Showing papers on "Gravitation published in 1983"
TL;DR: In this article, a non-trivial analog of gravitation theory in two dimensional spacetime is built upon this fact, with the inverse of the central charge playing the role of the gravitational constant.
1,055 citations
TL;DR: In this paper, it was shown that the five-dimensional Kaluza-Klein theory admits soliton solutions, which are regular, static and stable solutions of the field equations which correspond, upon quantization, to particles.
704 citations
TL;DR: In this article, a complete study of geodesic motion in G\"odel's universe, using the method of the effective potential, is presented, and a clear physical picture of free motion and its stability in this universe emerges.
Abstract: We present a complete study of geodesic motion in G\"odel's universe, using the method of the effective potential. A clear physical picture of free motion and its stability in this universe emerges. A large class of geodesics have finite intervals in which the particle moves back in time ($\frac{\mathrm{dt}}{\mathrm{ds}}l0$) without violation of causality. G\"odel's geometry produces the important property of confinement for a large class of geodesics. We use this property to discuss the construction of a gravitational container. This structure is highly stable, since there is no singularity in its interior, and is independent of the energy of the particles contained in it.
333 citations
TL;DR: In this paper, the thermal structure of nonmagnetic neutron star envelopes is determined by the single parameter T(s to the 4th/g(s), where T is the effective surface temperature and g(s) the surface gravity of the star.
Abstract: The envelopes of nonmagnetic neutron stars are studied using the best available opacities and equation of state. The general relativistic equations of the structure and evolution of nonmagnetic neutron stars are discussed, and it is shown that they can be reduced to a single equation for calculating the thermal structure of neutron star envelopes. The physical input needed to solve the thermal structure equation is investigated and the numerical results of envelope model calculations are presented. It is shown that the thermal structure of neutron star envelopes is determined by the single parameter T(s) to the 4th/g(s), where T(s) is the effective surface temperature and g(s) the surface gravity of the star. This result is used to derive a number of other scaling relations, and the effects of general relativity on the envelope thermal structure are examined in detail. The results of a sensitivity analysis of the regional opacity needed to obtain a reliable relationship between the temperatures of the inner and outer boundaries of the envelope is presented.
287 citations
TL;DR: In this paper, an exact solution of Einstein's equations describing the gravitational field of a plane vacuum domain wall was found, which has event horizons, has no true geometric singularities, and is locally flat everywhere except on the wall itself.
267 citations
TL;DR: In this paper, the authors studied the phenomenon of dimensional reduction in quantum theories of gravity and showed that when the distance around the fifth dimension is larger than the Planck length, the loop expansion is reliable.
Abstract: The phenomenon of dimensional reduction in quantum theories of gravity is studied. In the five-dimensional Kaluza-Klein model, the one-loop effective potential as a function of ${g}_{55}$ is computed. When the distance around the fifth dimension is larger than the Planck length, the loop expansion is reliable. The result leads to a force tending to make the fifth dimension contract to a size on the order of the Planck length. This can be interpreted as a gravitational version of the Casimir effect in electrodynamics.
242 citations
TL;DR: The locally supersymmetric extension of three-dimensional topologically massive gravity is constructed in this article, where the fermionic part is the sum of the Rarita-Schwinger action and a gauge-invariant topological term analogous to the gravitational one.
205 citations
01 Jan 1983
TL;DR: Continuum mechanics is that branch of physics that treats the motions of infinitely deformable matter It embraces hydrodynamics, aerodynamics, magnetohydrodynamisms (MHD), and magnetogasdynamics as mentioned in this paper.
Abstract: Continuum mechanics is that branch of physics that treats the motions of infinitely deformable matter It embraces hydrodynamics, aerodynamics, magnetohydrodynamics (MHD), and magnetogasdynamics The first two differ in that the former is incompressible and the latter compressible fluid dynamics The prefix, magneto, signifies the addition of the ponderemotive force (colloquially called the J-cross-B force) to the usual pressure gradient, gravitational and viscous forces of fluid dynamics Magnetofluid mechanics applies to fluids that can carry electrical currents, such as liquid metals and plasmas Our interest in Solar System MHD is confined to the latter
124 citations
TL;DR: The back-reaction problem for conformally invariant free quantum fields in homogeneous and isotropic spacetime containing classical radiation is solved for spacetimes with nonzero spatial curvatures and/or nonzero cosmological constants.
