Showing papers on "Friedmann–Lemaître–Robertson–Walker metric published in 1984"
TL;DR: The linear perturbation theory of spatially homogeneous and isotropic universes is reviewed and reformulated extensively in this article, with special attention paid to the geometrical meaning of the perturbations.
Abstract: The linear perturbation theory of spatially homogeneous and isotropic universes is reviewed and reformulated extensively. In the first half of the article, a gauge-invariant formulation of the theory is carried out with special attention paid to the geometrical meaning of the perturbation. In the second half of the article, the application of the theory to some important cosmological models is discussed.
1,443 citations
TL;DR: In this paper, it is suggested that the apparent cosmological constant is not necessarily zero but that zero is by far the most probable value, and that the action of solutions of the euclidean field equations is most negative.
474 citations
TL;DR: In this paper, a new class of exact inhomogeneous solutions to Einstein's equations with non-zero cosmological constant and zero pressure was given, which generalize the de Sitter space-time and evolve towards a state that is stationary inside the event horizon of any future inextendible time-like curve and confirm the cosmic no hair conjecture.
145 citations
TL;DR: In this article, a principle of local definiteness is introduced which is needed beyond equations of motion and commutation relations to fix the theory uniquely, and it also allows us to formulate local stability.
Abstract: We discuss quantum fields on Riemannian space-time. A principle of local definiteness is introduced which is needed beyond equations of motion and commutation relations to fix the theory uniquely. It also allows us to formulate local stability. In application to a region with a time-like Killing vector field and horizons it yields the value of the Hawking temperature. The concept of vacuum and particles in a non-stationary metric is treated in the example of the Robertson-Walker metric and some remarks on detectors in non-inertial motion are added.
124 citations
TL;DR: For the class of higher-dimensional Bianchi-Kantowski-Sachs space-times of the Kaluza-Klein type, the authors gave a non-vanishing cosmological constant.
47 citations
TL;DR: In this article, the authors present a classical field theory which has a long epoch resembling the Friedmann universe despite the presence of a large negative cosmological constant in its most plausible realization, which involves a massive third-rank antisymmetric-tensor gauge field.
Abstract: We present a classical field theory which has a long epoch resembling the Friedmann universe despite the presence of a large negative cosmological constant In its most plausible realization the model involves a massive third-rank antisymmetric-tensor gauge field To be consistent with standard cosmology the mass must be extremely small and the only reasonable mechanism for generating it is a semiclassical tunneling effect
46 citations
TL;DR: In this paper, exact solutions of the Einstein field equations for a viscous fluid in which the geometrical part is identical to that of the FRW dust models with k = 0, ± 1 is presented.
22 citations
TL;DR: In this paper, the field equations of general relativity are solved to describe a gravitational field due to a rotating homogeneous fluid in the presence of a Maxwellian source-free electromagnetic field, and it turns out that the metric to describe this field is the well-known Robertson-Walker metric with positive space-time curvature.
Abstract: The field equations of general relativity are solved to describe a gravitational field due to a rotating homogeneous fluid in the presence of a Maxwellian source-free electromagnetic field. It turns out that the metric to describe this field is the well-known Robertson-Walker metric with positive space-time curvature or its particular case, the metric of the closed Einstein universe.
18 citations
TL;DR: In this article, it was shown that the probability density of finding the universe with a radius R vanishes as the classical singularity at R = 0 is approached, and the use of Dirac's method for constrained systems was made and ad-hoc assumptions about the factor ordering problem arising from the classical constraints were avoided.
17 citations
TL;DR: In this paper, a model of higher dimen-sional space-times with an extra space was proposed, whose topology is M2 (2-dimensional space-time)® N n (n-dimertsional external space with a constant curvature k= + 1, 0, -1).
Abstract: ) In order to examine a possibility of incorporating such a unified-field picture into cosmological space times, we shall propose a model of higher dimen sional space-times with an extra space, i.e., whose topology is M2 (2-dimensional space-time)® N n (n-dimertsional external space with a constant curvature k= + 1, 0, -1). We shall further assume that the (2 + n )-dirnensional gravity does not couple with other gauge fields. Taking the above point in view, we shall con sider higher dimensional Einstein equations with a non-vanishing cosmological constant A, i.e.,
15 citations
TL;DR: In this article, a new perfect fluid solution of Einstein's field equations is explicitly given; it is in general of Petrov type II and admits a maximal group of G2 of motions.
Abstract: A new perfect fluid solution of Einstein's field equations is explicitly given; it is in general of Petrov type II and admits a maximal group of G2 of motions. The hypersurface-normal four-velocity is not orthogonal to the group orbits. The equation of state is w=p+constant. The solution can be interpreted as an axisymmetric gravitational field, and appears to represent an inhomogeneous cosmological model. The nature of the singularities is studied.
