reula PRD(99)gq [exponential decay];
    Mena et al IJMPA(02)gq-in [+ cosmological constant];
    Noh & Hwang PRD(04)ap/03 [+ cosmological constant];
    Langlois & Vernizzi PRL(05)ap [fully non-perturbative].
  @ Gauge-invariant: Clarkson PRD(04) [and waves];
    Bartolo et al JCAP(04)ap/03 [non-Gaussianity];
    Nakamura gq/06-proc.
  @ Localized: Wilson & Dyer GRG(07) [spherically symmetric overdense galaxy-like region].
 main page
  – abbreviations
  – journals – comments
  – other sites – acknowledgements
  send feedback and suggestions to bombelli at olemiss.edu – modified 17 jul 2020