Limiting behavior of asymptotically flat gravitational fields

Couch and Torrence suggest that the vacuum Einstein equations admit a larger class of asymptotically flat solutions than those exhibiting the peeling property. Starting with the assumption that , (d/dr) and (/x ^A ) , wherex ^A (A = 2, 3) are angular coordinates, they show that , where ₁ 2 and ₁<₀; , where ₂ 1 and ₁< ₁; and ₄ and ₃ peel as they would under the stronger peeling conditions. The Winicour-Tamburino energy-momentun and angular momentum integrals for these solutions, in general, diverge. In fact, since Couch and Torrence determine only the radial dependence of the solution, it is not clear that the solutions are well defined. We find that the stronger assumption , (d/dr) , and (/x ^A ) does result in well-defined solutions for which both the energy-momentum and angular momentum intergrals are not only finite but result in the same expressions as are obtained for peeling space-times. This assumption appears to be the minimal assumption that is necessary for investigating outgoing radiation at null infinity.In part based on a dissertation by Stephanie Novak and submitted to Syracuse University in partial fulfillment of the requirement for the Ph.D. degree.     

A new class of asymptotically flat stationary axisymmetric vacuum gravitational fields

We present the full four-dimensional metric for a stationary axisymmetric solution of the vacuum Einstein equations related to the Ernst potential which we obtain by application of anarbitrary number of rank-zero HKX transformations to the general static Weyl solution. The metric function is determined in a completely algebraically way. We perform a suitable Ehlers transformation to ensure asymptotic flatness and give the expression for the total mass of this asymptotically flat solution by analyzing the behavior of the solution on the positive z axis.     

Linearization stability of coupled gravitational and scalar fields in asymptotically flat space-times

Using the methods of Choquet-Bruhat, Fischer and Marsden and using weighted Sobolev spaces developed recently by Christodoulou and Choquet-Bruhat, it is proved that the Einstein field equations coupled with self-gravitating scalar fields are linearization stable in asymptotically flat space-times.     

On the physical interpretation of Wesson's gravitational theory

Wesson has proposed a five-dimensional theory of gravity where the fifth dimension is a parametrization of rest mass. In this paper we investigate the spacetime projection of this theory and point out its scalar-vector-tensor nature. A Brans-Dicke theory with=0 is shown to appear as a special case of Wesson's theory. It is pointed out that the task of constructing a realistic gravitational theory according to the scheme suggested by Wesson meets with serious difficulties.     

The topology of asymptotically locally flat gravitational instantons

In this Letter we demonstrate that the intersection form of the Hausel–Hunsicker–Mazzeo compactification of a four-dimensional ALF gravitational instanton is definite and diagonalizable over the integers if one of the Kähler forms of the hyper-Kähler gravitational instanton metric is exact. This leads to their topological classification.     

Sources of gravitational waves in asymptotically flat Einstein-Maxwell spacetime

In this work, the dynamic of isolated systems in general relativity is described when gravitational radiation and electromagnetic fields are present. In this construction, the asymptotic fields received at null infinity together with the regularized null cone cuts equation, and the center of mass of an asymptotically flat Einstein-Maxwell spacetime are used. A set of equations are derived in the low speed regime, linking their time evolution to the emitted gravitational radiation and to the Maxwell fields received at infinity. These equations should be useful when describing the dynamic of compact sources, such as the final moments of binary coalescence and the evolution of the final black hole. Additionally, we compare our equations with those coming from a similar approach given by Newman, finding some differences in the motion of the center of mass and spin of the gravitational system.     

On asymptotically flat space-times

The allowed asymptotic behavior of the Ricci tensor is determined for asymptotically flat space-times. With the aid of Penrose's conformai technique the asymptotic behavior of the components of the metric tensor, Weyl tensor, and spin coefficients in a suitable frame is calculated for such a space-time. For Einstein-Maxwell space-times these results reduce to those of Exton, Newman, Penrose, Unti, and Kozarzewski.     

New series of asymptotically flat axisymmetric and stationary gravitational solutions

The equations for the pseudopotential of Harrison's Bäcklund transformations with seed solution an asymptotically flat solution of the Ernst equation are solved. A new series of asymptotically flat solutions of the equations of general relativity is obtained from the determinants of matrices, whose elements are known. The first solution of the series is calculated as a ratio of two sums of monomials. This solution has five arbitrary real constants. For a particular choice of the constants it becomes Kerr's solution.     

