scholarly journals ENERGY–MOMENTUM IN VISCOUS KASNER-TYPE UNIVERSE IN BERGMANN–THOMSON FORMULATIONS

2005 ◽  
Vol 20 (10) ◽  
pp. 2169-2177 ◽  
Author(s):  
MUSTAFA SALTI ◽  
ALI HAVARE
Keyword(s):  
Total Energy ◽  
Space Time ◽  
Cosmological Models ◽  
Energy And Momentum ◽  
Momentum Complex ◽  
The Universe ◽  
Friedmann Robertson Walker

Using the Bergmann–Thomson energy–momentum complex and its tele-parallel gravity version, we obtain the energy and momentum of the universe in viscous Kasner-type cosmological models. The energy and momentum components (due to matter plus field) are found to be zero and this agree with a previous work of Rosen and Johri et al. who investigated the problem of the energy in Friedmann–Robertson–Walker universe. The result that the total energy and momentum components of the universe in these models is zero supports the viewpoint of Tryon. Rosen found that the energy of the Friedmann–Robertson–Walker space–time is zero, which agrees with the studies of Tryon.

scholarly journals DIFFERENT APPROACHES FOR MØLLER'S ENERGY IN THE KASNER-TYPE SPACETIME

2005 ◽  
Vol 20 (28) ◽  
pp. 2175-2182 ◽  
Author(s):  
MUSTAFA SALTI
Keyword(s):  
General Relativity ◽  
Gravitational Field ◽  
Energy Distribution ◽  
Total Energy ◽  
Theory Of Gravity ◽  
Energy And Momentum ◽  
The Universe ◽  
Friedmann Robertson Walker

Considering the Møller energy definition in both Einstein's theory of general relativity and tele-parallel theory of gravity, we find the energy of the universe based on viscous Kasner-type metrics. The energy distribution which includes both the matter and gravitational field is found to be zero in both of these different gravitation theories and this result agrees with previous works of Cooperstock and Israelit et al., Banerjee–Sen, Vargas who investigated the problem of the energy in Friedmann–Robertson–Walker universe in Einstein's theory of general relativity and Aydogdu–Saltı who considered the same problem in tele-parallel gravity. In all of these works, they found that the energy of the Friedmann–Robertson–Walker spacetime is zero. Our result is the same as that obtained in the studies of Saltı and Havare. They used the viscous Kasner-type metric and found the total energy and momentum by using Bergmann–Thomson energy–momentum formulation in both general relativity and tele-parallel gravity. The result that the total energy and momentum components of the universe is zero supports the viewpoints of Albrow and Tryon.

Further Results of Flat Space-time Theory of Gravitation

2005 ◽  
Vol 60 (4) ◽  
pp. 255-264
Author(s):  
Walter Petry
Keyword(s):  
Solar System ◽  
Flat Space ◽  
High Energy ◽  
Space Time ◽  
Cosmological Models ◽  
Compact Objects ◽  
Anomalous Acceleration ◽  
Theory Of Gravitation ◽  
The Universe ◽  
Time Theory

Abstract The anomalous acceleration of spacecrafts in the solar system is explained. An explanation of the observed superluminal velocities of jets at extragalactic objects is given. The extension of quasars can be larger as generally assumed, i. e. quasars must not be very compact objects. An explanation of the high energy loss per unit time of quasars is given. The relation between the velocity of an object in the universe and its redshift is stated. All these results are received from cosmological models studied by flat space-time theory of gravitation and the post-Newtonian approximation of perfect fluid in these cosmological models where clocks at earlier times are going faster than at present.

scholarly journals COSMOLOGICAL MODELS GENERALIZING ROBERTSON–WALKER MODELS

2003 ◽  
Vol 12 (09) ◽  
pp. 1603-1613
Author(s):  
ABDUSSATTAR
Keyword(s):  
Space Time ◽  
Cosmological Models ◽  
Einstein’S Field Equations ◽  
Field Equations ◽  
Einstein's Field Equations ◽  
The Universe

Considering the physical 3-space t= constant of the space–time metrics as spheroidal and pseudo-spheroidal, cosmological models which are generalizations of Robertson–Walker models are obtained. Specific forms of these general models as solutions of Einstein's field equations are also discussed in the radiation and the matter dominated era of the universe.

