共查询到20条相似文献，搜索用时 578 毫秒
1.
A study of imperfect fluid interacting with the gravitational field for spherically-symmetric Robertson-Walker metric has been carried out. Exact solutions of the field equations of viscous fluid have been obtained under different equations of state. The corresponding physical interpretations of the solutions have been investigated. It has been shown that the occurrence of Big-Bang does not take place when the viscous fluid as only source term interacts with the gravitational field at the initial stages. 相似文献
2.
The paper considers inhomogeneous space-times admitting a two-parameter group of motions and satisfying Einstein's field equations for viscous fluid and perfect fluid with heat conduction. Some homogenous solutions representing viscous fluid have also been obtained for which the free-gravitational field is of the magnetic type. Various physical and kinematical properties have been discussed. 相似文献
3.
The problem of electromagnetic field interacting with viscous fluid without and with zero-mass scalar field has been studied. It has been shown that electromagnetic field cannot interact with viscous fluid for spherically-symmetric Robertson-Walker metric. Exact solutions corresponding to the problem of electromagnetic field interactions in presence of viscous fluid and zero-mass scalar field have been obtained subject to various physical conditions. It presents a scope for the study of imperfect fluid FRW models showing the existence of the electromagnetic field due to the presence of zero-mass scalar field. 相似文献
4.
Exact solutions are obtained for an isotropic homogeneous universe with a bulk viscous fluid in the cosmological theory based on Lyra’s geometry. The viscosity coefficient of the bulk viscous fluid is assumed to be a power function of the mass density. Cosmological models with time dependent displacement field have been discussed for a constant value of the deceleration parameter. Finally some possibilities of further problems and their investigations have been pointed out. 相似文献
5.
Bulk viscous cosmological models of universe with variable deceleration parameter in Lyra’s Manifold
N. Ibotombi Singh S. Romaleima Devi S. Surendra Singh A. Sumati Devi 《Astrophysics and Space Science》2009,321(3-4):233-239
FRW models of universe in the presence of viscous fluid are investigated in the cosmological theory based on Lyra’s Manifold. By considering the deceleration parameter to be a variable and the viscosity coefficient of bulk viscous fluid to be a constant, exacts solutions have been obtained from which three forms of model of the universe are derived. The physical properties of the models are also investigated. 相似文献
6.
The problem of cosmological axially-symmetric viscous fluid interacting with the gravitational field has been investigated.
Exact solution have been obtained for the pressure and density of the fluid. Physical interpretation of the solutions regarding
the expansion factor, acceleration components and reality condition have been made.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
7.
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
8.
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
9.
Steady plane flows of an incompressible rotating viscous fluid with infinite electrical conductivity are studied. Certain results of physical importance have been deduced for orthogonal flows. Lastly, the solutions to vortex and source flow problems are obtained. 相似文献
10.
Hypersurface–homogeneous cosmological models containing a bulk viscous fluid with time varying G and Λ have been presented. We have shown that the field equations are solvable for any arbitrary cosmic scale function. The
viscosity coefficient of bulk viscous fluid is assumed to be a power function of the energy density. Exact solutions of Einstein’s
field equations are obtained which represent an expanding, shearing and accelerating/decelerating models of the universe.
The physical and kinematical behaviours of the models are also discussed. 相似文献
11.
The occurrence of oscillatory mode for magnetized fluid in the presence of vertical and horizontal temperature gradients has been studied. In both the cases (highly viscous and low-viscosity fluids) the occurrence of oscillatory solutions to the Bénard problem has been investigated as a function of Prandtl number, magnetic number, resistivity number and the ratio of applied temperature gradients. It is clear that the high Prandtl numbers completely change the character of instability and of the solutions as compared to those appropriate for low Prandtl-number fluids. It has also been shown that small horizontal temperature gradient readily generate oscillatory modes only for real frequencies. The critical Rayleigh number is higher than the critical Rayleigh number of non-magnetized fluid in both the cases-i.e., highly viscous fluid and one of moderate viscosity. 相似文献
12.
