Showing papers on "Friedmann–Lemaître–Robertson–Walker metric published in 1981"
TL;DR: A generalized Robertson-Walker line element with k (t ) is shown to satisfy the Einstein equations with an energymomentum tensor containing a space-like, radial vector of heat flow, which is proportional to the time derivative of k as discussed by the authors.
46 citations
TL;DR: In this article, it has been shown that primordial isothermal perturbations are incompatible with the standard Friedman-Robertson-Walker (FRW) universe for baryosynthesis.
Abstract: In the gravitational instability theory, the present structure in the Universe is envisaged to have evolved from small initial inhomogeneities which are of two generic types: isothermal and adiabatic. It has been shown that in the grand unified theory (GUT) for baryosynthesis primordial isothermal perturbations are incompatible with the standard Friedman–Robertson–Walker (FRW) universe. Here we discuss four non-standard models in which the two are compatible. Of these models two prove to be viable: (1) a universe which is initially dominated by large-scale inhomogeneous shear and (2) a universe which undergoes a de Sitter phase during the GUT phase transition. We also show how to deduce new constraints on chaotic behaviour near the cosmological singularity.
24 citations
TL;DR: Petry as mentioned in this paper applied the theory of gravitation in flat space-time to homogeneous and isotropic cosmological models, and the results showed that these models pass into the homogeneous model of Einstein's theory with spatial curvature equal zero and cosmology constant Λ⩾ 0.
Abstract: A previously studied theory of gravitation in flat space-time [Petry, W. (1981).Gen. Rel. Grav.
13, 865] is applied to homogeneous and isotropic cosmological models. There exist two different classes of models without singularities: (i) ever-expanding models, (ii) oscillating models. The first class contains models with hot big bang. For these models we get at the beginning of the universe—in contrast to Einstein's theory—very high but finite densities of matter and radiation with a big bang of very short duration. After short time these models pass into the homogeneous and isotropic models of Einstein's theory with spatial curvature equal zero and cosmological constant Λ⩾0.
17 citations
TL;DR: In this paper, the authors consider the effect of adding algebraic terms quadratic in the curvature tensor to the usual Einstein-Hilbert action for gravitation, and find that the cosmological solutions of this more general theory are indistinguishable from standard Friedmann models all the way from the initial singularity to the present.
Abstract: We consider the effect on Friedmann cosmology of adding all possible algebraic terms quadratic in the curvature tensor to the usual Einstein-Hilbert action for gravitation. Assuming that the vacuum energy density (cosmological constant) is not extraordinarily large in any phase of the evolution of the universe, we find that the cosmological solutions of this more general theory are indistinguishable from standard Friedmann models all the way from the initial singularity to the present.
16 citations
15 citations
TL;DR: In this article, the diagonal and symmetric Bianchi type IX models are coupled to a homogeneous spinor field, and an action for the combined fields is constructed, where the orthonormal basis used is given explicitly in terms of the metric.
Abstract: The diagonal and symmetric Bianchi type IX models are coupled to a homogeneous spinor field. An action for the combined fields is constructed, where the orthonormal basis used is given explicitly in terms of the metric. This allows one to vary the action with respect to the metric and the spinor fields only. Next, a Hamiltonian formulation is given, and a qualitative solution for the problem is presented. We also show that the k = +1 FRW (Friedmann–Robertson–Walker) model is not compatible with a homogeneous spinor field, while the more complicated models are.
9 citations
TL;DR: In this article, the problem of formulating thermal Green functions for conformally non-invariant field theories in an FRW cosmology was studied and the results made contact with elementary relativistic kinetic theory.
7 citations
2 citations
TL;DR: For the Robertson-Walker metric for a homogeneous and isotropic universe, the authors derived explicit solutions of the Einstein-Yang equation (interior torsion-free solutions for a spinless ideal fluid) and hence found certain solutions for the radiation-dominated phase of the early universe.