Showing papers on "Four-force published in 1987"
TL;DR: In this paper, it was shown that an analog of Birkhoff's theorem of general relativity exists in the scale-covariant theory of gravitation when the gauge function which occurs in the theory is independent of time.
Abstract: It is shown that an analog of Birkhoff's theorem of general relativity exists in the scale-covariant theory of gravitation when the gauge function which occurs in the theory is independent of time.
45 citations
TL;DR: The geometric optics approximation in general relativity is critically examined in this paper, where the well-known result that rays of radiation follow null geodesics of the gravitational field is shown to be valid only in the limit of vanishing wavelength.
40 citations
TL;DR: The possibility of a nonstandard definition of simultaneity is implicitly contained in a general covariant formulation of the special theory of relativity, and it is shown that conditions such as the one they derived are satisfied automatically as mentioned in this paper.
Abstract: In a recent article, De Ritis and Guccioni claimed to give an easy way of falsifying the conventionalist interpretation of the definition of simultaneity of distant events within an inertial system. For a particular closed light path, they derived a necessary condition and claimed that it could be violated by a nonstandard choice of the definition of simultaneity. It is pointed out here that (as shown by many authors) the possibility of a nonstandard definition is implicitly contained in a generally covariant formulation of the special theory of relativity, and it is shown that conditions such as the one they derived are satisfied automatically. The most general position-independent definition of simultaneity is given, and an example of a position- as well as direction-dependent definition is exhibited in an Appendix. A number of objections against the possibility of a nonstandard definition of simultaneity raised by various authors are discussed and are found to lack any physical or mathematical justification.
37 citations
32 citations
TL;DR: In this article, it was shown that space-times admitting more than one independent Killing-Yano tensor belong to a small collection of highly idealised space times, and a new characterization of Robertson-Walker space times arises as a corollary of the main theorem.
Abstract: It is shown that space-times admitting more than one independent Killing-Yano tensor belong to a small collection of highly idealised space-times. A new characterization of Robertson-Walker space-times arises as a corollary of the main theorem.
28 citations
01 Jan 1987
25 citations
TL;DR: The structure of the Poisson-brackets algebra of constraints of general relativity is reexamined using the recently introduced spinorial variables to provide a point of departure for a nonperturbative quantization scheme for general relativity.
Abstract: The structure of the Poisson-brackets algebra of constraints of general relativity is reexamined using the recently introduced spinorial variables. Three different combinations of constraints are analyzed and their relative merits are discussed. In each case we construct the corresponding expression of the Becchi-Rouet-Stora-Tyutin charge. These expressions provide a point of departure for a nonperturbative quantization scheme for general relativity.
22 citations
TL;DR: As one of my colleagues put it, “Asking about the impact of special relativity on theoretical physics is like asking about Shakespeare on the English language as discussed by the authors. An impossibly large, even senseless, task.
Abstract: As one of my colleagues put it, “Asking about the impact of special relativity on theoretical physics is like asking about the impact of Shakespeare on the English language.” An impossibly large, even senseless, task. Special relativity is a fact of life, part and parcel of the way nature is. If its impact on everyday life is slight, its impact on physicists' thinking is profound. Space and universal, inexorable time were rudely united into space‐time by Albert Einstein's discovery of special relativity. Explorations of the properties of space‐time, of the covariance of physical laws, and of the physical invariants of nature, together with quantum mechanics, led to the formulation of relativistic quantum field theories. The external symmetries of space‐time were augmented by abstract spaces for internal symmetries corresponding to invariant (conserved) quantities such as isospin, strangeness and charm. The whole worldview of modern theoretical physics can be traced back to the fundamental postulate or idea that physical phenomena do not change just because you happen to be moving by, instead of standing still, when observing them. Rotations and other transformations in internal spaces have replaced “moving by,” but the idea is the same.
17 citations
TL;DR: The main idea is to include the spin as a thermodynamic variable in the theory to derive the equations of motion for a spinning fluid in the Einstein-Cartan theory.
Abstract: Methods used earlier to derive the equations of motion for a spinning fluid in the Einstein-Cartan theory are specialized to the case of general relativity. The main idea is to include the spin as a thermodynamic variable in the theory.
17 citations
15 citations
TL;DR: In this paper, an exact solution of the field equations of general relativity is obtained for a static, spherically symmetric distribution of charge and mass, which includes as special cases the results given previously by Cooperstock and De La Cruz, Mehra and Bohra, Santos, and Shi-Chang.
Abstract: An exact solution of the field equations of general relativity is obtained for a static, spherically symmetric distribution of charge and mass. Their physical properties are studied in some detail. Our solution includes as special cases the results given previously by Cooperstock and De La Cruz, Mehra and Bohra, Santos, and Shi-Chang.
