Showing papers on "Gravitation published in 1984"
01 Apr 1984
TL;DR: A comprehensive review of the subject of gravitational effects in quantum field theory can be found in this paper, where special emphasis is given to the Hawking black hole evaporation effect, and to particle creation processes in the early universe.
Abstract: This book presents a comprehensive review of the subject of gravitational effects in quantum field theory. Although the treatment is general, special emphasis is given to the Hawking black hole evaporation effect, and to particle creation processes in the early universe. The last decade has witnessed a phenomenal growth in this subject. This is the first attempt to collect and unify the vast literature that has contributed to this development. All the major technical results are presented, and the theory is developed carefully from first principles. Here is everything that students or researchers will need to embark upon calculations involving quantum effects of gravity at the so-called one-loop approximation level.
6,464 citations
TL;DR: In this article, the effects of mass and angular momentum on source-free regions are discussed and some of these effects, especially those generated by mass, angular momentum and mass, are discussed.
1,037 citations
TL;DR: In this paper, a nonrelativistic potential theory for gravity is proposed, which is built on the basic assumptions of the modified dynamics, which were shown earlier to reproduce dynamical properties of galaxies and galaxy aggregates without having to assume the existence of hidden mass.
Abstract: We consider a nonrelativistic potential theory for gravity which differs from the Newtonian theory. The theory is built on the basic assumptions of the modified dynamics, which were shown earlier to reproduce dynamical properties of galaxies and galaxy aggregates without having to assume the existence of hidden mass. The theory involves a modification of the Poisson equation and can be derived from a Lagrangian. The total momentum, angular momentum, and (properly defined) energy of an isolated system are conserved. The center-of-mass acceleration of an arbitrary bound system in a constant external gravitational field is independent of any property of the system. In other words, all isolated objects fall in exactly the same way in a constant external gravitational field (the weak equivalence principle is satisfied). However, the internal dynamics of a system in a constant external field is different from that of the same system in the absence of the external field, in violation of the strong principle of equivalence. These two results are consistent with the phenomenological requirements of the modified dynamics. We sketch a toy relativistic theory which has a nonrelativistic limit satisfying the requirements of the modified dynamics.
887 citations
TL;DR: In this article, it was shown that in a simple minisuperspace model this boundary condition leads to a wave function which can be interpreted as a superposition of quantum states which are peaked around a family of classical solutions of the field equations.
628 citations
TL;DR: In this paper, a nonlinear Schrodinger equation with a self-interacting term was proposed and the separability conditions of Bialynicki-Birula were satisfied in an asymptotic sense.
386 citations
TL;DR: In this paper, for spacetimes of arbitrary dimension, the general two-derivative gravity plus scalar field theory allowing anti-de Sitter space as a solution was considered.
243 citations
TL;DR: In this paper, the authors analyzed unusual features of Einstein's theory of gravitation in a three-dimensional space-time and showed that the standard correspondence of the theory with Newton's theory breaks down.
Abstract: As a preparation for studying quantum models, we analyze unusual features of Einstein's theory of gravitation in a three-dimensional space-time. In three dimensions, matter curves space-time only locally and the gravitational field has no dynamical degrees of freedom. The standard correspondence of Einstein's theory with Newton's theory breaks down. A dust distribution moves without any geodesic deviation between the particles. The cosmological models and relativistic stars behave in a qualitatively different way from their Newtonian counterparts. These features are important for the correct understanding of mini-superspace models.
198 citations
TL;DR: A biomechanical interpretation of point of application of the resultant of ground reactions was presented and the derived equations are useful for processing and interpreting the force platform data.
188 citations
TL;DR: In this article, the authors used the millisecond pulsar 1937 + 21 to predict a stochastic background of gravitational radiation, which should be observable using the pulsar itself.
Abstract: Breaking a Yang–Mills symmetry at very high energy could lead to macroscopic structures in the vacuum called ‘strings’, which may be the cause of galaxy formation and clustering. Dissipative gravitational interactions of string loops can produce unusual astrophysical side effects. Such scenarios generally predict a stochastic background of gravitational radiation which should be observable using the millisecond pulsar 1937 + 21. Gravitational radiation recoil accelerates loops, but dynamical friction on ordinary matter tends to slow them down so they may be able to accrete matter. Internal oscillations of loops produce a time-varying shear perturbation which may lead to an observable heating of stellar or gaseous systems in their immediate neighbourhood.
176 citations
TL;DR: In this article, it was shown that the small nonaxisymmetric distortion of the neutron star should produce some modulation of the X-ray emission at the gravitational wave frequency, and it was hypothesized that this frequency will lie in the 200-800 Hz range.
