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1.
The present Letter represents an exact, static, and spherically-symmetric solution of Einstein's field equations for a homogeneous perfect fluid core surrounded by a field of Zeldovich's fluid which is asymptotically homaloidal.  相似文献   

2.
The study of Einstein field equations describing the Robertson-Walker universe with the Brans-Dicke field and perfect fluid has been made. It is found that the exact solutions to the B-D field interacting with perfect fluid reduce to a false vaccum with cosmological constant and without cosmological constant the solution reduce to the exact solution of the matter dust distribution in the Brans-Dicke cosmology. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

3.
We present a conformally-flat metric in general relativity representing the gravitational field of a spherically-symmetric material distribution-radiating energy in the form of photons and neutrinos. A particular case of the solution is discussed and the corresponding expressions for mass function, linear dimension, and the luminosity have been derived. The solution seems to be physically sound as it corresponds to positive expressions for fluid pressure, fluid density, and radiation flux density.  相似文献   

4.
The unsteady free-convection flow of an electrically-conducting fluid near a moving vertical plate of infinite extent is investigated in the presence of uniform transverse magnetic field fixed to the fluid or to the plate. Exact solution of this problem is obtained with the aid of the Laplace transform technique, when the plate is moving with a velocity which is an arbitrary functiuon of time. The solution is exemplified for three particular cases of physical interest; the non-magnetic case is also discussed.  相似文献   

5.
An algorithm is derived for constructing spatially-homogeneous perfect fluid solutions of Einstein's field equations which are of Bianchi type-I and are locally rotationally-symmetric. Starting from Bayin and Krisch solution a new exact solution is obtained. Some physical and kinematic properties of the cosmological model are discussed.  相似文献   

6.
A new solution of Einstein-Maxwell field equations is presented. The material content of the field described by this solution is a perfect fluid plus sourceless electromagnetic fields. The metric of the solution is explicitly written. This metric is examined as a possible representation of Kerr-Newman metric embedded in Einstein static universe. The Kerr-Newman metric in the background of Robertson-Walker universe is also briefly described.  相似文献   

7.
The unsteady flow of an electrically conducting fluid past an infinite plate with constant suction is investigated in the presence of an external magnetic field and buoyancy forces. The temperature of the plate is assumed to oscillate in time about a constant mean and the flow is considered to be free of convection. For the method of solution, we have employed a small parameter approach when this small parameter is a non-dimensional quantity which is related to the viscoelastic constant of the fluid. Analytical expressions are obtained for the temperature distribution and the velocity profile of the fluid. These analytical results clearly show that the velocity profile is strongly damped when the magnetic field is more intense. This means that the applied magnetic field causes the fluid to move slower as compared with the non-magnetic case.  相似文献   

8.
Relativistic cosmological field equations are obtained for a non-static stationary Bertotti-Robinson-type space-time for interacting perfect fluid and electromagnetic field. The cosmological solution to the field equations are obtained and the nature of the electromagnetic field as well the perfect fluid are studied. The electromagnetic field generated here corresponds to a special generic case and the perfect fluid distribution degenerates into a barotropic perfect fluid with equation of statep+=0, >0. It is shown here that the interacting barotropic fluid can generate gravitation only when the cosmological constant being a function ofx in a dynamic field.  相似文献   

9.
This paper is devoted to the study of static axially symmetric spacetime with anisotropic fluid by means of structure scalars in the presence of electromagnetic field. The structure scalars in terms of physical variables are evaluated through the Einstein-Maxwell field equations and the inhomogeneity factors are identified. We also explore analytic solutions for isotropic as well as anisotropic fluids. It is found that isotropic solution turns out to be a charged solution which has no correspondence with the Weyl metrics while the anisotropic solution has the correspondence with the Weyl metrics.  相似文献   