Abstract: The back-reaction problem for conformally invariant free quantum fields in homogeneous and isotropic spacetimes containing classical radiation is solved for spacetimes with nonzero spatial curvatures and/or nonzero cosmological constants. The solutions depend upon two regularization parameters which we call ..cap alpha.. and ..beta... Only solutions which at late times approach the appropriate solution to the field equations of general relativity are considered. The results are much the same as those found previously for spatially flat spacetimes with zero cosmological constants. Thus, if ..beta..>3..cap alpha..>0, there is always one solution which undergoes a ''time-symmetric bounce'' and which contains no singularities, if ..cap alpha..,..beta..>0 there is a family of solutions with particle horizons and no singularities, and if ..cap alpha..>0 there is always at least one solution with an initial singularity but no particle horizons. The differences caused by the spatial curvature and cosmological constant include the initial behavior of the time-symmetric bounce solution and, if the spatial curvature is nonzero, the initial behavior of many solutions for the cases ..beta.. = 3..cap alpha..>0 and ..beta..roughly-equal3..cap alpha..<0.
121 citations
TL;DR: In this paper, the growth of linear gravitational perturbations in a Friedmann-Robertson-Walker cosmological background is studied in terms of metric perturbation potentials.
Abstract: We elucidate and somewhat extend Bardeen's gauge-invariant formalism for calculating the growth of linear gravitational perturbations in a Friedmann-Robertson-Walker cosmological background. We show that the formalism can be derived from the usual gravitational Lagrangian, by variation with respect to a restricted set of metric perturbation functions. This approach produces a natural decomposition of an arbitrary matter field (whose constitutive equations need not resemble the usual cosmological perfect fluid) into a spatially homogeneous piece, which couples to the background metric, plus a spatially inhomogeneous piece, which is not necessarily small and which is the source term in a second-order differential equation which evolves the gauge-invariant metric perturbation potential. We show how the complete perturbed metric can be reconstructed in arbitrary gauge from the single gauge-independent metric potential, so that the evolution of the matter fields can be concurrently calculated in the usual manner (i.e., in a perturbed coordinate frame). The approach of this paper is designed to be particularly suited to the study of fluctuations generated by classical scalar or gauge fields in "inflationary" cosmological models.
117 citations
TL;DR: In this article, it is pointed out that the path-integral variables as well as the local measure for gravitational interactions are uniquely specified if one imposes the anomaly-free condition on the Becchi-Rouet-Stora supersymmetry associated with general coordinate transformations.
TL;DR: In this article, the teleparallelism theory of gravity is presented as a constrained Poincar\'e gauge theory and arguments are given in favor of a two-parameter family of field Lagrangians quadratic in torsion.
Abstract: The teleparallelism theory of gravity is presented as a constrained Poincar\'e gauge theory. Arguments are given in favor of a two-parameter family of field Lagrangians quadratic in torsion. The inclusion of a "parity violating" term in the field Lagrangian avoids difficulties with the initial-data problem, recently discussed in the literature. Several new exact solutions of the corresponding teleparallelism theory give considerable insight into its physical consequences. The resulting general field equations are analyzed in the weak-field approximation excluding ghosts and tachyons. The physical meaning of the six additional components of the tetrad field (as compared with the metric) appears naturally from our theory and is made clear.
TL;DR: In this paper, a conformal invariant world described by the sum of the Weyl, Dirac, and Yang-Mills action is proposed. But it is not shown that the analogue of the trace anomaly for Weyl action is structurally similar to that for the Yang-mills action.
TL;DR: In this paper, the stability of Poincare × O(3) invariant solutions for Yang-Mills coupled to gravity in 6D space-time compactified over M 4 × S 2 was investigated.
01 Jul 1983
TL;DR: In this paper, a discussion is given of the astronomical implications of a model wherein every elementary particle would have a corresponding mirror (M-) particle of the same mass, and to each interaction (strong, weak, electromagnetic) there would correspond an M-interaction Ordinary (O-) and M-particles could interact essentially only by gravitation.
Abstract: A discussion is given of the astronomical implications of a model wherein every elementary particle would have a corresponding mirror (M-) particle of the same mass, and to each interaction (strong, weak, electromagnetic) there would correspond an M-interaction Ordinary (O-) and M-particles could interact essentially only by gravitation As the model properties are strictly symmetric, so also would be the cosmological evolution of O- and M-matter Qualitative consideration of how M-irregularities would evolve in the early universe suggests that on mass scales M< or approx =10/sup 6/ M/sub sun/ there will be practically no mixing of O- and M-matter except by accretion The model can be tested by improving the observational data on the primordial helium abundance, the missing mass in the galactic disk, and perhaps the nonradial oscillations of the sun
TL;DR: The geometrical structure for a theory of gravitation, based on a nonsymmetric metric in a four-dimensional real manifold, was developed in this article, where the local fiber bundle gauge group is GL(4,R), which contains the (local) homogeneous Lorentz gauge group SO(3,1) of general relativity.
