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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, a modified cosmic Chaplygin cosmology with non-zero cosmological constant in non-flat universe was studied and the authors obtained time-dependent dark energy density by numerical analysis of non-linear differential equation and fitting curves.
Abstract: In this paper we study modified cosmic Chaplygin cosmology with non-zero cosmological constant in non-flat Universe. By using well-known forms of scale factor we obtain time-dependent dark energy density by numerical analysis of non-linear differential equation and fitting curves. We use observational data to fix solution and discuss about stability of our system. First of all we consider cosmological constant as a constant in Einstein equation, and then study possibility of variable cosmological constant.
45 citations
TL;DR: In this article, a class of non-singular bouncing FRW models are obtained by constraining the deceleration parameter in the presence of an interacting dark energy represented by a time-varying cosmological constant.
Abstract: A class of non-singular bouncing FRW models are obtained by constraining the deceleration parameter in the presence of an interacting dark energy represented by a time-varying cosmological constant. The models being geometrically closed, initially accelerate for a certain period of time and decelerate thereafter and are also free from the entropy and cosmological constant problems. Taking a constant of integration equal to zero one particular model is discussed in some detail and the variation of different cosmological parameters are shown graphically for specific values of the parameters of the model. For some specific choice of the parameters of the model the ever expanding models of Ozer & Taha and Abdel-Rahman and the decelerating models of Berman and also the Einstein de-Sitter model may be obtained as special cases of this particular model.
45 citations
TL;DR: In this paper, the authors studied the embedding theory of the gravitation theory in a flat ambient space and showed that the initial conditions for the inflation of the universe can be obtained in the framework of Friedmann-Robertson-Walker (FRW) symmetry.
Abstract: We study the embedding theory being a formulation of the gravitation theory where the independent variable is the embedding function for the four-dimensional spacetime in a flat ambient space. We do not impose additional constraints which are usually used to remove from the theory the extra solutions not being the solutions of Einstein equations. In order to show the possibility of automatic removal of these extra solutions we analyze the equations of the theory, assuming an inflation period during the expansion of the universe. In the framework of Friedmann–Robertson–Walker (FRW) symmetry we study the initial conditions for the inflation, and we show that after its termination the Einstein equations begin to satisfy with a very high precision. The properties of the theory equations allow us to suppose with confidence that the Einstein equations will satisfy with enough precision out of the framework of FRW symmetry as well. Thus the embedding theory can be considered as a theory of gravity which explains observed facts without any additional modification of it and we can use this theory in a flat space when we try to develop a quantum theory of gravity.
45 citations
TL;DR: In this article, the background field method and effective action formalism were applied to describe the four-dimensional dynamical Casimir effect in an expanding FRW universe, where boundary conditions act as a moving mirror and a quantum massless GUT is conformally invariant.
Abstract: We apply the background field method and the effective action formalism to describe the four-dimensional dynamical Casimir effect. Our picture corresponds to the consideration of quantum cosmology for an expanding FRW universe (the boundary conditions act as a moving mirror) filled by a quantum massless GUT which is conformally invariant. We consider cases in which the static Casimir energy is attractive and repulsive. Inserting the simplest possible inertial term, we find, in the adiabatic (and semiclassical) approximation, the dynamical evolution of the scale factor and the dynamical Casimir stress analytically and numerically [for SU(2) super Yang-Mills theory]. Alternative kinetic energy terms are explored in the Appendix. (c) 2000 The American Physical Society.
45 citations
TL;DR: This work explicitly compute the back reaction of the inhomogeneous modes on the minisuperspace sector using a coarse-grained effective action and shows that the min is uperspace approximation is valid only when this back reaction is small.
Abstract: We examine the question of the validity of the minisuperspace approximation using the example of an interacting ({lambda}{Phi}{sup 4}) scalar field in a closed Robertson-Walker universe, where the scale factor and the homogeneous mode of the scalar field model the minisuperspace degrees of freedom. We explicitly compute the back reaction of the inhomogeneous modes on the minisuperspace sector using a coarse-grained effective action and show that the minisuperspace approximation is valid only when this back reaction is small.
45 citations