Showing papers on "Gravitation published in 1985"
TL;DR: It is shown that the supersymmetric string theory model has both flat and anti-de Sitter space as solutions, but that the cosmological branch is unstable, because the graviton becomes a ghost there: the theory solves its owncosmological problem.
Abstract: Expansion of supersymmetric string theory suggests that the leading quadratic curvature correction to the Einstein action is the Gauss-Bonnet invariant. We show that this model has both flat and anti-de Sitter space as solutions, but that the cosmological branch is unstable, because the graviton becomes a ghost there: The theory solves its own cosmological problem. The general static spherically symmetric solution is exhibited; it is asymptotically Schwarzschild. The sign of the Gauss-Bonnet coefficient determines whether there is a normal event horizon (for the string-generated sign) or a naked singularity. We discuss the effects of higher-curvature corrections and of an explicit cosmological term on stability.
1,447 citations
TL;DR: In this paper, a constant curvature model for two dimensional space-time, analogous to the theory in three dimensional space time, is proposed, which avoids the triviality of the planar Einstein model by adding sources and a topological mass term.
981 citations
TL;DR: Some discrete lattice models for quantum two-dimensional euclidean gravity are shown to be equivalent to zero-dimensional planar field theories as mentioned in this paper, and a universal continuum limit exists for open surfaces, but not for closed ones.
557 citations
TL;DR: In this article, the (spherical) gravitational shock wave due to a massless particle moving at the speed of light along the horizon of the Schwarzchild black hole is obtained.
488 citations
TL;DR: In this paper, the authors compared the accuracy of the forces derived from several commonly used particle mesh schemes, showing how submesh resolution can be achieved by including short-range forces between particles by direct summation techniques.
Abstract: Techniques for carrying out large N-body simulations of the gravitational evolution of clustering in the fundamental cube of an infinite periodic universe are described and compared. The accuracy of the forces derived from several commonly used particle mesh schemes is examined, showing how submesh resolution can be achieved by including short-range forces between particles by direct summation techniques. The time integration of the equations of motion is discussed, and the accuracy of the codes for various choices of 'time' variable and time step is tested by considering energy conservation as well as by direct analysis of particle trajectories. Methods for generating initial particle positions and velocities corresponding to a growing mode representation of a specified power spectrum of linear density fluctuations are described. The effects of force resolution are studied and different simulation schemes are compared. An algorithm is implemented for generating initial conditions by varying the number of particles, the initial amplitude of density fluctuations, and the initial peculiar velocity field.
476 citations
TL;DR: It is shown that Newton-Cartan theory of gravitation can best be formulated on a five-dimensional extended space-time carrying a Lorentz metric together with a null parallel vector field.
Abstract: It is shown that Newton-Cartan theory of gravitation can best be formulated on a five-dimensional extended space-time carrying a Lorentz metric together with a null parallel vector field. The corresponding geometry associated with the Bargmann group (nontrivially extended Galilei group) viewed as a subgroup of the affine de Sitter group AO(4,1) is thoroughly investigated. This new global formalism allows one to recast classical particle dynamics and the Schroedinger equation into a purely covariant form. The Newton-Cartan field equations are readily derived from Einstein's Lagrangian on the space-time extension.
454 citations
TL;DR: In this article, a discussion of the wave function for an isotropic universe is given, and a logarithmic factor 1 − ln( R R 0 ) is introduced in the gravitational action integral.
426 citations
01 Oct 1985
TL;DR: This chapter discusses the meaning of the metric according to the special theory of relativity and some relations between ordinary and invariant derivatives and the generalizations of Einstein's theory.
408 citations
TL;DR: In this article, it was shown that a gauge theory of self-interacting massless spin-3 particles which is analogous to Yang-Mills or the theory of gravity does not exist.
335 citations
Book•
01 Jan 1985
TL;DR: In this article, the authors divided their book into the following chapters: Geometry and Gravitation, the Formalism of General Relativity, Gravitational Field Equations, Three Classical Tests of Einstein's Theory, Elements of Cosmology, Relativistic Cosmological Models, Non-Static Models of the Universe; Gravitational Waves; Dense and Collapsed Matter; The Einstein-Cartan Theory; The Strong Gravity Theory; Gauge Theory of Gravity; Supergravity, and Gravitational Theory in the Language of Exterior Forms
Abstract: This book is divided into the following chapters: Contents: Geometry and Gravitation; The Formalism of General Relativity; Gravitational Field Equations; The Three Classical Tests of Einstein's Theory; Elements of Cosmology; Relativistic Cosmological Models; Non-Static Models of the Universe; Gravitational Waves; Dense and Collapsed Matter; The Einstein-Cartan Theory; The Strong Gravity Theory; Gauge Theory of Gravity; Supergravity; Gravitational Theory in the Language of Exterior Forms.
167 citations
TL;DR: In this paper, high-speed scattering for a charged particle by a fixed mass and of two uncharged particles of comparable masses is discussed. But the authors do not consider the effect of synchrotron radiation on the motion.