Abstract: The geometrical structure is developed for a theory of gravitation, based on a nonsymmetric metric in a four‐dimensional real manifold. The local fiber bundle gauge group is GL(4,R), which contains the (local) homogeneous Lorentz gauge group SO(3,1) of general relativity.
TL;DR: A survey of theories for the origin of large-scale structure in the universe: clusters and superclusters of galaxies, and vast black regions practically devoid of galaxies is given in this article.
Abstract: A survey is given of theories for the origin of large-scale structure in the universe: clusters and superclusters of galaxies, and vast black regions practically devoid of galaxies. Special attention is paid to the theory of a neutrino-dominated universe—a cosmology in which electron neutrinos with a rest mass of a few tens of electron volts would contribute the bulk of the mean density. The evolution of small perturbations is discussed, and estimates are made for the temperature anisotropy of the microwave background radiation on various angular scales. The nonlinear stage in the evolution of smooth irrotational perturbations in a lowpressure medium is described in detail. Numerical experiments simulating large-scale structure formation processes are discussed, as well as their interpretation in the context of catastrophe theory.
TL;DR: In this paper, the authors considered the initial value problem for the conformally coupled scalar field and higher derivative gravity by expressing the equations of each theory in harmonic coordinates, and showed that the (vacuum) equations can take the form of a diagonal hyperbolic system with constraints on the initial data.
Abstract: The initial value problem is considered for the conformally coupled scalar field and higher derivative gravity, by expressing the equations of each theory in harmonic coordinates. For each theory it is shown that the (vacuum) equations can take the form of a diagonal hyperbolic system with constraints on the initial data. Consequently these theories possess well‐posed initial value formulations.
TL;DR: On montre qu'il y a une acceleration propre possible maximum a 0 relative au vide donnee par a 0 = 2πα (C 7 /¬hG) 1/2.
Abstract: On montre qu'il y a une acceleration propre possible maximum a 0 relative au vide donnee par a 0 =2πα (C 7 /¬hG) 1/2
TL;DR: In this article, the authors analyzed the Newtonian limit of the initial value problem set on a family of null cones and found a simple relationship between the gravitational null data (i.e., the shear of the null cones) and Newtonian gravitational potential.
Abstract: For a general relativistic ideal fluid, we analyze the Newtonian limit of the initial value problem set on a family of null cones. The underlying Newtonian structure is described using Cartan’s elegant space–time version of Newtonian theory and a limiting process rigorously based upon the velocity of light approaching infinity. We find that the existence of a Newtonian limit imposes a strikingly simple relationship between the gravitational null data (i.e., the shear of the null cones) and the Newtonian gravitational potential. This result has immediate application to numerical evolution programs for calculating gravitational radiation and might serve as the basis for a post‐Newtonian approximation scheme.
TL;DR: In this article, the Newman-Penrose formalism is used to work with gravitational, electromagnetic, and Dirac field perturbations of the Kerr-de Sitter space.
Abstract: The Newman-Penrose formalism is used to work with gravitational, electromagnetic, and Dirac field perturbations of the Kerr---de Sitter space. It is shown that the resulting equations are separable, and the radial parts (for the massless fields) combine into a master equation resembling that of Teukolsky. This master equation includes the Teukolsky equation and the equation arising from the de Sitter-Schwarzschild universe, and can be reduced to these cases under appropriate limiting conditions. Finally, the radial parts of the electromagnetic and neutrino fields are transformed to the form of the one-dimensional barrier-penetration equation.
TL;DR: In this paper, the authors discuss the modifications needed to free the Einstein-Hilbert action of gravitation from all second derivatives of fields, and give explicitly the resulting action applicable to either metric or vierbein variables.
Abstract: The authors discuss the modifications needed to free the Einstein-Hilbert action of gravitation from all second derivatives of fields, and give explicitly the resulting action applicable to either metric or vierbein variables. Variation of this action leads to Einstein's equations without boundary conditions. It vanishes for flat space-time and contains one arbitrary real parameter.
TL;DR: The recently proposed inflationary universe scenario as discussed by the authors provides a natural explanation for the origin of time asymmetry (time's arrow) in the universe, which acts as a sort of repulsive gravity.
