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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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TL;DR: In this paper, the authors consider the gravity interacting with matter scalar fields and quantized in the minisuperspace approach in which the wave functional is described by the Wheeler-DeWitt equations.
Abstract: We consider the gravity interacting with matter scalar fields and quantized in the minisuperspace approach in which the wave functional is described by the Wheeler-DeWitt equations (WdW). Assuming the domination of the homogeneous and isotropic geometry the leading contributions to the wave functional in the approximation of the minisuperspace with Friedmann-Robertson-Walker metric (FRW) and spatially uniform scalar fields are considered. The model of several scalar fields with exponential potentials and kinetic terms admitting such a special mixing that ultimately it is possible to separate the variables in the WdW equation and to find its exact solution in terms of the special functions is proposed. The semiclassical approximation is thoroughly investigated and the boundary conditions permitting the physical solution selection for classical cosmologies are chosen.
25 citations
TL;DR: In this article, the cosmological constant is removed from the equations of motion by a nonlocal constraint on the action, which forces the spacetime average of the Lagrangian density to vanish, and a dynamical way for this condition to be satisfied classically with arbitrary matter content.
Abstract: We construct a model in which the cosmological constant is canceled from the gravitational equations of motion. Our model relies on two key ingredients: a nonlocal constraint on the action, which forces the spacetime average of the Lagrangian density to vanish, and a dynamical way for this condition to be satisfied classically with arbitrary matter content. We implement the former condition with a spatially constant Lagrange multiplier associated with the volume form and the latter by including a free four-form gauge field strength in the action. These two features are enough to remove the cosmological constant from the Einstein equation. The model is consistent with all cosmological and experimental bounds on modification of gravity and allows for both cosmic inflation and the present epoch of acceleration.
25 citations
TL;DR: In this paper, the evolution of a two-dimensional minisuperspace cosmological model in classical and quantum levels by the Noether symmetry approach is studied, where the phase space variables turn out to correspond to the scale factor of a Friedmann?Robertson?Walker model and a scalar field.
Abstract: We study the evolution of a two-dimensional minisuperspace cosmological model in classical and quantum levels by the Noether symmetry approach. The phase space variables turn out to correspond to the scale factor of a Friedmann?Robertson?Walker model and a scalar field with which the action of the model is augmented. It is shown that the minisuperspace of such a model is a two-dimensional manifold with a vanishing Ricci scalar. We present a coordinate transformation which cast the corresponding minisupermetric to a Minkowskian or Euclidean one according to the choices of an ordinary or phantom model for the scalar field. Then, the Noether symmetry of such a cosmological model is investigated by utilizing the behavior of the corresponding Lagrangian under the infinitesimal generators of the desired symmetry. We explicitly calculate the form of the scalar field potential functions for which such symmetries exist. For these potential functions, the exact classical and quantum solutions in the cases where the scalar field is an ordinary or a phantom one are presented and compared.
25 citations
TL;DR: In this article, a spherically symmetric structure model in a cosmological background filled with perfect fluid with non-vanishing pressure was constructed as an exact solution of the Einstein equations using the Lemaitre solution.
Abstract: We have constructed a spherically symmetric structure model in a cosmological background filled with perfect fluid with non-vanishing pressure as an exact solution of the Einstein equations using the Lemaitre solution. To study its local and quasi-local characteristics, including the novel features of its central black hole, we have suggested an algorithm to integrate the equations numerically. The result shows intriguing effects of the pressure inside the structure. The evolution of the central black hole within the FRW Universe, its decoupling from the expanding parts of the model, the structure of its space-like apparent horizon, the limiting case of the dynamical horizon tending to a slowly evolving horizon, and the decreasing mass infall to the black hole is also studied. The cosmological redshift of a light emitted from the cosmological structure to an observer in the FRW background is also calculated. This cosmological redshift includes local and cosmic parts that are explicitly separated. We have also formulated a modified NFW density profile for a structure to match the exact solution conditions.
25 citations
TL;DR: In this paper, a cosmological scenario in f ( R, T ) gravity for a flat FLRW model of the universe is considered, in which the model facilitates the formation of structure in the universe according to the Jeans instability condition as our model transits from radiation dominated era to matter dominated era.
25 citations