scholarly journals Axially Symmetric Bulk Viscous String Cosmological Models in GR and Brans-Dicke Theory of Gravitation

2013 ◽  
Vol 2013 ◽  
pp. 1-5 ◽  
Author(s):  
V. U. M. Rao ◽  
D. Neelima
Keyword(s):  
General Relativity ◽  
Bulk Viscosity ◽  
Space Time ◽  
Cosmological Models ◽  
Axially Symmetric ◽  
Matter Distribution ◽  
Field Equations ◽  
Theory Of Gravitation ◽  
The Universe ◽  
Special Case

Axially symmetric string cosmological models with bulk viscosity in Brans-Dicke (1961) and general relativity (GR) have been studied. The field equations have been solved by using the anisotropy feature of the universe in the axially symmetric space-time. Some important features of the models, thus obtained, have been discussed. We noticed that the presence of scalar field does not affect the geometry of the space-time but changes the matter distribution, and as a special case, it is always possible to obtain axially symmetric string cosmological model with bulk viscosity in general relativity.

Cosmological models for an homogeneous, isotropic universe

2018 ◽  
Author(s):  
Michael Kachelriess
Keyword(s):  
Time Evolution ◽  
Space Time ◽  
Scale Factor ◽  
Cosmological Models ◽  
Isotropic Universe ◽  
Friedmann Equations ◽  
Homogeneous Isotropic Universe ◽  
The Universe

The universe is homogeneous and isotropic on sufficiently large scales. The metric which describes such a space-time is derived and it is shown that it is determined by the scale factor a(t) and the parameter k distinguishing between hyperbolic, flat, or spherical 3-spaces. The Friedmann equations, which describe the time evolution of these models, are derived and specific models are discussed.

scholarly journals DARK ENERGY IN SOME INTEGRABLE AND NONINTEGRABLE FRW COSMOLOGICAL MODELS

2011 ◽  
Vol 20 (12) ◽  
pp. 2419-2446 ◽  
Author(s):  
KURALAY ESMAKHANOVA ◽  
NURGISSA MYRZAKULOV ◽  
GULGASYL NUGMANOVA ◽  
YERLAN MYRZAKULOV ◽  
LEONID CHECHIN ◽  
...  
Keyword(s):  
Dark Energy ◽  
Cosmological Models ◽  
Gravity Models ◽  
New Class ◽  
Energy Models ◽  
Acceleration Of The Universe ◽  
Frw Models ◽  
The Universe ◽  
Friedmann Robertson Walker ◽  
Hypergeometric Equations

One of the greatest challenges in today's cosmology to determine the nature of dark energy, the sourse of the observed present acceleration of the universe. Besides the vacuum energy, various dark energy models have been suggested. The Friedmann–Robertson–Walker (FRW) spacetime plays an important role in modern cosmology. In particular, the most popular models of dark energy work in the FRW spacetime. In this work, a new class of integrable FRW cosmological models is presented. These models induced by the well-known Painlevé equations. Some nonintegrable FRW models are also considered. These last models are constructed with the help of Pinney, Schrödinger and hypergeometric equations. Scalar field description and two-dimensional generalizations of some cosmological models are presented. Finally some integrable and nonintegrable F(R) and F(G) gravity models are constructed.

2-COMPONENT INTEGRABLE COSMOLOGICAL MODELS

2005 ◽  
Vol 20 (11) ◽  
pp. 2246-2255 ◽  
Author(s):  
V. N. MELNIKOV ◽  
V. R. GAVRILOV
Keyword(s):  
Scalar Field ◽  
Large Class ◽  
Perfect Fluid ◽  
Space Time ◽  
Cosmological Models ◽  
Perfect Fluids ◽  
Dimensional Models ◽  
Friedmann Robertson Walker

A large class of integrable cosmological models with two matter components is presented. The D-dimensional models on the space-time manifold [Formula: see text] are studied in the presence of 2 separately conserved barotropic perfect fluids. Such model are reducible to pseudo-Euclidean Toda-like system and integrable when their barotropic parameters satisfy some algebraic relations. Methods for integrating of pseudo-Euclidean Toda-like systems are based on the Minkowski-like geometry for characteristic vectors composed from the barotropic parameters. We also apply the methods for the spatially flat Friedmann-Robertson-Walker universe containing a perfect fluid and a minimally coupled self-interacting scalar field with a potential comprised of two exponentials.

