scholarly journals Static solutions in the Freund – Nambu scalar-tensor theory of gravitation

2021 ◽  
Vol 57 (4) ◽  
pp. 464-469
Author(s):  
Yu. P. Vyblyi ◽  
O. G. Kurguzova
Keyword(s):  
Einstein Equations ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Spherically Symmetric ◽  
Scalar Tensor Theory ◽  
Axially Symmetric ◽  
Field Equations ◽  
Tensor Theory ◽  
Static Solutions ◽  
Theory Of Gravitation

Herein, the system of Einstein equations and the equation of the Freund – Nambu massless scalar field for static spherically symmetric and axially symmetric fields are considered. It is shown that this system of field equations decouples into gravitational and scalar subsystems. In the second post-Newtonian approximation, the solutions for spherically symmetric and slowly rotating sources are obtained. The application of the obtained solutions to astrophysical problems is discussed.

scholarly journals Plane Symmetric Solutions of a Scalar-Tensor Theory of Gravitation

1977 ◽  
Vol 30 (1) ◽  
pp. 109 ◽  
Author(s):  
DRK Reddy
Keyword(s):  
General Relativity ◽  
Empty Space ◽  
Scalar Fields ◽  
Scalar Tensor Theory ◽  
Field Equations ◽  
Plane Symmetric ◽  
Zero Mass ◽  
Tensor Theory ◽  
Special Cases ◽  
Theory Of Gravitation

Plane symmetric solutions of a scalar-tensor theory proposed by Dunn have been obtained. These solutions are observed to be similar to the plane symmetric solutions of the field equations corresponding to zero mass scalar fields obtained by Patel. It is found that the empty space-times of general relativity discussed by Taub and by Bera are obtained as special cases.

scholarly journals Non-Riemannian description of Robinson–Trautman spacetimes in Brans–Dicke theory of gravity

2019 ◽  
Vol 28 (04) ◽  
pp. 1950070
Author(s):  
Muzaffer Adak ◽  
Tekin Dereli ◽  
Yorgo Şenikoğlu
Keyword(s):  
Scalar Field ◽  
Differential Forms ◽  
Scalar Tensor Theory ◽  
Field Equations ◽  
Exterior Differential ◽  
Tensor Theory ◽  
Theory Of Gravitation ◽  
Theory Of Gravity ◽  
Future Reference

The variational field equations of Brans–Dicke scalar-tensor theory of gravitation are given in a non-Riemannian setting in the language of exterior differential forms over four-dimensional spacetimes. A conformally rescaled Robinson–Trautman metric together with the Brans–Dicke scalar field are used to characterize algebraically special Robinson–Trautman spacetimes. All the relevant tensors are worked out in a complex null basis and given explicitly in an appendix for future reference. Some special families of solutions are also given and discussed.

scholarly journals ONCE AGAIN ON THIN-SHELL WORMHOLES IN SCALAR–TENSOR GRAVITY

2009 ◽  
Vol 24 (20) ◽  
pp. 1559-1564 ◽  
Author(s):  
KIRILL A. BRONNIKOV ◽  
ALEXEI A. STAROBINSKY
Keyword(s):  
Thin Shell ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Spherically Symmetric ◽  
Shell Surface ◽  
Symmetric Spacetimes ◽  
Tensor Theory ◽  
Thin Shell Wormholes ◽  
Spherically Symmetric Spacetimes ◽  
Static Spherically Symmetric Spacetimes

It is proved that all thin-shell wormholes built from two identical regions of vacuum static, spherically symmetric spacetimes have a negative shell surface energy density in any scalar–tensor theory of gravity with a non-ghost massless scalar field and a non-ghost graviton.

scholarly journals HIGHER DIMENSIONAL SZEKERES' SPACE–TIME IN BRANS–DICKE SCALAR TENSOR THEORY

2004 ◽  
Vol 13 (06) ◽  
pp. 1073-1083
Author(s):  
ASIT BANERJEE ◽  
UJJAL DEBNATH ◽  
SUBENOY CHAKRABORTY
Keyword(s):  
Turning Point ◽  
Coupling Parameter ◽  
Big Bang ◽  
Space Time ◽  
Scalar Tensor Theory ◽  
Field Equations ◽  
Tensor Theory ◽  
Higher Dimensional ◽  
Theory Of Gravitation ◽  
The Big Bang

The generalized Szekeres family of solution for quasi-spherical space–time of higher dimensions are obtained in the scalar tensor theory of gravitation. Brans–Dicke field equations expressed in Dicke's revised units are exhaustively solved for all the subfamilies of the said family. A particular group of solutions may also be interpreted as due to the presence of the so-called C-field of Hoyle and Narlikar and for a chosen sign of the coupling parameter. The models show either expansion from a big bang type of singularity or a collapse with the turning point at a lower bound. There is one particular case which starts from the big bang, reaches a maximum and collapses with the in course of time to a crunch.

