GENERALIZED SCALAR–TENSOR THEORY FOR BIANCHI SPACETIME MODELS

2004 ◽  
Vol 19 (09) ◽  
pp. 703-711
Author(s):  
NARAYAN CHANDRA CHAKRABORTY ◽  
SUBENOY CHAKRABORTY
Keyword(s):  
Scalar Field ◽  
Viscous Fluid ◽  
Einstein Equations ◽  
Physical Parameters ◽  
Scalar Tensor Theory ◽  
Coupling Constant ◽  
Bulk Viscous Fluid ◽  
Tensor Theory ◽  
Bulk Viscous ◽  
Variable Coupling

This work deals with Bianchi cosmological models where geometry is coupled to a scalar field with variable coupling constant (depending on the scalar field). Considering a bulk viscous fluid, the possibility of exponential or power law form of solutions have been examined. The modified Einstein equations have been solved with some reasonable assumptions among the physical parameters and solutions have been discussed.

COSMOLOGICAL MODELS IN GENERALIZED SCALAR–TENSOR THEORY WITH CAUSAL VISCOUS FLUID

1998 ◽  
Vol 07 (06) ◽  
pp. 849-856
Author(s):  
G. P. SINGH ◽  
S. G. GHOSH ◽  
AROONKUMAR BEESHAM
Keyword(s):  
Scalar Field ◽  
Viscous Fluid ◽  
Nonequilibrium Thermodynamics ◽  
Coupling Parameter ◽  
Scalar Tensor Theory ◽  
Bulk Viscous Fluid ◽  
Tensor Theory ◽  
Bulk Viscous ◽  
Friedmann Robertson Walker ◽  
Causal Thermodynamics

We consider generalized Brans–Dicke theory in which the coupling parameter is not constant but a function of the scalar field. Friedmann–Robertson–Walker models with bulk viscous fluid source described by full (i.e., nontruncated) causal nonequilibrium thermodynamics are analyzed. Exact solutions for the flat case have been obtained. Our results are compared with those in the usual Brans–Dicke theory with causal thermodynamics.

Isotropic Cosmological Model in Generalized Scalar Tensor Theory with Bulk Viscosity

1997 ◽  
Vol 06 (01) ◽  
pp. 119-124 ◽  
Author(s):  
N. Banerjee ◽  
Aroonkumar Beesham
Keyword(s):  
Scalar Field ◽  
Cosmological Model ◽  
Viscous Fluid ◽  
Bulk Viscosity ◽  
Conformal Transformation ◽  
Scalar Tensor Theory ◽  
Bulk Viscous Fluid ◽  
Tensor Theory ◽  
Bulk Viscous ◽  
Isotropic Cosmological Model

In this paper both exponential and power law solutions for the flat Robertson–Walker cosmological model have been derived in a generalized Brans–Dicke theory, where the parameter ω is a function of the scalar field, along with a bulk viscous fluid. The solutions are obtained in Dicke's revised units and these are also given in the original atomic units via the conformal transformation prescribed by Dicke.

GENERALIZED SCALAR TENSOR THEORY IN FOUR AND HIGHER DIMENSION

2000 ◽  
Vol 09 (05) ◽  
pp. 543-549 ◽  
Author(s):  
SUBENOY CHAKRABORTY ◽  
ARABINDA GHOSH
Keyword(s):  
Physical Parameters ◽  
Scalar Tensor Theory ◽  
Higher Dimension ◽  
Field Equations ◽  
Bianchi I ◽  
Bulk Viscous Fluid ◽  
Tensor Theory ◽  
Bulk Viscous ◽  
Coupled Field ◽  
Coupled Field Equations

In this paper, we have considered generalized scalar–tensor theory for four-dimensional Bianchi-I model and also for a five-dimensional cosmological model. We have studied both exponential and power law solutions, considering a bulk viscous fluid. To solve the complicated coupled field equations, we have made assumptions among the physical parameters and solutions have been discussed.

