共查询到20条相似文献,搜索用时 15 毫秒
1.
Eric A Lord 《Pramana》1975,4(4):164-170
A new generalisation of Einstein’s theory is proposed which is invariant under conformal mappings. Two scalar fields are introduced
in addition to the metric tensor field, so that two special choices of gauge are available for physical interpretation, the
‘Einstein gauge’ and the ‘atomic gauge’. The theory is not unique but contains two adjustable parameters ζ anda. Witha=1 the theory viewed from the atomic gauge is Brans-Dicke theory (ω=−3/2+ζ/4). Any other choice ofa leads to a creation-field theory. In particular the theory given by the choicea=−3 possesses a cosmological solution satisfying Dirac’s ‘large numbers’ hypothesis. 相似文献
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Conformal transformations are frequently used tools in order to study relations between various theories of gravity and Einstein's general relativity theory. In this paper we discuss the rules of these transformations for geometric quantities as well as for the matter energy‐momentum tensor. We show the subtlety of the matter energy‐momentum conservation law which refers to the fact that the conformal transformation “creates” an extra matter term composed of the conformal factor which enters the conservation law. In an extreme case of the flat original spacetime the matter is “created” due to work done by the conformal transformation to bend the spacetime which was originally flat. We discuss how to construct the conformally invariant gravity theories and also find the conformal transformation rules for the curvature invariants R2, RabRab, RabcdRabcd and the Gauss‐Bonnet invariant in a spacetime of an arbitrary dimension. Finally, we present the conformal transformation rules in the fashion of the duality transformations of the superstring theory. In such a case the transitions between conformal frames reduce to a simple change of the sign of a redefined conformal factor. 相似文献
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In order to analyze how the gravitational constant, G, and the cosmological constant, Λ, may vary we study through symmetry principles the form of the functions in the generalized scalar-tensor theories under
the self-similar hypothesis. The results obtained are absolutely general and valid for all the Bianchi models and the flat
FRW one. We study the concrete example of the Kantowski–Sachs model finding some new exact self-similar solutions. 相似文献
6.
G. E. Gorelik 《Russian Physics Journal》1973,16(1):42-45
A transformation is obtained, relating the static, spherically symmetric solutions of Heckman and Brans-Dicke. The size of the singular region is studied as a function of the parameter . It is shown that for > 0 the test particle reaches a singular surface at a finite time.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 56–60, January, 1973.The author is grateful to Professor D. D. Ivanenko for constant attention and fruitful discussions of this work. 相似文献
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We have shown that, within the context of scalar-tensor theories, the anisotropic Bianchi-type cosmological models evolve
towards de Sitter Universe. A similar result holds in the case of cosmology in Lyra manifold. Thus the analogue of cosmic
no-hair theorem of Wald [1] hold in both the cases. In fact, during inflation there is no difference between scalar-tensor
theories, Lyra’s manifold and general relativity (GR). 相似文献
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V. I. Reizlin 《Russian Physics Journal》1981,24(5):401-405
The problem of slow rotation of relativistic bodies in the scalar-tensor theory of gravitation is solved. An equation describing the rotation, its external solution, and the expression for the angular momentum and moment of inertia are obtained in first order with respect to the angular velocity.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 22–26, May, 1981.In conclusion, the author is deeply grateful to V. A. Filimonov for valuable suggestions and remarks. 相似文献
10.
D. K. Ross 《General Relativity and Gravitation》1975,6(2):157-164
The author's geometrical theory of the scalar-tensor gravitational field is extended by formulating it in terms of a Lagrangian. An exact solution of the coupled nonlinear field equations for a static point mass is also presented. This theory which is conformally equivalent to the empty spaceEinstein equations predicts the same results for experiments as the usual theory of Brans and Dicke which has a non-zero energy momentum tensor. 相似文献
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Dierck -Ekkehard Liebscher 《General Relativity and Gravitation》1975,6(3):277-280
The bi-metric theory recently proposed by Rosen is examined in the case of superdense static objects. 相似文献
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Yu. S. Mavrychev 《Russian Physics Journal》1973,16(5):696-697
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Explicit field equations in the general scalar-tensor theory of gravitation proposed by Nordtvedt are obtained with the aid of a static spherically symmetric conformally flat metric. Exact static solutions of Nordtvedt-Barker field equations both in vacuum and in the presence of a source-free electromagnetic field are presented and studied. It is shown that there are no spherically symmetric static conformally flat solutions of Nordtvedt-Barker field equations representing perfect fluid distribution with disordered radiation obeying the equation of state=3p, except for the trivial empty flat space-time of Einstein's theory. 相似文献
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Yousef Bisabr 《General Relativity and Gravitation》2009,41(2):305-313
We study the holographic dark energy model in a generalized scalar tensor theory. In a universe filled with cold dark matter
and dark energy, the effect of potential of the scalar field is investigated in the equation of state parameter. We show that
for a various types of potentials, the equation of state parameter is negative and transition from deceleration to acceleration
expansion of the universe is possible. 相似文献
17.
Nathan Rosen 《General Relativity and Gravitation》1979,10(8):639-646
In the bimetric theory of gravitation with a flat-space background metric conservation laws for energy and momentum are considered in several different forms. In the bimetric theory with a constant-curvature background metric a previous error in the energy-momentum relation is corrected. 相似文献
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