The effect of finite conductivity on the Rayleigh-Taylor instability of an incompressible, viscous rotating fluid through a porous medium has been studied in the presence of a two-dimensional horizontal magnetic field. It has been shown that the solution is characterized by a variational principle. By making use of the existence of the variational principle, proper solutions have been obtained for a semi-infinite fluid in which density has a one-dimensional (exponential) vertical stratification. The dispersion relation has been derived and solved numerically. It is found that finite resistivity and porosity have a destabilizing effect on the Rayleigh-Taylor instability while rotation has a stabilizing effect. 相似文献
13.
Relativistic cosmological field equations are obtained for a Robertson-Walker space time interacting with viscous fluid and
massive scalar field. The cosmological solutions to the field equations are obtained and the nature of the scalar field as
well as the viscous fluid are studied. It is found that the solutions obtained are realistic only for a closed Universe.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
14.
R. Chaubey 《Astrophysics and Space Science》2012,342(2):499-509
The Bianchi type-V cosmological model with viscous fluid and creation particle in Brans-Dicke theory has been considered. The present paper deals with Bianchi type-V cosmological model with bulk viscosity and particle creation described by full causal thermodynamics in Brans-Dicke theory. We have discussed two types of solutions of the average scale factor for a Bianchi type-V model by using a variation law of Hubble’s parameter, which yields a constant value of the deceleration parameter. The exact solutions to the corresponding field equations are obtained in quadrature form. The solutions to the Einstein field equations are obtained for power law and exponential form. The cosmological parameters have been discussed in detail. 相似文献
15.
A. K. Singh 《Astrophysics and Space Science》1983,93(1):177-184
Hall effects on the MHD flow of an incompressible, electrically-conducting viscous fluid past an impulsively started infinite vertical porous plate has been analysed for the case of small magnetic Reynolds number. Exact solutions have been obtained for the axial and the transverse components of the velocity and the skin-friction by defining a complex velocity with the help of the Laplace transform technique. The velocity profiles are shown graphically and the numerical values of axial and transverse components of skin-friction are tabulated for different values of the dimensionless parameters occurring into the problem. 相似文献
16.
The problem of viscous fluid distribution in Bianchi type I space-time is considered here in a new scalar tensor theory of
gravitation proposed by Saez and Ballester (1986). Particular solutions of the field equations are derived assuming the viscous
coefficient to be the power functions of energy density. Some physical and geometrical properties of the solutions are also
discussed.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
17.
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
18.
A study of the slowly rotating cosmological universe filled with viscous fluid has been made by assuming the matter angular
velocity Ω is proportional to the metric angular velocity Ω and the Universe is expanding under the Hubble's law. The physical
properties of the solutions obtained are also discussed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
19.
An exact cosmological solution for Friedman Robertson Walker (FRW)metric is obtained with a classical scalar field φ along
with a potential in the presence of a causal viscous fluid. Assuming the scale factor to be a function of the scalar field
we have obtained solutions in both the truncated and the full causal theory. It is shown that an inflationary model can be
obtained by imposing certain constraints on some constants. The radiative bulk viscosity during the decoupling era has also
been studied as a special case.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
20.
Exact solutions are obtained in a five-dimensional space-time with an energy-momentum tensor containing a viscous fluid, assuming either an equation of state or a special form for the viscous term in line with the assumption of Belinskii and Khalatnikov (1977). The solutions are, in fact, generalizations of an earlier work by Grøn for a perfect fluid in the 5D rest-mass varying theory of gravity proposed recently by Wesson. It is found that dimensional reduction of the extra space takes place in some of the cases such that the 5-dimensional universe naturally evolves into an effective 4-dimensional one. A huge amount of entropy can be produced following this shrinkage of extra-dimension which may account for the very large value of entropy per baryon observed in our 4D world. Moreover, the observed constancy of the rest-mass in the present era is also interpreted. 相似文献