scholarly journals Brans - Dicke Cosmology with Causal Viscous Fluid

1996 ◽  
Vol 49 (5) ◽  
pp. 899 ◽  
Author(s):  
N Banerjee ◽  
A Beesham
Keyword(s):  
Scalar Field ◽  
Cosmological Model ◽  
Viscous Fluid ◽  
Exact Solutions ◽  
Power Function ◽  
Causal Theory ◽  
Scale Factor ◽  
Scalar Tensor Theory ◽  
Equilibrium Thermodynamics ◽  
Tensor Theory

Exact solutions for the spatially flat (k = 0) Robertson–Walker cosmological model in Brans–Dicke scalar tensor theory have been obtained in the presence of a causal viscous fluid. It is found that if the scale factor is a power function of the scalar field, then solutions can be obtained in the full causal theory but not in the truncated theory of non-equilibrium thermodynamics.

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.

GALACTIC AND ASTROPHYSICAL SIZES FROM SCALAR-TENSOR THEORY OF GRAVITY

2004 ◽  
Vol 13 (02) ◽  
pp. 359-371 ◽  
Author(s):  
GIUSEPPE BASINI ◽  
MARCO RICCI ◽  
FULVIO BONGIORNO ◽  
SALVATORE CAPOZZIELLO
Keyword(s):  
Scalar Field ◽  
Spiral Galaxies ◽  
Weak Field ◽  
Newtonian Potential ◽  
Scalar Tensor Theory ◽  
Field Limit ◽  
Weak Field Limit ◽  
Tensor Theory ◽  
Flat Rotation Curves ◽  
Theory Of Gravity

We investigate the weak-field limit of scalar-tensor theory of gravity and show that results are directly depending on the coupling and self-interaction potential of the scalar field. In particular, corrections are derived for the Newtonian potential. We discuss astrophysical applications of the results, in particular the flat rotation curves of spiral galaxies.

Brans–Dicke type teleparallel scalar–tensor theory

2017 ◽  
Vol 32 (34) ◽  
pp. 1750183 ◽  
Author(s):  
Mustafa Salti ◽  
Oktay Aydogdu ◽  
Hilmi Yanar ◽  
Figen Binbay
Keyword(s):  
General Relativity ◽  
Dark Energy ◽  
Scalar Field ◽  
Noether Symmetry ◽  
Scalar Tensor Theory ◽  
Minimal Coupling ◽  
Energy Effect ◽  
New Model ◽  
Symmetry Approach ◽  
Tensor Theory

The teleparallel alternative of general relativity which is based on torsion instead of curvature is considered as the gravitational sector to explore the dark universe. Inspired from the well-known Brans–Dicke gravity, here, we introduce a new proposal for the galactic dark energy effect. The new model includes a scalar field with self-interacting potential and a non-minimal coupling between the gravity and scalar field. Additionally, we analyze the idea via the Noether symmetry approach and thermodynamics.

scholarly journals PLANE-SYMMETRIC INHOMOGENEOUS BULK VISCOUS COSMOLOGICAL MODELS WITH VARIABLE Λ

2003 ◽  
Vol 12 (05) ◽  
pp. 941-951 ◽  
Author(s):  
ANIRUDH PRADHAN ◽  
HARE RAM PANDEY
Keyword(s):  
Cosmological Model ◽  
Viscous Fluid ◽  
Cosmological Constant ◽  
Ad Hoc ◽  
Fluid Distribution ◽  
Geometric Features ◽  
Plane Symmetric ◽  
Bulk Viscous Fluid ◽  
Variable Λ ◽  
Bulk Viscous

A plane-symmetric non-static cosmological model representing a bulk viscous fluid distribution has been obtained which is inhomogeneous and anisotropic and a particular case of which is gravitationally radiative. Without assuming any ad hoc law, we obtain a cosmological constant as a decreasing function of time. The physical and geometric features of the models are also discussed.

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