Solutions Of Brans-Dicke Theory Research Articles

Cosmological solution in Brans-Dicke theory involving particle creation in relativistic viscous fluid universe*

Cosmological solution in Brans-Dicke theory involving particle creation in relativistic viscous fluid universe*

Stationary axially symmetric solutions in Brans-Dicke theory

Stationary, axially symmetric Brans-Dicke-Maxwell solutions are reexamined in the framework of the Brans-Dicke (BD) theory. We see that, employing a particular parametrization of the standard axially symmetric metric simplifies the procedure of obtaining the Ernst equations for axially symmetric electrovacuum space-times for this theory. This analysis also permits us to construct a two parameter extension in both Jordan and Einstein frames of an old solution generating technique frequently used to construct axially symmetric solutions for BD theory from a seed solution of general relativity. As applications of this technique, several known and new solutions are constructed including a general axially symmetric BD-Maxwell solution of Plebanski-Demianski with vanishing cosmological constant, i.e. the Kinnersley solution and general magnetized Kerr-Newman--type solutions. Some physical properties and the circular motion of test particles for a particular subclass of Kinnersley solution, i.e., a Kerr-Newman-NUT--type solution for BD theory, are also investigated in some detail.

On generalized Einstein-Rosen waves in Brans-Dicke theory

In this paper cylindrically symmetric vacuum solutions corresponding to generalized Einstein-Rosen-type gravitational waves are considered in the framework of Brans-Dicke (BD) scalar-tensor theory. We see that, similar to axially symmetric vacuum solutions, under some assumptions, it is possible to generate BD-vacuum solutions from corresponding solutions in general relativity. Using this generating technique, we present several exact solutions corresponding to soliton, standing or pulse waves in BD theory. We also present a Kasner-type time-dependent generalization of cylindrically symmetric static vacuum solution. Some physical implications of these solutions are discussed in some detail. The effect of pulse type waves on test particle motion is briefly discussed and compared with static vacuum background. We also see that, similar to general relativity, there are no trapped cylinders in Einstein-Rosen-type solutions in BD theory.

Lifshitz black holes in Brans-Dicke theory

We present an exact asymptotically Lifshitz black hole solution in Brans-Dicke theory of gravity in arbitrary n(≥ 3) dimensions in presence of a power-law potential. In this solution, the dynamical exponent z is determined in terms of the Brans-Dicke parameter ω and n. Asymptotic Lifshitz condition at infinity requires z > 1, which corresponds to − (n − 1)/(n − 2) ≤ ω < −n/(n − 1). On the other hand, the no-ghost condition for the scalar field in the Einstein frame requires 0 < z ≤ 2(n − 2)/(n − 3). We compute the Hawking temperature of the black hole solution and discuss the problems encountered and the proposals in defining its thermodynamic properties. A generalized solution charged under the Maxwell field is also presented.

Uniqueness of self-similar asymptotically Friedmann-Robertson-Walker spacetime in Brans-Dicke theory

We investigate spherically symmetric self-similar solutions in Brans-Dicke theory. Assuming a perfect fluid with the equation of state $p=(\gamma-1)\mu (1 \le \gamma<2)$, we show that there are no non-trivial solutions which approach asymptotically to the flat Friedmann-Robertson-Walker spacetime if the energy density is positive. This result suggests that primordial black holes in Brans-Dicke theory cannot grow at the same rate as the size of the cosmological particle horizon.

The electrogravity transformation and global monopoles in scalar-tensor gravity

The electrogravity transformation is defined by an interchange of the `active' and `passive' electric parts of the Riemann tensor. Such a transformation has been used to find new solutions that are `dual' to the Kerr family of black hole spacetimes in general relativity. In such a case, the dual solution is a similar black hole spacetime endowed with a global monopole charge. Here, we extend this formalism to obtain solutions dual to the static, spherically symmetric solutions of two different scalar-tensor gravity theories. In particular, we first study the duals of the charged black hole solutions of a four-dimensional low-energy effective action of heterotic string theory. Next, we study dual of the Xanthopoulos-Zannias solution in Brans-Dicke theory, which contains a naked singularity. We show that, analogous to general relativity, in these scalar-tensor gravity theories the dual solutions are similar to the original spacetimes, but with a global monopole charge.

Gravitating monopole and its black hole solution in Brans-Dicke theory

We find a self-gravitating monopole and its black hole solution in Brans-Dicke theory. We mainly discuss the properties of these solutions in the Einstein frame and compare the solutions with those in general relativity.

New black hole solutions in Brans-Dicke theory of gravity

An existence check of nontrivial, stationary axisymmetric black hole solutions in the Brans-Dicke theory of gravity in different directions from those of Penrose, Thorne and Dykla, and Hawking is performed. Namely, working directly with the known explicit spacetime solutions in Brans-Dicke theory, it is found that nontrivial Kerr-Newman-type black hole solutions different from general relativistic solutions could occur for the generic Brans-Dicke parameter values $\ensuremath{-}5/2&lt;~\ensuremath{\omega}&lt;\ensuremath{-}3/2.$ Finally, issues such as whether these new black holes carry scalar hair and can really arise in nature, and if they can, what the associated physical implications would be, are discussed carefully.

Brans-Dicke wormholes in nonvacuum spacetime

Analytical wormhole solutions in Brans-Dicke theory in the presence of matter are presented. It is shown that the wormhole throat must not be necessarily threaded with exotic matter.

