Friedmann–Lemaître–Robertson–Walker metric

About: Friedmann–Lemaître–Robertson–Walker metric is a research topic. Over the lifetime, 4113 publications have been published within this topic receiving 87752 citations. The topic is also known as: FLRW metric.

Cosmological and Black Hole Apparent Horizons

Abstract: Stationary black holes in General Relativity.- Introduction.- Stationary black holes of General Relativity.- Schwarzschild spacetime.- Reissner-Nordstrom metric.- Kerr spacetime.- Kerr-Newman metric.- Energy conditions.- Conclusions.- Problems.- Horizons.- Introduction.- Null geodesic congruences and trapped surfaces.- Rindler horizons for accelerated observers in Minkowski spacetime.- Event horizons.- Killing horizons.- Apparent horizons.- Trapping horizons.- Isolated and dynamical horizons.- Kodama vector and surface gravity.- Surface gravities.- Spherical symmetry.- Rindler horizons revisited.- Conclusions.- Problems.- Cosmological horizons.- Introduction.- . 3.2 Hyperspherical coordinates for FLRW space.- Kruskal-Szekeres coordinates for de Sitter space.- Painlev'e-Gullstrand and Schwarzschild-like coordinates for k = 0 FLRW space.- Schwarzschild-like coordinates for general FLRW spaces.- Painleve-Gullstrand coordinates for general FLRW spaces.- Congruences of radial null geodesics in FLRW space.- Horizons in FLRW space.- Dynamics of cosmological horizons.- Another notation.- de Sitter space.- Thermodynamics of cosmological horizons in General Relativity.- Thermodynamics of de Sitter space.- Thermodynamics of apparent/trapping horizons in FLRW space.- Conclusions.- Problems.- Inhomogeneities in cosmological "backgrounds" in Einstein theory.- Introduction.- Schwarzschild-de Sitter-Kottler spacetime.- McVittie solution.- Charged McVittie spacetime.- An application to the quantization of black hole areas.- Generalized McVittie spacetimes.- Sultana-Dyer spacetime.- Husain-Martinez-Nunez spacetime.- Fonarev solutions.- Other analytic cosmological black hole solutions of the Einstein Equations.- Conclusions.- Cosmological inhomogeneities in alternative gravity.- Introduction.- Brans-Dicke cosmological black holes.- f (R) cosmological black holes.- Conclusions.- A Appendix.- A.1 Painleve-Gullstrand coordinates for general spherically symmetric metrics.- A.2 Kodama vector in FLRW space.- A2.1 Pseudo-Painlev'e-Gullstrand coordinates.- A.2.2 Comoving coordinates.- References.- Index.

Covariant and gauge-independent perfect-fluid Robertson-Walker perturbations.

Abstract: In the preceding paper, covariant and gauge-invariant quantities were defined that characterize density inhomogeneities in an almost-uniform model universe in a transparent way. In this paper second-order propagation equations are derived for these quantities in the case of a general perfect fluid,'' and their properties examined. We do not use a harmonic decomposition in our definitions, but when such a decomposition is applied, our results are compatible with those obtained by Bardeen in his harmonically based gauge-invariant analysis. Our second-order equation enables a unified and transparent derivation of a series of results in the literature, without any ambiguity from choice of any particular gauge.

Quasidilaton: Theory and cosmology

Abstract: General Relativity (GR), with or without matter fields, admits a natural extension to a scale invariant theory that requires a dilaton. Here we show that the recently formulated massive GR, minimally coupled to matter, possesses a new global symmetry related to scaling of the reference coordinates with respect to the physical ones. The field enforcing this symmetry, dubbed here quasidilaton, coincides with an ordinary dilaton if only pure gravity is considered, but differs from it when the matter Lagrangian is present. We study (1) theoretical consistency of massive GR with the quasidilaton; (2) consistency with observations for spherically symmetric sources on (nearly) flat backgrounds; (3) cosmological implications of this theory. We find that (I) the theory with the quasidilaton is as consistent as massive GR; (II) the Vainshtein mechanism is generically retained, owing to the fact that in the decoupling limit there is an enhanced symmetry, which turns the quasidilaton into a second Galileon, consistently coupled to a tensor field; (III) unlike in massive GR, there exist flat FRW solutions. In particular, we find self-accelerated solutions and discuss their quadratic perturbations. These solutions are testable by virtue of the different effective Newton's constants that govern the Hubble expansion and structure growth.

Perturbations of the Robertson-Walker space - Multicomponent sources and generalized gravity

Abstract: Cosmological perturbation equations in the Robertson-Walker background space, considering multicomponent fluid sources with interactions between them, are presented. The perturbation equations, applicable to a class of generalized gravity theories with multicomponent fluids and fields as sources, are generalized. Equations are derived from the covariant equations and presented using the raw kinematic variables of the normal frame with an unspecified gauge. In this way, the equations are easily adaptable to various gauge conditions and also to various gauge-invariant formulations. Relations between different gauges and also to the gauge-invariant formulations are explained