Con formally flat gravitational fields of an ideal fluid

The necessary and sufficient conditions are obtained for gravitational fields of an ideal fluid to be conformally Euclidean. The possible types of field are considered.     

On the models of gravitational fields

Modelling of the gravitational field is discussed within the framework of Einstein's theory. Modelling is defined as the mapping whereby the geodesic lines (the path of test bodies) go into the family of curves given by the equation of a test body motion in a model. Different possible ways of modelling are singled out — namely, the complete, selective, and approximate-selective ones. The theory is applied to the solar gravitational field.Presented at the International Conference on Gravitation and Relativity, Copenhagen, July 1971. Professor Petrov died in the Summer of 1972. He was one of the members of the International Committee on GRG and founder of the Journal on GRG. We are happy to publish this contribution of his and shall respectfully keep him in our memory. (The Editor.)     

On maximal surfaces in asymptotically flat space-times

Existenc of maximal and almost maximal hypersurfaces in asymptotically flat space-times is established under boundary conditions weaker than those considered previously. We show in particular that every vacuum evolution of asymptotically flat data for the Einstein equations can be foliated by slices maximal outside a spatially compact set and that every (strictly) stationary asymptotically flat space-time can be foliated by maximal hypersurfaces. Amongst other uniqueness results, we show that maximal hypersurfaces can be used to partially fix an asymptotic Poincaré group.Supported in part by the NSF grant PHY 8503072 to Yale University     

Conformally flat gravitational fields produced by an ideal fluid

The problem of finding conformally flat gravitational fields produced by a perfect fluid is solved completely.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No.12, pp.22–25, December, 1980.     

On the theory of inertial gravitational fields

The generalized equations of the inertial gravitational field are derived from variational principles. It is shown that variational properties of inertial gravitational potentials have important peculiarities which cause peculiarities of equations obtained.     

On dynamic properties of gravitational fields

Using a theory for the individualization of points of a Riemannian space and introduction or corresponding comoving reference systems for the gravitational field in classical general relativity expressions are obtained for the field energy density as a four-dimensional scalar and a field energy-momentum tensor of rank 2 (not pseudoscalar and pseudotensor, respectively). The results relate to all types of vacuum Riemannian space in agreement with the classifications of A. Z. Petrov and R. Penrose.     

Null surface quantization and quantum theory of massless fields in asymptotically flat space-time

The quantum theory of massless fields in an asymptotically simple space-time is developed. The Schwinger dynamical principle and the Penrose conformal technique are exploited to derive the commutation relations on proper null surfaces in a curved space-time and on null infinities. The explicit expression for theS matrix in an asymptotically simple space-time is presented. The general expression for a density matrix describing particles created in an external field is also given and its possible applications are discussed briefly.     

On the interpretation of gravitational corrections to gauge couplings

Several recent papers discuss gravitational corrections to gauge couplings that depend quadratically on the energy. In the framework of the background-field approach, these correspond in general to adding to the effective action terms quadratic in the field strength but with higher-order space–time derivatives. We observe that such terms can be removed by appropriate local field redefinitions, and do not contribute to physical scattering-matrix elements. We illustrate this observation in the context of open string theory, where the effective action includes, among other terms, the well-known Born–Infeld form of non-linear electrodynamics. We conclude that the quadratically energy-dependent gravitational corrections are not physical in the sense of contributing to the running of a physically-measurable gauge coupling, or of unifying couplings as in string theory.     

Radial asymptotically periodic solutions of the Kuramoto-Sivashinsky equation

Radial steady solutions of the Kuramoto-Sivashinsky equation are studied. It is shown that there exist solutions that approach at infinity the one-dimensional periodic solutions. Both hyperbolic and elliptic periodic solutions are considered.     

On existence and behaviour of asymptotically flat solutions to the stationary Einstein equations

We show existence and uniqueness of asymptotically flat solutions to the stationary Einstein equations inS=³–B _r , whereB _r is a ball of radiousr>0, when a small enough continuous complex function û on S is given. Regularity and decay estimates imply that these solutions are analytic in the interior ofS and also at infinity, when suitably conformally rescaled.     

Gravitational fields with space-times of Bianchi type IX

Spatially homogeneous space-times of Bianchi type IX are considered. A general scheme for the derivation of exact solutions of Einstein’s equations corresponding to perfect fluid plus pure radiation fields is outlined. Some simple rotating Bianchi type IX cosmological models are presented. The details of these solutions are also discussed. The authors felicitate Prof. D S Kothari on his eightieth birthday and dedicate this paper to him on this occasion.