TL;DR: In this article, a commonsense approach to Special Relativity based on direct observation instead of from the usual rationale conceived in terms of light travelling invisibly in vacuo is presented. This approach permits the construction of a model of the time dilation effect.
Abstract: We present a new commonsense approach to Special Relativity based on direct observation instead of from the usual rationale conceived in terms of light travelling invisibly in vacuo. This approach permits the construction of a model of the time dilation effect.
01 Sep 1987
TL;DR: In this paper, the Lagrangian formulation of compact binary systems is considered in post-Newtonian approximations of general relativity, and the results concerning the equations of motion and associated Lagrangians are reported.
Abstract: We consider the two-body problem in post-Newtonian approximations of general relativity. We report the recent results concerning the equations of motion, and the associated Lagrangian formulation, of compact binary systems, at the third post-Newtonian order (∼ 1/c beyond the Newtonian acceleration). These equations are necessary when constructing the theoretical templates for searching and analyzing the gravitational-wave signals from inspiralling compact binaries in VIRGO-type experiments. c © 2001 Académie des sciences/Éditions scientifiques et médicales Elsevier SAS general relativity/equations of motion Sur le problème des deux corps en relativité générale Résumé. Nous considérons le problème des deux corps dans l’approximation post-newtonienne de la relativité générale. Nous présentons les résultats récents concernant les équations du mouvement, et la formulation lagrangienne associée, de systèmes binaires d’objets compacts, au troisième ordre post-newtonien (∼ 1/c après l’accélération newtonienne). Ces équations sont utilisées dans la construction des filtres théoriques pour la détection et l’analyse des signaux d’ondes gravitationnelles provenant des binaires compactes spiralantes dans les expériences du type VIRGO. c © 2001 Académie des sciences/Éditions scientifiques et médicales Elsevier SAS relativité générale/équations du mouvement Note présentée par First name NAME S1296-2147(01)01171-?/FLA c © 2001 Académie des sciences/Éditions scientifiques et médicales Elsevier SAS. Tous droits réservés. 1
TL;DR: In this article, an analogy between the light barrier and a black hole event horizon in the theory of relativity is drawn, and it is shown that bradyon-tachyon-antibradyon transformations are possible in the proper reference frame by a constant acceleration.
Abstract: The extended space-time manifold in a uniformly accelerating reference frame is considered both for positive and negative accelerations. An analogy between the light barrier and a black hole event horizon in the theory of relativity is drawn. It is shown that bradyon-tachyon-antibradyon transformations are possible in the proper reference frame by a constant acceleration, i.e. for the light barrier penetration.
TL;DR: In this article, the self-creation theory of gravitation is solved for the Robertson-Walker space-time, by using a correspondence to known solutions of general relativity, by solving the vacuum field equations of the self creation theory.
Abstract: The vacuum field equations of the self-creation theory of gravitation are solved for the Robertson-Walker space-time, by using a correspondence to known solutions of general relativity.
TL;DR: In this article, it was shown that the proofs of a series of classical singularity theorems of general relativity can be modified such that these theorem also state the maximality of the incomplete nonspacelike geodesics.
Abstract: It is shown that the proofs of a series of classical singularity theorems of general relativity can be modified such that these theorems also state the maximality of the incomplete nonspacelike geodesics. Since along maximal incomplete nonspacelike geodesics with affine parameter u certain parts of the tidal curvature cannot blow up faster than (u−u)−2, where u is the parameter value until which the geodesics cannot be extended, the classical singularity theorems do restrict the behavior of the curvature.
02 Jun 1987
TL;DR: The history and current status of computer algebra programs for this field are reviewed, their applications are described in outline, and the “equivalence problem” is discussed as a more detailed example.
Abstract: After a brief introduction to the theory of relativity, the history and current status of computer algebra programs for this field are reviewed (though full system descriptions are not given). Their applications are described in outline, and the “equivalence problem” is discussed as a more detailed example. Recent developments are highlighted. Finally some prospects and problems are mentioned.
TL;DR: The uniqueness of the Friedmann-Robertson-Walker (FRW) cosmological models was established in this paper. But the uniqueness of FRW cosmologies was not discussed in this paper.
Abstract: By accepting the validity of certain conjectures in classical general relativity and kinetic theory, it is argued that, in a sense, the spatially homogeneous and isotropic Friedmann-Robertson-Walker (FRW) cosmological models are unique. This is accomplished in two steps. First, there is reason to believe that kinetic theory requires perfect fluids to be shear-free. Second, it seems that general relativity constrains expanding shear-free fluids to be irrotational. The uniqueness of the FRW models then follows, since it has already been established that they are the only space-times which represent an expanding shear-free irrotational perfect fluid that are physically reasonable on a global scale.