Abstract: Attention is given to the evolution of neutron stars whose magnetic fields are so weak that (1) the effects of the magnetosphere on the accretion disk are negligible, allowing it to extend to the surface of the star; and (2) the loss of energy and angular momentum by the pulsar mechanism is negligible compared with that provided by the accretion disk. The small nonaxisymmetric distortion of the neutron star should produce some modulation of the X-ray emission at the gravitational wave frequency, and it is hypothesized that this frequency will lie in the 200-800 Hz range. This is significantly below the rotational frequency of the neutron star.
172 citations
TL;DR: In this paper, the authors discuss the quantization of Regge's discrete description of Einstein's theory of gravitation and show how the continuum theory emerges in the weak field long wavelength limit.
Abstract: We discuss the quantization of Regge's discrete description of Einstein's theory of gravitation We show how the continuum theory emerges in the weak field long wavelength limit We also discuss reparametrizations and conformal transformations
TL;DR: In this article, an estimate of the gravitational power spectrum at a point on the Earth is given, where a random gravitational force can be generated by seismic noise, by atmospheric acoustic noise, and by moving massive bodies.
Abstract: A random gravitational force can be generated by seismic noise, by atmospheric acoustic noise, and by moving massive bodies. An estimate of the gravitational power spectrum at a point on the Earth is given. Such a force is an important source of noise in an interferometric gravitational wave antenna below $f=10$ Hz.
TL;DR: In this article, the authors developed a new theory for galaxy clustering in an expanding universe based on the thermodynamics of gravitating systems and applied to the highly nonlinear regime of strong clustering.
Abstract: We develop a new theory for galaxy clustering in an expanding universe. It is based on the thermodynamics of gravitating systems and applies to the highly nonlinear regime of strong clustering. There are no free parameters in the simplest form of this theory. It predicts distribution functions of all orders, from voids to hundreds of galaxies. Comparison of these predictions with the results of numerical N-body experiments shows substantial agreement. Comparison with the observed distribution of galaxies may determine whether it has unrelaxed structure that retains information from much easier epochs of the universe.
TL;DR: The evolution of a universe with π = 1 which becomes dominated by relatively light, non-intercommuting strings at redshift z/sub s/ is similar to that of a matter-dominated universe with Ω(2 + π π + ρ − 1/1/<1) as mentioned in this paper.
Abstract: The evolution of a universe with ..cap omega.. = 1 which becomes dominated by relatively light, non-intercommuting strings at redshift z/sub s/ is similar to that of a matter-dominated universe with ..cap omega..approx.(2+z/sub s/)/sup -1/<1. The existence of such strings can resolve the conflict between the ..cap omega.. = 1 prediction of inflationary cosmology and observations.
01 Jan 1984
TL;DR: In this article, the existence of a singularity at some finite moment of time t = 0 in the past was shown to be a fundamental difficulty in the analysis of the Friedmann-Robertson-Walker cosmological model, and it is shown that the Friedman solution cannot be analytically continued to the region t < 0 where there is no space and no time.
Abstract: The standard Friedmann-Robertson-Walker cosmological model which is widely accepted now provides a good description of the modern state of our Universe, but it encounters a fundamental difficulty, namely, the existence of a singularity at some finite moment of time t = 0 in the past. The Friedman solution cannot be analytically continued to the region t < 0 where, strictly speaking, there is no space and no time. So, in the scope of classical general relativity, it is in principle impossible to ask what was the state of our Universe before t = 0. Thus a bound to the human cognition is set here. The consideration of more general inhomogeneous and anisotropic cosmological models does not improve the situation because, as is well known, these models are also singular.1
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.
TL;DR: In this paper, it was shown that the lattice gravity always approaches the usual continuum limit when the link length l → 0, provided that certain general boundary conditions are satisfied, and this result holds for any lattice, regular or irregular.
TL;DR: In this article, the contribution of a single graviton loop to the quantum effective potential on a background manifold of (Minkowski space) ⊗ (N -sphere) is investigated.
TL;DR: The status of experimental tests of general relativity to the end of 1983 is reviewed in this paper, including the classical tests, tests of the strong equivalence principle and others, and the possibility of using gravitational-wave observations to test metric theories is discussed.
TL;DR: In this article, a model is constructed where a Friedmannian universe, when collapsing, passes the region of Planek's dimensions near the classical singularity in the De Sitter state.
TL;DR: A quasi-Newtonian calculation adapted from Newtonian cosmology suggests that a 'Milgrom universe' will recollapse even if the classical closure parameter Omega is much less than unity as mentioned in this paper.