Abstract: The recently proposed inflationary Universe scenario1–4 explains several of the mysteries of modern cosmology. I argue here that it also provides a natural explanation for the origin of time asymmetry (‘time's arrow’) in the Universe. The new feature which inflation injects into this long-standing problem is the temporary dominance of the cosmological term in the gravitational field equations, which acts as a sort of repulsive gravity. This term generates huge quantities of energy and radiation (or matter) entropy, while drastically reducing the entropy density of the gravitational field. It thus establishes a large gap between the radiation entropy and the gravitational entropy, which gravity is now trying to close.
20 Dec 1983-Philosophical transactions - Royal Society. Mathematical, physical and engineering sciences
TL;DR: In this paper, the solar system data set available at the Harvard-Smithsonian Center for Astrophysics is reviewed, including the measurement of relativistic effects due to the square of the solar potential and the detection of the Lense-Thirring effect.
Abstract: Recent solar system experimental tests of the general relativity theory are reviewed. The solar system data set available at the Harvard-Smithsonian Center for Astrophysics is first reviewed. Investigations of the secular variation of G in the solar system are discussed; recent analyses using Viking data yield G-dot/G of less than 3 x 10 to the -11th/yr. The present data set will make it possible to distinguish between competitive theories. Shapiro's time-delay effect has provided the most stringent solar system test of general relativity. The effect has been measured to be consistent with the predictions of the theory to within an uncertainty of 0.1 percent. Tests which can be performed in the near future, including the measurement of relativistic effects due to the square of the solar potential and the detection of the Lense-Thirring effect, are discussed.
TL;DR: In this article, the authors obtained two scalar-tetradic theories of gravitation from a variational principle, where the gravitational energy is localized and the principle of equivalence holds.
Abstract: In this paper we obtain two scalar-tetradic theories of gravitation (theories A and B) from a variational principle. In these theories the gravitational energy is localized and the principle of equivalence holds. They combine some aspects of M\o{}ller theory and the Brans-Dicke theory. The first-order approximations and an introduction to the study of both theories in the static spherically symmetric case are presented.
TL;DR: In this paper, the effects of gravitation in the collision of two bubbles in the very early universe, using the thin-wall approximation, were investigated, and it was shown that due to the special symmetry of the space-time, the concentration of matter does not suffice to cause any gravitational collapse to a singularity no matter how severely the two bubbles collide.
Abstract: We investigate the effects of gravitation in the collision of two bubbles in the very early universe, using the thin-wall approximation. In general, the collision of two bubbles gives rise to modulus wall and a phase wave. The space-time metric and all physical quantities possess hyperbolic O(2,1) symmetry. We derive a generalized Birkhoff's theorem to show that the space-time in different regions must therefore be flat, de Sitter, pseudo-Schwarzschild, and pseudo-Schwarzschild-de Sitter, respectively. As in the spherically symmetric O(3) case, the space-time is Petrov type $D$, and so there is no gravitational radiation. Owing to the special symmetry of the space-time, the concentration of matter does not suffice to cause any gravitational collapse to a singularity no matter how severely the two bubbles collide. The modulus walls, viewed from the real vacuum region, eventually propagate outwards with kinks due to a series of collisions, in contrast to the situation in the absence of gravity.
TL;DR: In this article, it is argued that the state of an N-particle system may be characterized by an 8N-dimensional phase space, which satisfies a collection of N conservation equations.
TL;DR: In this paper, a non-trivial analog of supergravity in two spacetime dimensions is presented, which results from taking the "square root" of the hamiltonian generators of the model without supersymmetry.
TL;DR: The chaotic behavior of solutions to Einstein's equations has recently been studied by Barrow within the framework of dynamical systems theory as mentioned in this paper, where Quantitative measures of chaos such as the power spectrum and Lyapunov characteristic exponent are computed.
Abstract: The chaotic behavior of solutions to Einstein's equations has recently been studied by Barrow within the framework of the dynamical systems theory. Barrow's program of gravitational turbulence is implemented in part by considering the solutions of type VII/sub 0/ and IX as well as some intermediate types. Quantitative measures of chaos, such as the power spectrum and Lyapunov characteristic exponent, are computed. By converting the equations of motion for the cosmic scale factors to stochastic Langevin's equations, the Mixmaster cosmology in the presence of driving noise terms is investigated. Possible sources of noise can be attributed to an imperfect cancellation of the effective vacuum energy density and the energy density associated with the Higgs field. An ensemble average over random trajectories leads to the suppression of chaotic behavior for type-IX cosmology.