TL;DR: In this paper, the invalidity of the general theory of relativity as a physical theory of gravitation and the construction of a relativistic theory of gravity possessing all attributes of field theories were discussed.
Abstract: Two questions are discussed: (1) the invalidity of the general theory of relativity as a physical theory of gravitation and (2) the construction of a relativistic theory of gravitation possessing all attributes of field theories.
TL;DR: In this article, the main features of the solution generating techniques are outlined, the generalization to Einstein-Maxwell fields is discussed and some applications are given, as well as some applications.
Abstract: Stationary axisymmetric gravitational fields are governed by the Ernst equation. Its internalSU(1, 1) symmetry gives rise to a linear problem and to Backlund transformations which map known solutions into new ones. The main features of the solution generating techniques are outlined, the generalization to Einstein-Maxwell fields is discussed and some applications are given.
TL;DR: The theory of gravity chain this article consists of general relativity, nonmetric theories of gravity, Newton's theory of gravitation, and the special theory of relativity, all of which describe the relations between the abstract objects of partial models subordinated to the basic one.
Abstract: The analysis of theory‐choice problems in modern theory of gravity necessitates consideration of the genesis and structure of the systems of gravitational abstract objects. My approach to physical theory structure uses and develops the ideas of V. S. Stepin. The fundamental equations of general relativity Einstein's equations ‐ are shown to describe the relations between the abstract objects of the basic model only. The theory of gravity chain consists of general relativity, nonmetric theories of gravitation, Newton's theory of gravitation and the special theory of relativity. All these theories describe the relations between the abstract objects of partial models subordinated to the basic one.
TL;DR: The Hermitian theory of relativity is regarded as the theory of a field endowed with two sources: electromagnetic and color four-currents as discussed by the authors, and the equilibrium conditions for charges and currents are apparent in exact solutions of the field equations.
Abstract: The equilibrium conditions for charges and currents, apparent in exact solutions of the field equations, lead one to regard the Hermitian theory of relativity as the theory of a field endowed with two sources: electromagnetic and color four-currents.
TL;DR: In this paper, a generalization of general relativity to non-abelian geometries is proposed, where the diffeomorphisms of GRS may be regarded as transformations that preserve the abelian group structure of the translation operators.
TL;DR: In this article, the solutions obtained by Kramer (1984) for a rotating perfect fluid in general relativity are generalised and a few results are noted that seem mathematically interesting and may be applicable elsewhere.
Abstract: Solutions obtained by Kramer (1984) for a rotating perfect fluid in general relativity are generalised. In the process a few results are noted that seem mathematically interesting and may be applicable elsewhere.
TL;DR: In this article, it was shown that a singularity will exist even in cases where geodesic focusing does not occur for some geodesics, even when the conditions that are generally imposed are fairly weak and can be expected to hold for most geodesians in any reasonable space-time.
Abstract: A key ingredient of the singularity theorems of general relativity is that geodesics will focus under certain conditions. While the conditions that are generally imposed are fairly weak and can be expected to hold for most geodesics in any reasonable space‐time, the question arises of what the consequences might be if these conditions happen to fail to hold for isolated geodesics. The standard singularity theorems in the literature do not cover such cases. A result is presented here that demonstrates that a singularity will exist even in cases where geodesic focusing does not occur for some geodesics.
01 May 1987
TL;DR: In this paper, it is shown that whereas the predictions of the relativistic theory of gravitation for gravitational effects are unambiguous and agree with the known experimental data, the corresponding predictions of general theory of relativity are ambiguous.
Abstract: It is shown that whereas the predictions of the relativistic theory of gravitation for gravitational effects are unambiguous and agree with the known experimental data, the corresponding predictions of the general theory of relativity are ambiguous. In some effects, the ambiguity appears in the first order in the gravitational coupling constant; in others, in the second. The absence in the general theory of relativity of conservation laws for energy, momentum, and angular momentum of the matter and gravitational field taken together, and also its inability to give unique predictions for gravitational phenomena, make it necessary to abandon the theory of relativity as a physical theory.
TL;DR: Using the canonical Hamiltonian for vierbein general relativity, the ten primary constraints are shown to lead to four secondary constraints, and the algebra of these constraints is found and is consistent with the constraint algebras previously known as mentioned in this paper.
Abstract: Using the canonical Hamiltonian for vierbein general relativity, the ten primary constraints are shown to lead to four secondary constraints. The algebra of these constraints is found and is consistent with the constraint algebras previously known.