TL;DR: In this article, the general Brans-Dicke-Friedmann-Robertson-Walker (k=0) vacuum solution with a cosmological constant is presented.
Abstract: We present the general Brans-Dicke-Friedmann-Robertson-Walker (k=0) vacuum solutions with a cosmological constant. The space-times considered here are the generalizations of the de Sitter models of the general theory of relativity.
TL;DR: In this article, a generalization of a class of Szekeres space-times is presented, where the new solutions satisfy Einstein's equations with a cosmological constant.
Abstract: We present a generalization of a class of Szekeres space-times. The new solutions satisfy Einstein's equations with a cosmological constant and have the same geometrical properties as the corresponding class found by Szekeres. Particular cases leading to known solutions are considered.
TL;DR: In this paper, the authors compare three modeles de particules massives de spin 1, dans un espace-temps courbe pour un univers en expansion lente de type Robertson-Walker.
Abstract: On compare 3 modeles de particules massives de spin 1, dans un espace-temps courbe pour un univers en expansion lente de type Robertson-Walker. On effectue la comparaison a l'aide du noyau qui generalise a l'espace-temps courbe le noyau de l'espace plat Δ 1ij (x,y)
01 Jan 1984
TL;DR: In this article, the authors proposed to replace the hypothesis of spatial homogeneity by the assumption that the (matter and radiation) content of the universe is on the average uniform, i.e., the equation of state of the system is everywhere the same.
Abstract: The present standard model of cosmology is based on the cosmological principle which has only limited observational support, especially in connection with the issue of large-scale homogeneity. The recent discovery of voids provides further impetus for the study of large-scale inhomogeneities. It is proposed to replace the hypothesis of spatial homogeneity by the assumption that the (matter and radiation) content of the universe is on the average uniform, i.e., the equation of state of the system is everywhere the same. It has been shown that if (a) the universe is spatially isotropic, (b) the content of the universe is approximated on the average by a perfect fluid obeying a physically reasonable equation of state p = p(μ), including p = O, and (c) the expansion or contraction of the universe is shear-free, then the only physically acceptable nonstatic cosmological solution of the EinsteinMaxwell equations is the Friedmann-Lemaitre-Robertson-Walker (FLRW) universe. If (c) is relaxed, then Einstein’s equations allow solutions which differ from the FLRW models by the existence of radial inhomogeneities due to shear. As a first step toward a general study of inhomogeneities, local models with radial inhomogeneities have been developed and the observational quantities for such models have been determined.
TL;DR: In this paper, the decoupled Dirac equation of the hydrogen-like atom in the Robertson-Walker metric is studied by means of tetrad formalism and energy levels of hydrogen atoms taking into account the cosmological radius are obtained by using the perturbation expansion.
Abstract: The Dirac equation of the hydrogenlike atom in the Robertson-Walker metric is studied in this paper by means of tetrad formalism. The decoupled Dirac equation is derived and energy levels of hydrogen atoms taking into account the cosmological radius are obtained by using the perturbation expansion.
01 Jan 1984
TL;DR: In this paper, the authors recall briefly the "zoology" of dust-filled universes with a positive cosmological constant A. They analyse present observational limits and point out the absence of any convincing argument against a non-vanishing Λ along with important consequences for cosmology.
Abstract: In this paper we recall briefly the “zoology” of dust-filled universes with a positive cosmological constant A. We analyse present observational limits and we point out the absence of any convincing argument against a non-vanishing Λ along with important consequences for cosmology. We present some possible observational tests able to improve existing limits. Finally we mention interesting implications of a positive Λ-term.
01 Jan 1984
TL;DR: In this article, a generalization of the Friedman-Lemaitre -Robertson-Walker (FLRW) models is obtained by weakening the assumptions under which they are derived from Einstein's relativity.
Abstract: A generalization of the Friedman-Lemaitre -Robertson-Walker (FLRW) models is obtained by weakening the assumptions under which they are derived from Einstein’s relativity. It is assumed that each section t = const is homogeneous and isotropic while the spacetime itself not necessarily has any symmetry. The resulting Stephani Universe has an undetermined function of time in place of the constant curvature index k. In this Universe, some spatial sections may be open while others will be closed. Its geometrical picture is presented and its physical properties are discussed.
TL;DR: In this article, the authors considered the non-flatk2=1 Friedmann-Robertson-Walker models with a non-vanishing cosmological constant in the Brans-Dicke theory of gravitation.
Abstract: We consider the non-flatk2=1 Friedmann-Robertson-Walker models with a non-vanishing cosmological constant in the Brans-Dicke theory of gravitation. Some special solutions are given in case of Ω=0, which may be considered as exact solutions of the projective theory of Jordan and Thiry.