On ghost neutrinos in the Einstein-Cartan theory of gravitation

Different characterization of ghost neutrinos in the Einstein-Cartan theory of gravitation are proposed and analyzed.     

A geometrical property of action in gravitation theory

It is shown that in regard to the special spacial foliation associated with the gas of a standard clock, the action of gravitation theory is proportional to the time parameter, while the coefficient of proportionality is equal to the energy of the gravitational field and other fields in the reference system formed by the gas of the standard clock.St. Petersburg State Technical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 81–84, November, 1993.     

A bi-metric theory of gravitation

A bi-metric theory of gravitation is proposed, satisfying the covariance and equivalence principles. It is based on a simple form of Lagrangian and has a simpler mathematical structure than that of the general theory of relativity. The theory agrees with general relativity up to the accuracy of the observations made up to now. The static spherically symmetric solution of the present field equations does not involve any 'black hole'.     

A scalar field theory of gravitation

A scalar theory of gravitation is developed from a variational principle. The speed of light is taken to be a function of the potential of the gravitational field. The predictions of the light deflection and the advancement of the perihelion agree with those made by Einstein's theory. The gravitational (active) mass differs from the inertial (passive) mass and both are dependent on the gravitational potential.     

Resolving the ghost problem in nonlinear massive gravity

We analyze the ghost issue in the recently proposed models of nonlinear massive gravity in the Arnowitt-Deser-Misner formalism. We show that, in the entire two-parameter family of actions, the Hamiltonian constraint is maintained at the complete nonlinear level and we argue for the existence of a nontrivial secondary constraint. This implies the absence of the pathological Boulware-Deser ghost to all orders. To our knowledge, this is the first demonstration of the existence of a consistent theory of massive gravity at the complete nonlinear level, in four dimensions.     

A background-dependent approach to the theory of gravitation

On the basis of a Machian view of nature we find a covariant formulation of Newton's gravitational equation in a general frame which satisfies the requirements (i) of being singular if the density of mass is zero everywhere and (ii) of depending on the parallel transport of the four-momentum density of matter (from the three-space point in which it is defined to any other three-space point, at any fixed time) in such a way that it incorporates the idea that the frame has to be fixeddirectly in connection with the distribution and motion of matter. In Paper II we will use such an equation as starting point in order to find relativistic gravitational equations which are supposed to hold in any conceivable universe, describe a purely geometrical theory of gravitation, and explicitly incorporate Mach's principle.     

A bi-metric theory of gravitation. II

The bi-metric theory of gravitation proposed previously is simplified in that the auxiliary conditions are discarded, the two metric tensors being tied together only by means of the boundary conditions. Some of the properties of the field of a particle are investigated; there is no black hole, and it appears that no gravitational collapse can take place. Although the proposed theory and general relativity are at present observationally indistinguishable, some differences are pointed out which may some day be susceptible of observation. An alternative bimetric theory is considered which gives for the precession of the perihelion 5/6 of the value given by general relativity; it seems less satisfactory than the present theory from the aesthetic point of view.     

A charge of finite size in the bimetric gravitation theory

The bimetric gravitational field of a charged finite body is derived using a method of approximation. It is found that, with certain exceptions, every charged body has a minimum size, beyond which the field variables become singular. For elementary particles this minimum radius is negligibly small.     

A non-covariant theory of gravitation,I

Homogeneous isotropic models of the universe, based on the general theory of relativity, lead to the existence of a preferred frame of reference, which is similar to the absolute space of, Newton, and a preferred time coordinate, which resembles the absolute time of Newton. These concepts seem to be in contradiction to the principle of covariance on which the general relativity theory is based. A theory of gravitation is therefore proposed which uses the world picture of general relativity but is not covariant. In the three crucial tests, the proposed theory gives the same results as the general relativity theory. However, in contrast to general relativity, the present theory predicts the emission of gravitational waves by spherically symmetric systems, and gravitational waves are found, in general, to have both transverse and longitudinal components.     

