Stability of superdense stars in the bimetric theory of gravitation

Calculations of superdense star models in the Rosen bimetric theory of gravitation are presented. There is a family of quark stars whose members are probably stable even if their masses do not exceed the maximum mass of neutron stars.     

The gravitation theory in bimetric formulation

The gravitation theory is considered in bimetric formulation with a Lagrangian of the most common type and quadratic with respect to the derivativesg _ik/l of the metric tensor. Restrictions on the dimensionless parameters of the theory are found, basing on the comparison with the Newtonian theory and the analysis of corresponding observational data in the vicinity of the solar system. Propagation of the weak gravitation waves is investigated in the outside gravitational field.     

Scalar-tensor bimetric theory of gravitation. I

Institute of Applied Physics Problems, Armenian Academy of Sciences. Translated from Astrofizika, Vol. 32, No. 3, pp. 491–500, May–June, 1990.     

Non-existence of cosmic strings in bimetric theory of gravitation

Bianchi type cosmological models are considered in Bimetric theory of gravitation proposed by Rosen (1973) in the context of cosmic strings. It is interesting to note that cosmic strings do not occur in Bianchi type cosmologies. This revised version was published online in July 2006 with corrections to the Cover Date.     

Stationary axial-symmetric fields in the rosen bimetric theory of gravitation

In the quadratic approximation to the angular velocity of rotation, general solutions of the Rosen bimetric theory of gravitation are found which define the structure of the external, stationary axial-symmetric gravitational field.     

Models of neutron stars in generalized bimetric theory of gravitation

Yerevan State University; Institute of Applied Physics Problems, Armenian Academy of Sciences. Translated fromAstrofizika, Vol. 35, No. 1, pp. 121–129, July–August, 1991.     

String cosmological models in five dimensional bimetric theory of gravitation

Five-dimensional spherically symmetric space-time is considered in bimetric theory of gravitation formulated by Rosen (Gen. Rel. Grav. 4, 435, 1973) in the presence of cosmic string dust cloud. Exact cosmological models which represent geometric (Nambu) string, p-string (Takabayasi string) and Reddy string (Astrophys. Space Sci. 301, 2006) are obtained in the static and non-static cases. Some physical properties of the models are also discussed.     

The bimetric theory of gravitation with a dynamic background metric

We study the bimetric theory of gravitation with background metric _ik. In contrast to the accepted point of view, in which _ik, is a metric given a priori, we assume that _ik is a dynamic variable determined from the condition that the total action of the gravitating system must be an extremum. As a result it turns out that (1) _ik can be described by the Einstein equation in space-time with the metric _ik and (2) the energy-momentum tensor of the graviational field _ik, is the source of _ik. In this sense _ik can be considered a secondary field in relation to g_ik. We determine the conditions for existence of integral covariant conservation laws. Two of the latter have no analogs in the theory with the background metric given a priori.Translated fromAstrofizika, Vol. 37, No. 3, 1994.The author is grateful to the participants in the seminar of the Department of Theoretical Physics at Erevan State University, and also to W. Bleier, K. A. Bronnikov, V. N. Mel'nikov, and G. Yu. Treder for discussions and valuable remarks. The investigations presented in this paper were partly financed by the International Scientific Fund, grant Ph1-262-0902.     

Non-existence of higher dimensional anisotropic cosmological model in bimetric theory of gravitation

A Five dimensional spherically symmetric space-time model in Rosen's (1973) bimetric theory of gravitation is considered. It is shown that, in this theory, the geometry of the five dimensional space-time does not admit perfect fluid source. Hence a vacuum model is presented and studied. It is observed that in the case of stiff fluid we again get the vacuum model. This revised version was published online in July 2006 with corrections to the Cover Date.     

On birkhoff’s theorem in the bimetric scalar-tensor theory of gravitation

It is shown that in the most general version of the bimetric scalar-tensor theory of gravitation, a spherically symmetric vacuum gravitational field is static if the gravitational scalar does not depend on time. This result is generalized to certain cases in which a source is present, including an electromagnetic field. Both branches of solutions with a variable and a constant scalar field are considered. Translated from Astrofizika, Vol. 40, No. 2, pp. 281–290, April–June, 1997.     

On the election of the flat metric in the bimetric theory of gravitation

The problem of the form of the flat metric in the Rosen bimetric theory is examined in the following work.It is shown, on concrete examples, how necessary it is to write down the flat metric and solve the problem of finding the gravitational field in arbitrary non-inertial frame. It is shown also how to separate the pure gravitational effects from those connected with non-inertiality of the frame by way of comparing both metrics.