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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.
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26 May 2009
TL;DR: In this article, the authors considered the diffeomorphism invariant gravity coupled with the ideal fluid in a non-standard way and showed that the Lorentz-invariance of the graviton propagator in such a theory considered as perturbation over flat background turns out to be broken due to nonstandard coupling with the perfect ideal fluid.
Abstract: We consider the diffeomorphism invariant gravity coupled with the ideal fluid in the non-standard way. The Lorentz-invariance of the graviton propagator in such a theory considered as perturbation over flat background turns out to be broken due to non-standard coupling with the ideal fluid. As a result the behavior of the propagator in the ultraviolet/infrared region indicates that some versions of such theory are (super-)renormalizable ones (with appearance of only physical transverse modes). The FRW cosmology in same cases may be different from the one in General Relativity with the possible quintessence/phantom-like inflationary stage.
25 citations
TL;DR: In this paper, the authors derived an exact $f(T)$ gravity in the absence of ordinary matter in the Friedmann-Robertson-Walker (FRW) universe, where $T$ is the teleparallel torsion scalar.
Abstract: We derive an exact $f(T)$
gravity in the absence of ordinary matter in Friedmann-Robertson-Walker (FRW) universe, where $T$
is the teleparallel torsion scalar. We show that vanishing of the energy-momentum tensor $\mathcal{T}^{\mu
u }$
of matter does not imply vanishing of the teleparallel torsion scalar, in contrast to general relativity, where the Ricci scalar vanishes. The theory provides an exponential (inflationary) scale factor independent of the choice of the sectional curvature. In addition, the obtained $f(T)$
acts just like cosmological constant in the flat space model. Nevertheless, it is dynamical in non-flat models. In particular, the open universe provides a decaying pattern of the $f(T)$
contributing directly to solve the fine-tuning problem of the cosmological constant. The equation of state (EoS) of the torsion vacuum fluid has been studied in positive and negative Hubble regimes. We study the case when the torsion is made of a scalar field (tlaplon) which acts as torsion potential. This treatment enables to induce a tlaplon field sensitive to the symmetry of the spacetime in addition to the reconstruction of its effective potential from the $f(T)$
theory. The theory provides six different versions of inflationary models. The real solutions are mainly quadratic, the complex solutions, remarkably, provide Higgs-like potential.
25 citations
TL;DR: An exact solution to the Einstein equations with a shear-free imperfect-fluid source that approaches a locally flat Robertson-Walker one in the large-{ital t} limit and thus serves as a viable candidate for a realistic cosmological model.
Abstract: An exact solution to the Einstein equations with a shear-free imperfect-fluid source is obtained. The solution approaches a locally flat Robertson-Walker one in the large-{ital t} limit and thus serves as a viable candidate for a realistic cosmological model. The model built out of this solution is found to be free of horizon, entropy, and flatness problems.
25 citations
TL;DR: In this paper, the authors examined the properties of lattice universes, where point masses are arranged in a regular lattice on spacelike hypersurfaces; open, flat, and closed universes are considered.
Abstract: This paper examines the properties of ``lattice universes'' wherein point masses are arranged in a regular lattice on spacelike hypersurfaces; open, flat, and closed universes are considered. The universes are modeled using the Lindquist-Wheeler (LW) approximation scheme, which approximates the space-time in each lattice cell by Schwarzschild geometry. Extending Lindquist and Wheeler's work, we derive cosmological scale factors describing the evolution of all three types of universes, and we use these scale factors to show that the universes' dynamics strongly resemble those of Friedmann-Lema\^{\i}tre-Robertson-Walker (FLRW) universes. In particular, we use the scale factors to make more salient the resemblance between Clifton and Ferreira's Friedmann-like equations for the LW models and the actual Friedmann equations of FLRW space-times. Cosmological redshifts for such universes are then determined numerically, using a modification of Clifton and Ferreira's approach; the redshifts are found to closely resemble their FLRW counterparts, though with certain differences attributable to the ``lumpiness'' in the underlying matter content. Most notably, the LW redshifts can differ from their FLRW counterparts by as much as 30%, even though they increase linearly with FLRW redshifts, and they exhibit a nonzero integrated Sachs-Wolfe effect, something which would not be possible in matter-dominated FLRW universes without a cosmological constant.
25 citations
TL;DR: In this article, the Friedmann-Robertson-Walker (FRW) cosmological model in the presence of perfect fluid source in gravity was investigated and the physical and kinematical properties of the model were also discussed.
Abstract: In this paper, we investigate Friedmann-Robertson-Walker (FRW) cosmological model in the presence of perfect fluid source in \(f(R,T)\) gravity. We have used linearly varying deceleration parameter proposed by Akarsu and Dereli (Int. J. Theor. Phys. 51:612, 2012) and barotropic equation of state to obtain determinate solution of the field equations of the theory. Physical parameters of the model are determined and some physical and kinematical properties of the model are also discussed.
25 citations