Black hole area in Brans-Dicke theory

We have shown that the dynamics of the scalar field $\phi (x)= ``G^{-1}(x)"$ in Brans-Dicke theories of gravity makes the surface area of the black hole horizon {\it oscillatory} during its dynamical evolution. It explicitly explains why the area theorem does not hold in Brans-Dicke theory. However, we show that there exists a certain non-decreasing quantity defined on the event horizon which is proportional to the black hole entropy for the case of stationary solutions in Brans-Dicke theory. Some numerical simulations have been demonstrated for Oppenheimer-Snyder collapse in Brans-Dicke theory.

Approximate black holes for numerical relativity.

Spherically symmetric solutions in Brans-Dicke theory of relativity with zero coupling constant, $\omega=0$, are derived in the Schwarzschild line-element. The solutions are obtained from a cubic transition equation with one small parameter. The exterior space-time of one family of solutions is arbitrarily close to the exterior Schwarzschild space-time. These nontopological solitons have some similarity with soliton stars, and are proposed as candidates for {\em approximate black holes} for the use in numerical relativity, in particular for treatment of horizon boundary conditions.

Wormhole Solution in Vacuum Brans-Dicke Theory with Cosmological Constant

In this paper, we give an Euclidean wormhole solution in the Brans-Dicke theory with cosmological constant. We show that this wormhole is unlike all the others, its configuration is non-static. The throat radius of the wormhole will increase as Euclidan cosmic time increases.

Kerr-type solution in Brans-Dicke theory

The Kerr-type solution in the Brans-Dicke theory should contain three parameters: a massm, a rotational parametera 0, and a coupling parameterω It goes over to the Kerr solution in Einstein's theory of general relativity in the limitω → 8. Using these conditions, we construct a special solution from Bruckman's solutions which can be regarded as a Kerr-type solution in the Brans-Dicke theory.

A class of cosmological solutions of Brans-Dicke theory with cosmological constant

We present a class of exact cosmological solutions of Brans-Dicke (B-D) equations with cosmological constant in flat Robertson-Walker metric. These solutions are based on the relation oRn= constant between the B-D field and the scale factor of the universe. This relation turns out to be consistent with the equation of statep =mρ for the cosmic matter, provided thatn andm are suitably related to each other. Several special cases and asymptotic solutions are derived and discussed.

Exact solutions in Brans-Dicke theory with bulk viscosity

The effect of bulk viscosity on the evolution of the homogeneous and isotropic cosmological models in the Brans-Dicke theory of gravitation is studied. Solutions are found, with a baratropic equation of state, a time-independent bulk viscosity, the gravitational “constant” inversely proportional to the age of the universe, and the mass of the universe (in the closed model) proportional to the square of its age; the expansion factor is a linear function of the cosmological time. For flat space, power law expansions are found, among them one that is related to extended inflation.

Amplification of gravitational waves in scalar-tensor theories of gravity.

The gravitational wave equation for a spatially flat Friedmann-Robertson-Walker universe is derived in the context of scalar-tensor theories of gravity, which have the Brans-Dicke theory as a particular case. This equation is solved for several cosmological scenarios, including the expansions governed by the Nariai as well as the Gurevich-Finkelstein-Ruban solutions of Brans-Dicke theory and for a new set of exact solutions of other scalar-tensor theories. The amplification of gravitational waves is studied in comparison to what happens in the general relativistic case. It is shown how the coupling with the scalar field changes the scales defining very large and very small wave numbers, and consequently the value of the amplification coefficient. It is found that very small values for the coupling parameter could lead to amplification of subhorizon waves. The creation of the corresponding high-frequency gravitons is explained as a response to the rapid time variation of the gravitational "constant," which can occur near the singularity in some models. It is also shown that there could be amplification of waves even in a radiation-dominated universe in some cases, because the wave equation is not conformally invariant, except for the case of Nariai's solution in the Brans-Dicke theory.

The isotropization of the vacuum Bianchi type ? V solution

In a recent paper, the general vacuum Bianchi type-V solution in Brans-Dicke theory was presented and the isotropization of the model was discussed. It is pointed out that this solution was derived previously. Some remarks are made about the isotropization of the model.

Inflationary solutions in general scalar tensor theory of gravitation

Extended inflation solution in Brans-Dicke theory given by Mathiazhagan and Johri (MJ) is shown as the unique solution only if the scale factor is assumed to be a power function of the scalar field. Only the consistent solution amongst the set of solutions given by Patra, Roy and Ray is found identical to the MJ solution. Both exponential inflation and power function inflation are studied in general scalar tensor theory where the parameter to is a function of the scalar, field. It is noted that exponential inflation is forbidden in Brans-Dicke theory wherew is a constant.

A comment on the Brans-Dicke cosmology for a radiation universe

The cosmological solutions of Brans-Dicke theory for a radiation universe obtained so far are commented on. Some problematic solutions are corrected and the conditions corresponding to singularity-free solutions are investigated.

Exact solutions in brans-dicke theory: A dynamical system approach

A method is furnished for constructing isotropic and homogeneous solutions in Brans-Dicke theory based on the analysis of the dynamical system formed by the field equations. Large classes of solutions found in the literature are recovered and shown to be special cases of those generated by this method.