COSMOLOGICAL MODELS OF GLOBAL UNIVERSE EVOLUTION AND DECOMPOSITION OF PERTURBATIONS

2002 ◽  
Vol 17 (29) ◽  
pp. 4451-4456 ◽  
Author(s):  
SERGEI V. CHERVON
Keyword(s):  
Sigma Model ◽  
Cosmological Models ◽  
Linear Sigma Model ◽  
Cosmological Perturbations ◽  
Frw Universe ◽  
Global Evolution ◽  
Two Component ◽  
The Universe ◽  
Universe Evolution ◽  
Friedmann Robertson Walker

It is shown that cosmological models, based on the self-interacting scalar field theory or on the theory of the chiral non-linear sigma model. Can describe the global evolution of the Universe, extending from an inflationary stage to the present time epoch. The method of cosmological perturbations decomposition for inflaton and non-inflaton ones is applied for two-component chiral cosmological model in the spatially flat Friedmann-Robertson-Walker (FRW) Universe. New non-inflaton mode of cosmological perturbations is found.

Transit cosmological models in FRW universe under the two-fluid scenario

2019 ◽  
Vol 16 (01) ◽  
pp. 1950007 ◽  
Author(s):  
Pryanka Garg ◽  
Rashid Zia ◽  
Anirudh Pradhan
Keyword(s):  
Cosmological Models ◽  
Observational Cosmology ◽  
Accelerating Universe ◽  
Frw Universe ◽  
Two Fluids ◽  
Slowing Down ◽  
Two Fluid Scenario ◽  
The Universe ◽  
Two Fluid ◽  
Friedmann Robertson Walker

This paper is an attempt to revisit the Friedmann–Robertson–Walker (FRW) cosmological models under the new scenario of observational cosmology, which has established that the current universe is expanding with an increasing rate, in contrast to the earlier belief that the rate of expansion is constant or slowing down. This paper represents a model which encompasses both, earlier decelerating and the current accelerating universe, passing through a transition phase. The universe is assumed to be filled with two fluids, barotropic and dark energy. We have considered two cases; first, when these fluids are assumed to be non-interacting and second, when they interact with each other. Some physical, kinematic and geometric properties of the model are also discussed along with the acceptability and stability of the solution. The results found are very compatible with the established results as well as recent observations.

scholarly journals Simultaneous emergence of curved space–time and quantum mechanics

2016 ◽  
Vol 94 (2) ◽  
pp. 192-200
Author(s):  
S.S. De ◽  
F. Rahaman
Keyword(s):  
Quantum Mechanics ◽  
Field Equation ◽  
Riemannian Space ◽  
Generalized Uncertainty Principle ◽  
Space Time ◽  
Curved Space ◽  
The Universe ◽  
Finslerian Space ◽  
Zero Time ◽  
Friedmann Robertson Walker

It is shown in this paper that the geometrically structureless space–time manifold is converted instantaneously to a curved, a Riemannian, or may be a Finslerian space–time with an associated Riemannian space–time, on the appearance of quantum Weyl spinors dependent only on time in a background flat manifold and having the symplectic property in the abstract space of spinors. The scenario depicts simultaneous emergence of gravity in accord with general relativity and quantum mechanics. The emergent gravity leads to the generalized uncertainty principle, which in turn ushers in discrete space–time. The emerged space–time is specified here as to be Finslerian and the field equation in that space–time has been obtained from the classical one due to the arising quantized space and time. From this field equation we find the quantum field equation for highly massive (of the Planck order) spinors in the associated Riemannian space of the Finsler space, which is in fact, the background homogeneous and isotropic Friedmann–Robertson–Walker space–time of the universe. These highly massive spinors provide the mass distribution complying with the Einstein equivalence principle. All these occurred in the indivisible minimum time considered as zero time or spontaneity.

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