共查询到20条相似文献，搜索用时 31 毫秒
1.
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
2.
Static spherically symmetric anisotropic source has been studied for the Einstein-Maxwell field equations assuming the erstwhile cosmological constant Λ to be a space-variable scalar, viz., Λ=Λ(r). Two cases are examined out of which one reduces to isotropic sphere. The solutions thus obtained are shown to be electromagnetic in origin as a particular case. It is also shown that the generally used pure charge condition, viz., ρ+p=0 is not always required for constructing electromagnetic mass models. 相似文献
3.
Dieter Lorenz-Petzold 《Astrophysics and Space Science》1983,96(2):343-349
We study the Einstein-Maxwell equations for a tilted Bianchi type-II space-time. The matter content is a perfect fluid, with equation of statep=(γ?1)ε, (1≤γ≤2). The field equations are solved for all values of γ in the limiting case of small vorticity. The source of rotation is an electromagnetic field, which from observational requirements must be a small quantity at the present time. 相似文献
4.
Ramesh Tikekar 《Journal of Astrophysics and Astronomy》1984,5(3):273-276
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
5.
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
6.
The integration of the Einstein-Maxwell equations for an anisotropic charged fluid sphere acting as a source of the Reissner-Nordström metric is considered, under the assumption of a conformally flat interior metric. The solutions asymptotically tend to static configurations. In the isotropic pressure limiting case, the non-static solutions are found to be incompatible with charged models. 相似文献
7.
The Einstein-Maxwell field equations for charged dust corresponding to static axially-symmetric metric of Levi-Civita have been studied. It has been shown that when the metric potentialsg
ij are functions of only one of the coordinates, viz.,r, the interior charged dust becomes purely of electromagnetic origin, in the sense that the physical quantities like the energy density, the effective gravitational mass, etc., are dependent only on the charge density and vanish when this charge density vanishes. Such models are known as electromagnetic mass models in the classical electrodynamics. An interior charged dust solution corresponding to this case has been obtained which, in a sense, represents an infinite dust distribution of electromagnetic origin. In the second case, viz., when the metric potentials are functions of the coordinatesr andz both, it has been shown that some of the situations correspond to electromagnetic mass models. An example to illustrate this case has been obtained. This represents the source of the Reissner-Nordström-Curzon field (an analogue of the Reissner-Nordström solution obtained by Curzon) which according to Curzon describes the exterior field of an electron. 相似文献
8.
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
9.
Saibal Ray 《Astrophysics and Space Science》2002,280(4):345-355
Static spherically symmetric charged dust models, known as Lane-Emden electromagnetic mass models, having their seed in the
well-known Lane-Emden equations of classical astrophysics, have been derived for Einstein-Cartan theory. The models are of
purely electromagnetic origin. The physical significance of these solutions can be understood from the very fact (i) that
they are generated from the well-known Lane-Emden equations of classical astrophysics having a proven physical foundation
and (ii) that, being the solution of Einstein-Cartan theory, they involve spin and torsion, characteristics which a material
system must possess for its subtle and finer details. PACS number(s): 04.90.+e, 04.20.jb.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
10.
D. Lorenz 《Astrophysics and Space Science》1982,85(1-2):63-67
The Einstein-Maxwell equations are integrated for a tilted Bianchi type VIo space-time with stiff matter and an electromagnetic field. The solution represents an anisotropic homogeneous cosmological model which tends to isotropic expansion. 相似文献
11.
12.
D. Lorenz 《Astrophysics and Space Science》1982,85(1-2):59-61
An exact cosmological solution to the Einstein-Maxwell equations for the case of Bianchi type III symmetry with stiff matter and an electromagnetic field is constructed. The behaviour of the solution near the singularity and at late stages of the expansion is investigated. 相似文献
13.
We model a compact relativistic body with anisotropic pressures in the presence of an electric field. The equation of state is barotropic, with a linear relationship between the radial pressure and the energy density. Simple exact models of the Einstein–Maxwell equations are generated. A graphical analysis indicates that the matter and electromagnetic variables are well behaved. In particular, the proper charge density is regular for certain parameter values at the stellar center unlike earlier anisotropic models in the presence of charge. We show that the electric field affects the mass of stellar objects and the observed mass for a particular binary pulsar is regained. Our models contain previous results of anisotropic charged matter with a linear equation of state for special parameter values. 相似文献
14.