10.
The classical Rayleigh problem has been extended to the case of the hydromagnetic free-convective flow of an electrically-conducting and incompressible viscous fluid past an infinite vertical naturally permeable wall in a rotating system. The applied transverse magnetic field is fixed with the moving wall and the magnetic Reynolds number of the flow is taken small so that the induced magnetic field can be neglected in comparison to the applied magnetic field. The permeable wall starts moving from rest in the still fluid and thus arises an initial value problem whose solution has been obtained by the Laplace transform method for two important cases impulsive as well as accelerated start of the plate. Mathematical expression for skin friction components have been also obtained in a closed form. Asymptotic behaviour of the solution is analysed for both the cases, and some interesting particular cases have also been encountered. Influence of various physical parameters occurring into the problem has been discussed with the aid of graphs and tables.  相似文献   

11.
The anisotropic nature of the dark energy for Bianchi type-VI0 space time is discussed. The exact solution of the Einstein field equations under the assumption on the anisotropy of the fluid are obtained for exponential and power-law volumetric expansions. The isotropy of the fluid, space and expansion are examined.  相似文献   

12.
The Einstein field equations for an irrotational perfect fluid with pressurep, equal to energy density are studied when the space-time is conformally flat. The coordinate transformation to co-moving coordinates is discussed. The energy and Hawking-Penrose inequalities are studied. Static and non-static solutions of the field equations are obtained. It is interesting to note that in the static case the only spherically-symmetric conformally flat solution for self-gravitating fluid is simply the empty flat space-time of general relativity.  相似文献   

13.
Inspired by the analogy between the magnetic field and velocity field of incompressible fluid flow, we propose a fluid dynamics approach for computing nonlinear force-free magnetic fields. This method has the advantage that the divergence-free condition is automatically satisfied, which is a sticky issue for many other algorithms, and we can take advantage of modern high resolution algorithms to process the force-free magnetic field. Several tests have been made based on the well-known analytic solution proposed by Low & Lou. The numerical results are in satisfactory agreement with the analytic ones. It is suggested that the newly proposed method is promising in extrapolating the active region or the whole sun magnetic fields in the solar atmosphere based on the observed vector magnetic field on the photosphere.  相似文献   

14.
Bianchi Type I magnetized Cosmological model for perfect fluid distribution is investigated. The magnetic field is due to an electric current produced along x-axis. The distribution consists of an electrically neutral perfect fluid with an infinite electrical conductivity. To get a determinate solution, a supplementary conditionA = BC between metric potentials is used. The behaviour of the model in presence and absence of magnetic field is also discussed. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

15.
An exact solution of the coupled Einstein-Maxwell equations representing the gravitational field in the interior of a sphere of charged incoherent matter in equilibrium is obtained which is a charged analogue of the static perfect fluid sphere solution with spheroidal 3-space obtained by Vaidya & Tikekar.  相似文献   

16.
In this paper, the nonsteady flow of non-Newtonian power-law conducting fluid through a porous medium past an infinite porous plate is investigated. The system is stressed by a constant transverse magnetic field. The velocity outside the boundary layer depends exponentially on time. The rheological effects are shown and discussed on the shear stress in terms of rheological parameter of power-law fluid. The approximate solution in a closed form were obtained by using the Galerkin method. Also the effect of the magnetic field and permeability parameter are discussed.  相似文献   

17.
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   

18.
The effect of a transverse magnetic field and of the viscosity diffusion on the free-convection flow of an electrically-conducting incompressible fluid past a uniformally accelerated vertical plate is discussed. A finite difference method has been used to obtain a numerical solution. The influence of the various parameters on the flow field is discussed.  相似文献   

19.
A new class of exact solutions of Einstein's field equations with perfect fluid for an LRS Bianchi type-I spacetime is obtained by using a time dependent deceleration parameter. We have obtained a general solution of the field equations from which three models of the universe are derived: exponential, polynomial and sinusoidal form respectively. The behaviour of these models of the universe are also discussed in the frame of reference of recent supernovae Ia observations.  相似文献   

20.
The three-dimensional flow of an electrically conducting and incompressible viscous fluid past a uniformly accelerated infinite vertical porous plate is studied in a rotating fluid. The flow is assumed to be at small magnetic Reynolds number so that the induced magnetic field is neglected. An exact solution has been obtained by defining a complex velocity with the help of the Laplace transform method for the Prandtl number equal to unity. The effects of rotation, magnetic and free-convection parameters are discussed for the whole problem. Also, the skin-friction components on the plate are discussed.  相似文献   

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