共查询到20条相似文献，搜索用时 947 毫秒
1.
The problem of slowly rotating cosmological viscous fluid universe in a homogeneous and isotropic models has been investigated by considering the perturbation in the metric rotation function to the first order of smallness associated with certain physical restrictions imposed on the metric rotation function and matter angular velocity. Some more general solutions for the metric rotation function have been obtained and physical interpretation of the solutions have been investigated. 相似文献
2.
The study of Einstein's field equations describing Robertson-Walker cosmological models with massive scalar field and viscous fluid representing the matter has been made. The problem has been investigated with and without the source density in the wave equation. Corresponding exact solutions of the field equations have been obtained under different physical equations of state: namely, (i) dust distribution, (ii) Zeldovich fluid distribution, (iii) disordered distribution of radiation subject to physically realistic conditions. The physical interpretations of the physically realistic solutions has been investigated. It has been found that physically realistic solutions has been obtained for closed cosmological models only. 相似文献
3.
A procedure to generate new exact solutions to Einstein equations for perfect fluids is applied to LRS Bianchi type I line-element. Starting from some known solutions a class of new perfect fluid solutions of Bianchi type I are presented. The physical and kinematical properties of spatially homogeneous and anisotropic cosmological models are studied. 相似文献
4.
In this work, some numerical solutions of magnetohydrodynamic equations are investigated in the presence of radial and azimuthal components of magnetic field with the use of previously developed algorithm. In this algorithm, the thin shell approximation and a special separation of variables is used to obtain the radial and latitudinal variations of physical parameters in spherical coordinates. The solutions are obtained via this separation of variables in the components of momentum transfer equation. The analysis yields three important parameters which are the sphericity, density and radial components shape parameters in the latitudinal distributions of physical variables. The magnetic field profile, used here, produces comparable magnetic fluxes found in previous works. There is a considerable change in density with respect to reference model. Other physical parameters also reveal important physical results. It is as well shown that the spherical symmetric distributions of physical parameters are broken for the region of study. 相似文献
5.
Static and spherical symmetric solutions of the field equations in the bimetric general theory of gravitation are obtained
for perfect and anisotropic charged fluids under the assumption that the physical metric admits a one-parameter group of conformal
motion. All solutions are matched to the Reissner–Nordstrom metric and possess positive energy density larger than the stresses,
everywhere within the sphere. The solution agrees with Einstein’s general relativity for a physical system comparable to the
size of the universe, such as the solar system. 相似文献
6.
We investigate a class of solutions of Einstein equations for the plane symmetric perfect fluid case. If these solutions have
shear, they must necessarily be non-static. Some physical and geometric properties of the models are also discussed.
相似文献
7.
Exact nonstatic solutions to Einstein field equations are obtained for the plane symmetric spacetime filled with viscous perfect fluid in the presence of attractive scalar fields. Some physical and geometrical properties of the model are studied. The solutions characterize strong interaction of elementary particles. 相似文献
8.
N. Ibotombi Singh S. Surendra Singh S. Romaleima Devi 《Astrophysics and Space Science》2010,326(2):293-297
Field equations of cosmological models with bulk viscosity are constructed in the scale covariant theory of gravitation. A
new class of solutions for the model is found by applying a variable deceleration parameter. Some physical implications of
these solutions are briefly discussed. 相似文献
9.
《天文和天体物理学研究(英文版)》2015,(10)
We revisit the problem of the maximum masses of magnetized white dwarfs(WDs).The impact of a strong magnetic field on the structure equations is addressed.The pressures become anisotropic due to the presence of the magnetic field and split into parallel and perpendicular components.We first construct stable solutions of the Tolman-Oppenheimer-Volkoff equations for parallel pressures and find that physical solutions vanish for the perpendicular pressure when B(?) 10~(13) G.This fact establishes an upper bound for a magnetic field and the stability of the configurations in the(quasi) spherical approximation.Our findings also indicate that it is not possible to obtain stable magnetized WDs with super-Chandrasekhar masses because the values of the magnetic field needed for them are higher than this bound.To proceed into the anisotropic regime,we can apply results for structure equations appropriate for a cylindrical metric with anisotropic pressures that were derived in our previous work.From the solutions of the structure equations in cylindrical symmetry we have confirmed the same bound for B ~ 10~(13) G,since beyond this value no physical solutions are possible.Our tentative conclusion is that massive WDs with masses well beyond the Chandrasekhar limit do not constitute stable solutions and should not exist. 相似文献
10.
Friedmann Robertson Walker cosmological models with bulk viscosity are constructed in the scale covariant theory of gravitation.