Abstract: After a brief consideration of the high-speed scattering of two point charges we thoroughly discuss high-speed scattering for a charged particle by a fixed mass and of two uncharged particles of comparable masses. We use perturbation technique over Minkowski spacetime in the de Donder gauge and solve the field equations and the resulting equations of motion (which take the reaction of the particles' quasistatic self-field into account) by iteration. The obtained energy-momentum conservation laws allow the computation of second-order corrections for the scattering angle and the cross section. The asymptotic structure of the far-field indicates synchrotron radiation (electromagnetic and gravitational, respectively) which causes an energy loss whose reaction on the motion is briefly considered in the low-velocity limit including bound motion. (For neutral particles this is a third-order effect).
TL;DR: It is pointed out that the electron model of Lopez, which includes spin, and which is a source of the Kerr-Newman field, gives rise to repulsive gravitation.
Abstract: Poincar\'e stresses are explained as due to vacuum polarization in connection with a recently presented class of electromagnetic mass models in general relativity. The gravitational blue-shift of light, noted in an earlier solution of the Einstein-Maxwell equations, is explained as due to repulsive gravitation produced by the negative gravitational mass of the polarized vacuum. It is pointed out that the electron model of Lopez, which includes spin, and which is a source of the Kerr-Newman field, gives rise to repulsive gravitation.
01 Jan 1985
TL;DR: In this article, the main computational methods for obtaining direct solutions of the N-body problem and also to be as complete and self-contained as possible are described, based on the Lagrangian formulation of following the particle motion in detail.
Abstract: Publisher Summary
This chapter describes the direct methods for N-body simulations. Newton's law of gravity imprints its signature on a wide range of scales in the universe, giving rise to a variety of characteristic systems in which the boundary effects are small. Therefore, to a good approximation, the planetary orbits are not affected by the neighboring stars. Likewise, the internal motions of open star clusters are essentially governed by the individual interactions, with the galaxy providing a small external perturbation. The gravitational N-body problem poses a formidable challenge to the numerical analyst. Its nonlinear nature places heavy demands on accuracy considerations, and the need to study large systems over significant times pushes even the biggest computers to their limits. The direct approach is based on the Lagrangian formulation of following the particle motion in detail, as prescribed by Newton's law. Thus, the design of efficient algorithms presupposes some understanding of the problem under consideration, creating a boot-strapping operation. The chapter describes the main computational methods for obtaining direct solutions of the N-body problem and also to be as complete and self-contained as possible.
Book•
22 Apr 1985
TL;DR: The basics The Two-Body Problem Coordinate Systems and Time Systems Corrections to Coordinates Odds and Ends Other Soluble Problems Laplacian-type Initial Orbit Determination Gaussian-Type Initial OrbitDetermination Introduction to PERTurbation Theory More on Perturbation theory Differential Correction Stellar Dynamics Binary Stars as mentioned in this paper
Abstract: The Basics The Two-Body Problem Coordinate Systems and Time Systems Corrections to Coordinates Odds and Ends Other Soluble Problems Laplacian-Type Initial Orbit Determination Gaussian-Type Initial Orbit Determination Introduction to Perturbation Theory More on Perturbation Theory Differential Correction Stellar Dynamics Binary Stars.
01 Jan 1985
TL;DR: The two-dimensional theory of gravity proposed by Jackiw is exactly quantized in the open case and the unique wave functional reflects the classical aspects of the solution.
Abstract: The two-dimensional theory of gravity proposed by Jackiw is exactly quantized in the open case. The Wheeler-DeWitt equation is solved in closed form with and without cosmological constant. The theory has no degree of freedom and the unique wave functional reflects the classical aspects of the solution.
TL;DR: In this paper, a theory of gravity in which the true dynamical variables are the coordinates η a (x ) (a = 1,2,…, N ) of V 4 with respect to M N is presented.
TL;DR: In this paper, a quadratic Lagrangian is proposed for the Riemann tensor, which in dimension greater than four yields second-order field equations and a term which can be used to cancel the vacuum-fluctuation energy and yield a vanishing cosmological constant.
CERN1
TL;DR: With reliance on Regge calculus and the Regge-Einstein action, models of four-dimensional Euclidean gravity are simulated numerically and in the infinite-volume limit, canonical dimensions are realized and a action density is obtained.
Abstract: With reliance on Regge calculus and the Regge-Einstein action, models of four-dimensional Euclidean gravity are simulated numerically. The scale a = 1/sub 0/ is set by fixing the expectation value of a length. Monte Carlo calculations support the following results: In the infinite-volume limit, canonical dimensions are realized and a fi- nite action density is obtained.
TL;DR: In this article, the problem of quantizing an antisymmetric tensor field on a higher-dimensional gravitational background of the form M 4 × S N (where M 4 is an arbitrary 4-dimensional spacetime) is examined, and terms appearing in the effective gravitational action are found for such a theory.