Abstract: Milgrom's (1983) recent revision of Newtonian dynamics was introduced to eliminate the inference that large quantities of invisible mass exist in galaxies. It is shown by simple examples that a Milgrom acceleration, in the form presented so far, implies other far-reaching changes in dynamics. The momentum of an isolated system is not conserved, and the usual theorem for center-of-mass motion of any system does not hold. Naive applications require extreme caution. The model fails to provide a complete description of particle dynamics and should be thought of as a revision of Kepler's laws rather than Newton's. The Milgrom acceleration also implies fundamental changes in cosmology. A quasi-Newtonian calculation adapted from Newtonian cosmology suggests that a 'Milgrom universe' will recollapse even if the classical closure parameter Omega is much less than unity. The solution, however, fails to satisfy the cosmological principle. Reasons for the breakdown of this calculation are examined. A new theory of gravitation will be needed before the behavior of a Milgrom universe can be predicted.
TL;DR: In this paper, the authors explore the possibility that in N > 4 spacetime dimensions, gravitation is described by a theory based on a modified principle of equivalence, according to which the field equations in locally inertial frames obey a "tangent space" group G T other than the Lorentz group O( N − 1, 1).
TL;DR: In this paper, the renormalization-group equations are given a general formulation in curved space-time and the general form of the equation for the effective charge corresponding to the parameter of nonminimal coupling of a scalar field and the gravitational field is established in the one-loop approximation.
Abstract: This paper presents renormalization-group equations which are given a general formulation in curved space-time. The general form of the equation for the effective charge corresponding to the parameter of nonminimal coupling of a scalar field and the gravitational field is established in the one-loop approximation. It is shown that in the limit of a strong gravitational field the asymptotically free theories can be asymptotically conformally invariant.
TL;DR: In this article, it was demonstrated that plane wave solutions of linearized conformal gravity propagate six physical degrees of freedom, corresponding to massless spin-2 and spin-1 ordibary particles and a massless Spin-2 ghost particle.
TL;DR: In this paper, the foundations of a theory of nonminimal coupling of matter and the gravitational field in the framework of Riemannian geometry are presented, and the theory contains a new parameter l0 of dimension length.
Abstract: The foundations of a theory of nonminimal coupling of matter and the gravitational field in the framework of Riemannian (or Riemann-Cartan) geometry are presented. In the absence of matter, the Einstein vacuum field equations hold. In order to allow for a Newtonian limit, the theory contains a new parameter l0 of dimension length. For systems with finite total mass, l0 is set equal to the Schwarzschild radius.
TL;DR: In this article, the motion of a particle orbiting a planet is investigated when both the gravitational attraction of the planet and the radial radiation force due to the Sun are taken into account.
Abstract: The motion of a particle orbiting a planet is investigated when both the gravitational attraction of the planet and the radial radiation force due to the Sun are taken into account. Because of this latter force, we introduce a rotating frame so as to maintain the Sun at fixed coordinates.
01 Jun 1984
TL;DR: In this paper, the influence of gravitation on quantum field theory was studied, and it was shown that gravity is a background field, changing Minkowski space into a general Riemannian manifold.
Abstract: This is a short survey of results contained in [1]. We study the influence of gravitation on quantum field theory, insofar, that gravity is considered as background field, changing Minkowski space into a general Riemannian manifold. Considerations in this respect were started in [2]. The propagator for the Weyl algebra was found in [3]. Interest in the model increased when in [4] thermal radiation was predicted as consequence of a reasonable state in a Schwarzschild metric (the choice of this state was based on arguments on the time evolution of the black hole). We will restrict the allowed physical states by local conditions and deduce their consequences in the tangent space. They determine already the temperature of the black hole.
TL;DR: In this paper, a prototype of Rastall's theory of gravity, in which the divergence of the energy-momentum tensor is proportional to the gradient of the scalar curvature, is derived from a variational principle.
Abstract: A prototype of Rastall’s theory of gravity, in which the divergence of the energy-momentum tensor is proportional to the gradient of the scalar curvature, is shown to be derivable from a variational principle. Both the proportionality factor and the unrenormalized gravitational constant are found to be covariantly constant, but not necessarily constant. The prototype theory is, therefore, a gravitational theory with variable gravitational constant.
TL;DR: An explicit expression for the quantum gravitational vacuum state by use of the saddle-point approximation and a conformally invariant action was derived in this paper, which consists of a superposition of zero-energy classical vacua that differ in the topology both of the local Lorentz frames and of space itself.
Abstract: An explicit expression is derived for the quantum gravitational vacuum state by use of the saddle-point approximation and a conformally invariant action. It consists of a superposition of zero-energy classical vacua that differ in the topology both of the local Lorentz frames (leading to $\mathrm{CP}$ nonconservation) and of space itself. Space is found to have Planck-size wormholes and spinorial knots, and is surrounded by a vapor of disconnected submanifolds. The scattering matrix constructed on this vacuum is not unitary but the superscattering matrix conserves probability.