A new class of solutions for the field equations of the model is found by applying variable deceleration parameter. Some physical
models of these solutions are briefly discussed in this paper. 相似文献
11.
J. K. Singh 《Astrophysics and Space Science》2008,317(1-2):39-44
A class of new exact solutions of the Einstein field equations have been investigated for stationary cylindrically symmetric space-time around a local cosmic string in the theory based on Lyra’s geometry in normal gauge in the presence and absence of an electromagnetic field. The cosmological solutions have been analyzed through various physical and geometrical parameters. It has also been shown that the solutions are space-time inhomogeneous and filled with charged dust. 相似文献
12.
We present analytic solutions of the Einstein-Maxwell equations for cosmological models of LRS Bianchi type-II, VIII, and IX. The solutions represent anisotropic universes with source-free electromagnetic fields and perfect fluids matter satisfying the equation of state that is a function of the cosmic-time. Some physical properties of the models have been discussed. 相似文献
13.
The solutions of Einstein’s equations with cosmological constant (Λ) in the presence of a creation field have been obtained for general class of anisotropic cosmological models. We have obtained the cosmological solutions for two different scenarios of average scale factor. In first case, we have discussed three different types of physically viable cosmological solutions of average scale factor for the general class of Bianchi cosmological models by using a special law for deceleration parameter which is linear in time with a negative slope. In second case, we have discussed another three different forms of cosmological solutions by using the average scale factor in three different scenarios like Intermediate scenario, Logamediate scenario and Emergent scenario. All physical parameters are calculated and discussed in each physical viable cosmological model. We examine the nature of creation field and cosmological constant is dominated the early Universe but they do not survive for long time and finally tends to zero for large cosmic time t. We have also discussed the all energy conditions in each cases. 相似文献
14.
We perform a detailed physical analysis for a class of exact solutions for the Einstein–Maxwell equations. The linear equation of state consistent with quark stars has been incorporated in the model. The physical analysis of the exact solutions is performed by considering the charged anisotropic stars for the particular nonsingular exact model obtained by Maharaj, Sunzu and Ray. In performing such an analysis we regain masses obtained by previous researchers for isotropic and anisotropic matter. It is also indicated that other masses and radii may be generated which are in acceptable ranges consistent with observed values of stellar objects. A study of the mass-radius relation indicates the effect of the electromagnetic field and anisotropy on the mass of the relativistic star. 相似文献
15.
This paper deals with the general class of Bianchi cosmological models with bulk viscosity and particle creation described by full causal thermodynamics in Brans-Dicke theory. We discuss three types of average scale-factor solutions for the general class of Bianchi cosmological models by using a special law for the deceler- ation parameter which is linear in time with a negative slope. The exact solutions to the corresponding field equations are obtained in quadrature form and solutions to the Einstein field equations are obtained for three different physically viable cosmologies. All the physical parameters are calculated and discussed in each model. 相似文献
16.
The principal objections to our paper on Jordan-Brans-Dicke Bianchi-type universes are misleading. The intended solutions assume a power-law form, only in the limit of very large times. Although this is the only one for which we wrote down explicit solutions. The physical point of view behind our paper was to extend the re-scaling method, developed by one of us, to anisotropic universes in general and not to make a detailed study of each of the possible solutions that could be obtained through this process. 相似文献
17.
In this paper we have obtained interior solutions of the field equations for anisotropic sphere in the bimetric general relativity theory formulated by Rosen (Lett. Nuovo Cimento 25, 1979). A class of solutions for a uniform energy-density source of the field equations is presented. The analytic solutions obtained are physically reasonable, well behaved in the interior of the sphere. The solutions agree with the Einstein’s general relativity for a physical system compared to the size of the universe such as the solar system. 相似文献
18.
Ioannis Gkigkitzis Ioannis Haranas Samantha Kirk 《Astrophysics and Space Science》2013,346(2):553-557
In this study, we have investigated the geometrical and physical properties of stationary axisymmetric solutions. The expressions for the axial-vector and the gravitational energy and momentum densities are obtained in the context of teleparallel equivalent of general relativity. The obtained results are compared with that obtained previously in the context of Møller’s tetrad theory of gravitation. We discussed special cases of these solutions. 相似文献
19.
Field equations are obtained with the aid of higher dimensional Bianchi type-I cosmological model in scale covariant theory
of gravitation in the context of cosmic strings. We present here isotropic and anisotropic solutions of the field equations
and some physical implications of these solutions are briefly discussed. 相似文献
20.
A technique to generate new exact Bianchi type-III cosmological solutions of massive strings in the presence of magnetic field is presented. Starting from Tikekar and Patel's strings models in the absence and presence of the magnetic field, new solutions are obtained. Some of their physical features are discussed. 相似文献