A non-covariant theory of gravitation,II

This is a continuation of a previous paper, in which a theory of gravitation was developed based on the existence of a preferred frame of reference and a preferred time coordinate in the universe. The gravitational field equations are derived with the help of a variational principle containing three constants. Two relations among the constants are introduced, leaving one of them arbitrary. This constant does not affect the precession of the perihelion of Mercury but does affect the behaviour of gravitational waves. By changing one of the relations among the constants, one can account for the discrepancy in the precession of the perihelion associated with the oblateness of the sun, as found by Dicke and Goldenberg.     

A coupled theory of electromagnetism and gravitation

A coupling electromagnetism with a previously developed scalar theory of gravitation is presented. The principle features of this coupling are: (1) a slight alteration to the Maxwell equations, (2) the motion of a charged particle satisfies an equation with the Lorentz force-appearing on the right side in place of zero, and (3) the energy density of the electromagnetic field appears in the gravitational field equation in a manner similar to the mass term in the Klein-Gordonequation. The field of a static, spherically symmetric charged particle is computed. The electromagnetic field gives rise to l/r ² terms in the gravitational potential.     

On the Goldstonic gravitation theory

The physical specificity of gravity as a Goldstone-type field responsible for spontaneous breaking of space-time symmetries is investigated and extended up to supergravity. Problems of the Higgs gravitation vacuum and its matter sources are discussed. A particular “dislocation” structure of a space-time due to Poincaré translation gauge fields and the corresponding modification of Newton’s gravitational potential are predicted.     

Cosmology in the Einstein-Cartan theory of gravitation

A number of new solutions to Einstein-Cartan equations for homogeneous isotropic models of the universe are obtained. A catalog of these and earlier found solutions is given, in comparison with typical General Relativity models.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 25–29, March, 1988.The author wants to thank Prof. V. N. Ponomarev for his supervision and help in this work, and I. S. Nurgaliev for the discussion of the results and valuable comments.     

Collapse in the scalar-tensor theory of gravitation

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.     

Lorentz-Covariant theory of gravitation

A Lorentz-covariant theory of gravitation is proposed. It is based on a simple form of the Lagrangian for the gravitational field. The field equations have a simple mathematical structure where the energy-momentum tensor of matter and of gravitational field is the source of the field. The theory agrees with general relativity for the three well-known effects, i.e., red shift, deflection of light, and perihelion.     

Matrix theory of gravitation

A new classical theory of gravitation within the framework of general relativity is presented. It is based on a matrix formulation of four-dimensional Riemann-spaces and uses no artificial fields or adjustable parameters. The geometrical stress-energy tensor is derived from a matrix-trace Lagrangian, which is not equivalent to the curvature scalar R. To enable a direct comparison with the Einstein-theory a tetrad formalism is utilized, which shows similarities to teleparallel gravitation theories, but uses complex tetrads. Matrix theory might solve a 27-year-old, fundamental problem of those theories (Sect. 4.1). For the standard test cases (PPN scheme, Schwarz schild-solution) no differences to the Einstein-theory are found. However, the matrix theory exhibits novel, interesting vacuum solutions.     

Space-time foliations in gravitation theory

A relationship is established between gravitational fields and space-time foliations on a manifold X⁴; the gravitational singularities are described as singularities of these foliations representing critical points of real functions on X⁴.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 20–23, September, 1982.     

On the bimetric theory of gravitation

Rosen's bimetric theory is analyzed anew and is shown to have deficiencies if the space is assumed to be Riemannian. The problems are due mainly to the introduction of the flat metric , and the identification of the stress-energy tensor,T . It is indicated that if the Riemannian interpretation could be avoided the theory still holds promise as a viable theory of gravitation.     

Momentum transfer in gravitation theory

An inductive flux of gravitational momentum in Newtonian theory, and a radiative flux of gravitational momentum in general relativity, while being physically dissimilar quantities, are shown to be formally equivalent by expressing them in terms of a symplectic form on the solution space of the respective field equations. The conditions under which the relativistic flux may be considered inductive are then investigated, and a physical example of how this might occur is given in the setting of a strongly curved space-time.