scholarly journals Anisotropic Bulk Viscous String Cosmological Model in a Scalar-Tensor Theory of Gravitation

2013 ◽  
Vol 2013 ◽  
pp. 1-5 ◽  
Author(s):  
D. R. K. Reddy ◽  
Ch. Purnachandra Rao ◽  
T. Vidyasagar ◽  
R. Bhuvana Vijaya
Keyword(s):  
Equations Of State ◽  
Momentum Tensor ◽  
Scalar Tensor Theory ◽  
Field Equations ◽  
Physical Conditions ◽  
Bulk Viscous Fluid ◽  
Tensor Theory ◽  
Highly Nonlinear ◽  
Bulk Viscous ◽  
Theory Of Gravitation

Spatially homogeneous, anisotropic, and tilted Bianchi type-VI0model is investigated in a new scalar-tensor theory of gravitation proposed by Saez and Ballester (1986) when the source for energy momentum tensor is a bulk viscous fluid containing one-dimensional cosmic strings. Exact solution of the highly nonlinear field equations is obtained using the following plausible physical conditions: (i) scalar expansion of the space-time which is proportional to the shear scalar, (ii) the barotropic equations of state for pressure and energy density, and (iii) a special law of variation for Hubble’s parameter proposed by Berman (1983). Some physical and kinematical properties of the model are also discussed.

scholarly journals ENERGY DISTRIBUTION OF THE EINSTEIN–KLEIN–GORDON SYSTEM FOR A STATIC SPHERICALLY SYMMETRIC SPACE–TIME IN (2+1) DIMENSIONS

2006 ◽  
Vol 21 (13n14) ◽  
pp. 2853-2861 ◽  
Author(s):  
I. RADINSCHI ◽  
TH. GRAMMENOS
Keyword(s):  
Exact Solution ◽  
Momentum Density ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Spherically Symmetric ◽  
Field Equations ◽  
Density Distributions ◽  
Klein Gordon ◽  
Energy And Momentum ◽  
Momentum Complex

We use Møller's energy–momentum complex in order to explicitly compute the energy and momentum density distributions for an exact solution of Einstein's field equations with a negative cosmological constant, minimally coupled to a static massless scalar field in a static, spherically symmetric background in (2+1) dimensions.

scholarly journals Casimir effect in an axially symmetric spacetime with unparticles

2019 ◽  
Vol 79 (10) ◽  
Author(s):  
V. B. Bezerra ◽  
C. R. Muniz ◽  
H. S. Vieira
Keyword(s):  
Energy Density ◽  
Characteristic Length ◽  
Casimir Effect ◽  
Casimir Energy ◽  
Einstein Equations ◽  
Kerr Solution ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Parallel Plates ◽  
Axially Symmetric

Abstract We investigate the Casimir effect of the massless scalar field in a cavity formed by ideal parallel plates in the spacetime generated by a rotating axially symmetric distribution of vector or scalar (tensor) unparticles, around which the plates orbit. The presence of the unparticles is incorporated to the background by means of a correction to the Kerr solution of the Einstein equations, in which the characteristic length and the scale dimension associated to the unparticle theory are taken into account. We show that the Casimir energy density depends also on these parameters. The analysis of the “ungravity” limit for the Casimir energy density, in which the characteristic length is very large in comparison to the horizon radius, is made, too. At zero temperature, we show that such a limit implies the instability of the system, since the Casimir energy density becomes an imaginary quantity. The general result is compared to the current terrestrial experiments of the Casimir effect. Thermal corrections also are investigated and the ungravity limit again examined, with the aforementioned instability disappearing at high temperatures.

Expanding and nonexpanding conformal wormholes, in scalar–tensor theory

2015 ◽  
Vol 24 (08) ◽  
pp. 1550064 ◽  
Author(s):  
Melis Ulu Dogru ◽  
İhsan Yilmaz
Keyword(s):  
Casimir Effect ◽  
Lyra Geometry ◽  
Anisotropic Fluid ◽  
Spherically Symmetric ◽  
Scalar Tensor Theory ◽  
Field Equations ◽  
Geometrical Properties ◽  
Big Rip ◽  
Tensor Theory ◽  
Big Crunch

We study spherically symmetric spacetime with anisotropic fluid in the scalar–tensor theory of gravity based on Lyra geometry. We suggest two different solutions of field equations for the theory by using Casimir effect. Obtained static and nonstatic solutions are similar to nonexpanding Lorentzian wormhole and expanding FRW-type wormhole, respectively. Furthermore, we study singularities of obtained solutions. We emphasize whether the expanding and nonexpanding wormholes conform with Big Rip or Big Crunch scenarios. Also, physical and geometrical properties of the solutions have been discussed.

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