TL;DR: In this paper, an exact solution of the Einstein-Maxwell equations is obtained that represents a space-time which describes consistently the collision between two plane impulsive gravitational waves, each supporting an electromagnetic shock-wave.
Abstract: An exact solution of the Einstein—Maxwell equations is obtained that represents a space-time which describes consistently the collision between two plane impulsive gravitational waves, each supporting an electromagnetic shock-wave. In obtaining the solution, the relationship, which had been established earlier, between the solutions describing stationary black-holes and solutions describing colliding plane-waves, is extended to the Einstein-Maxwell equations (and exploited). The case when the colliding waves are parallelly polarized is analysed in detail to exhibit the singularities and the discontinuities that occur on the null boundaries characteristic of this problem. It is found that the passage of the waves, prior to collision, produces a spray of gravitational and electromagnetic radiation and the collision results in the scattering and the focusing of the waves and the development of a space—time singularity. The solution that is obtained avoids in a natural way certain conceptual difficulties (such as the occurrence of the ‘square root’ of a δ -function and current sheets) that had been anticipated.
TL;DR: In this paper, a procedure for the construction of the gravitational multipoles is proposed, and the full metric is given in the case of a mass possessing a quadrupole moment.
Abstract: A procedure is proposed for construction of the gravitational multipoles. The full metric is given in the case of a mass possessing a quadrupole moment.
TL;DR: In this paper, the scalar potential to two-loop order was shown to vanish for an appropriate redefinition of the potential, and the R -dependence of the β-function for the potential to 2-loop orders was shown.
TL;DR: In this article, the cosmological character of five-dimensional (Kaluza-Klein type) solutions of the Einstein equations was investigated and it was shown that the vacuum solutions of these equations give rise to an effective radiation density connected with the existence of the extra dimension.
TL;DR: In this article, a cosmological constant (Λ) is considered in an isotropic, homogeneous, expanding universe which satisfies the principle of absolute quark confinement, and it is suggested that hadronic matter was created in the early universe as a localized quantum fluctuation of the vacuum.
Abstract: Einstein’s field equations with a cosmological constant (Λ) are explored in an isotropic, homogeneous, expanding universe which satisfies the principle of absolute quark confinement. What emerges from these requirements are new cosmologies free from singularities in physical quantities and with time-varying gravitational (G) and cosmological (Λ) parameters. For the caseG=const and Λ=Λ(t), it is suggested that hadronic matter was created in the early universe as a localized, quantum fluctuation of the vacuum, because |Λ| had an initial value ≈10−10/cm2. The localized fluctuation persisted and evolved into the universe visible today, because |Λ| decreased rapidly with cosmic time. In this sense, «creation» (i.e. «the beginning»)—a manifestly energy-nonconserving event—was linked to a time-varying Λ. which, in turn, was linked to the principle of absolute quark confinement. For the case Λ=Λ(t) andG=G(t), withG, |Λ| larger in the past, the maximum values ofG, |Λ| compatible with absolute quark confinement are those required by the principle of maximum strength,i.e.Gmax≈1040G (whereG=6.67·10−8 dyn cm2/g2) and ¦Λ¦max≈1030/cm2. In spite of the wide variations in the numerical values ofG, |Λ| for both cases, the new cosmologies give the same numerical values for the physical characteristics of the early universe,i.e. maximum hadronic mass density ≈1017 g/cm3, minimum radius ≈1013 cm, maximum temperature ≈1012 K (the limiting temperature for hadronic matter, first noticed by Hagedorn). This circumstance exists because the physical numbers depend only on the ratio |Λ|/G evaluated at cosmic timet=τ (where τ is defined as the «moment of creation»).
TL;DR: In this article, the effective potential for pure gravity in a Kaluza-Klein background geometry was computed in the Lorentz-signature spacetime, avoiding the difficulties of "euclideanization", and it was shown that the contribution of each gravitational degree of freedom to the O(ℏ) part of the potential is significantly greater than that of a scalar or spinor.
TL;DR: In this article, the nodding effect was investigated for the relative motion of neighboring test masses in the field of a rotating mass as well as for the restricted three-body problem in general relativity and the possibility of its detection was briefly discussed.
Abstract: A gyroscope in orbit about a central rotating mass undergoes relativistic nutational oscillations in addition to the well-known precessional motions. The amplitude of the oscillation is proportional to the angular momentum of the rotating mass and its period is the Fokker period of geodetic precession. The amplitude is maximum for a polar orbit and vanishes if the orbit is equatorial. This nodding effect is due to a small divisor phenomenon involving the Fokker frequency, and its existence implies that the applicability of the post-Newtonian approximation of general relativity is limited in time. The dynamical significance of the new effect for the relative motion of neighboring test masses in the field of a rotating mass as well as for the restricted three-body problem in general relativity is investigated and the possibility of its detection is briefly discussed.