The object of this paper is to give a new mathematical and physical method of finding explicit analytical interior solutions of the Einstein-Maxwell field equations of a static perfect fluid sphere with charge. In spite of many successful efforts in solving the field equations, the importance of finding meaningful general analytic solutions remains. Our purpose is to obtain the interior solutions of the field equations that they complete the results, which they have been already published in an earlier paper (Dionysiou, 1982; this paper will be referred to hereafter as Paper I). Using our new formulae, we then rederive some known results as particular solutions. 相似文献
15.
Astrophysical compact stars provide a natural laboratory for testing theoretical models which are otherwise difficult to prove from an experimental setup. In our present work we analyse an exact solution to the Einstein-Maxwell system for a charged anisotropic compact body in the linear regime. The charged parameter may be set to zero which gives us the case of neutral solutions. We have tuned the model parameters for the uncharged case so as to match with recent updated mass-radius estimates for five different compact objects. Then we make a systematic study of the effect of charge for the different parameter set that fits the observed stars. The effect of charge is clearly illustrated in the increase of mass. We show that the physical quantities for the objects PSR J1614-2230, PSR J1903+327, Vela X-1, SMC X-1, Cen X-3 are well behaved. 相似文献
16.
17.
Exact solutions of the semi-classical Einstein equations for conformally invariant free quantum fields in an homogeneous and
isotropic space-time, with cosmological constant and containing a classical scalar field, dust matter, an unquantised Dirac
field and electromagnetic radiation are found. The initial behaviour of the semiclassical models is investigated. Some of
the solutions found avoid the singularity and do not have particle horizons.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
18.
We investigate the behaviour of a charged isotropic model with conformal symmetry. The relationship between the gravitational potentials arising from the conformal condition is used to generate a new class of exact solutions to the Einstein-Maxwell equations. A specific form of the electric field intensity and the metric potential is required to avoid a singularity at the centre. We can find simple elementary functions for the matter variables and the potentials with realistic profiles. The causality conditions, stability conditions and energy conditions are satisfied. Masses, radii, central densities and surface redshifts are generated, and the values are consistent with the compact stars 4U 1538-52 and PSR J1614-2230. 相似文献
19.
Z. Pazameta 《Astrophysics and Space Science》2012,339(2):317-322
Emergent concepts from astroparticle physics are incorporated into a classical solution of the Einstein-Maxwell equations for a binary magnetohydrodynamic fluid, in order to describe the final equilibrium state of compact objects infused with magnetic monopoles produced by proton-proton collisions within the intense dipolar magnetic fields generated by these objects during their collapse. It is found that the effective mass of such an object’s acquired monopolar magnetic field is three times greater than the mass of its native fluid and monopoles combined, necessitating that the interior matter undergo a transition to a state of negative pressure in order to attain equilibrium. Assuming full symmetry between the electric and magnetic Maxwell equations yields expressions for the monopole charge density and magnetic field by direct analogy with their electrostatic equivalents; inserting these into the Einstein equations then leads to an interior metric which is well-behaved from the origin to the surface, where it matches smoothly to an exterior magnetic Reissner-Nordström metric free of any coordinate pathologies. The source fields comprising the model are all described by simple, well-behaved polynomial functions of the radial coordinate, and are combined with straightforward regularity conditions to yield expressions delimiting several fundamental physical parameters pertaining to this hypothetical astrophysical object. 相似文献
20.
Cristian R. Ghezzi 《Astrophysics and Space Science》2011,333(2):437-447
A model of compact object coupled to inhomogeneous anisotropic dark energy is studied. It is assumed a variable dark energy
that suffers a phase transition at a critical density. The anisotropic Λ-Tolman-Oppenheimer-Volkoff equations are integrated
to know the structure of these objects. The anisotropy is concentrated on a thin shell where the phase transition takes place,
while the rest of the star remains isotropic. The family of solutions obtained depends on the coupling parameter between the
dark energy and the fermionic matter. The solutions share several features in common with the gravastar model. There is a
critical coupling parameter that gives non-singular black hole solutions. The mass-radius relations are studied as well as
the internal structure of the compact objects. The hydrodynamic stability of the models is analyzed using a standard test
from the mass-radius relation. For each permissible value of the coupling parameter there is a maximum mass, so the existence
of black holes is unavoidable within this model. 相似文献