共查询到20条相似文献，搜索用时 30 毫秒
1.
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
2.
Farook Rahaman Mubasher Jamil Ranjan Sharma Kausik Chakraborty 《Astrophysics and Space Science》2010,330(2):249-256
We provide a new class of interior solutions for anisotropic stars admitting conformal motion. The Einstein’s field equations in this construction are solved for specific choices of the density/mass functions. We analyze the behavior of the model parameters like radial and transverse pressures, density and surface tension. 相似文献
3.
4.
N.A. Tomimura 《Astrophysics and Space Science》1997,249(1):31-41
Exact gravitational solutions with radial pressure and heat flow are obtained by integrating the field equations. Junction conditions which match the collapse solutions to the exterior Vaidya metric show that, at the boundary, the pressure is proportional to the magnitude of the heat flow vector. This condition allows us to determine the time-dependent functions of the interior solutions. 相似文献
5.
《New Astronomy》2020
The aim of this paper is to explore a new parametric class of relativistic solutions to the Einstein field equations describing a spherically symmetric, static distribution of anisotropic fluid spheres to study the behavior of some of the cold stars in the setting of Karmarkar space-time continuum. We develop models of stellar objects for a range of parameter values of n and analyze their behavior through graphical representation. For each of these models, we have found that the metric potentials are well behaved inside the stellar interior and the physical parameters such as density, radial and tangential pressures, red-shift, radial speed, radial pressure density ratio and energy conditions display a continuous decrease from the center to surface of the stars whereas the mass, anisotropy, adiabatic indexes and compactification factor show a monotonous increase which imply that the proposed solution satisfy all the physical aspects of a realistic stellar objects. The stability of the solutions are verified by examining various stability aspects, viz., Zeldovich criteria, causality condition, Bondi condition, equilibrium condition (TOV-equation) and stable static criteria in connection to their cogency. 相似文献
6.
V. B. Kuznetsov 《Solar System Research》2016,50(3):211-219
In this paper, the Olbers method for the preliminary parabolic orbit determination (in the Lagrange–Subbotin modification) and the method based on systems of algebraic equations for two or three variables proposed by the author are compared. The maximum number of possible solutions is estimated. The problem of selection of the true solution from the set of solutions obtained both using additional equations and by the problem reduction to finding the objective function minimum is considered. The results of orbit determination of the comets 153P/Ikeya-Zhang and 2007 N3 Lulin are cited as examples. 相似文献
7.
B. C. Tewari 《Astrophysics and Space Science》2012,342(1):73-77
A new class of exact solutions of Einstein’s equations is proposed for a collapsing radiating spherically symmetric shear-free isotropic fluid undergoing radial heat flow. In remote past the solutions are static perfect fluid which then gradually starts evolving into radiating collapse. The interior solutions are matched with Vaidya exterior metric over the boundary. 相似文献
8.
This paper presents a family of two-parametric interior solutions of Einstein–Maxwell field equations in general relativity for a static spherically symmetric distribution of a charged perfect fluid with particular form of charge distribution. This class of solutions gives us wide range of parameters, n and K, for which the solutions are well behaved hence, suitable for modeling of compact star (e. g. bare strange quark star). The mass of star is maximized with all degree of suitability by assuming the stellar “surface” density equal to strange (quark) matter density at zero pressure. It is hoped that our investigation may be of some help in connection of some study of stellar structure. 相似文献
9.
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
10.
B. C. Tewari 《Astrophysics and Space Science》1988,149(2):233-239
In this paper Einstein's field equations for spherically-symmetric radiating fluid distributions are discussed and some new exact regular solutions are obtained. 相似文献
11.
Recently, Bijalwan (Astrophys. Space Sci. doi:, 2011) discussed all important solutions of charged fluid spheres with pressure and Gupta et al. (Astrophys. Space Sci. doi:, 2010) found first closed form solutions of charged Vaidya-Tikekar (V-T) type super-dense star. We extend here the approach evolved
by Bijalwan (Astrophys. Space Sci. doi:, 2011) to find all possible closed form solutions of V-T type super-dense stars. The existing solutions of Vaidya-Tikekar type
charged fluid spheres considering particular form of electric field intensity are being used to model massive stars. Infact
at present maximum masses of the star models are found to be 8.223931M
Θ and 8.460857M
Θ subject to ultra-relativistic and non-relativistic conditions respectively. But these stars with such are large masses are
not well behaved due to decreasing velocity of sound in the interior of star. We present new results concerning the existence
of static, electrically charged perfect fluid spheres that have a regular interior. It is observed that electric intensity
used in this article can be used to model superdense stars with ultrahigh surface density of the order 2×1014 gm/cm3 which may have maximum mass 7.26368240M
Θ for ultra-relativistic condition and velocity of sound found to be decreasing towards pressure free interface. We solve the
Einstein-Maxwell equations considering a general barotropic equation of state with pressure. For brevity we don’t present
a detailed analysis of the derived solutions in this paper. 相似文献
12.
In the present paper we study some new aspects of the Bianchi type-V space time. The Electric and Magnetic parts of Weyl tensors are calculated in terms of tilted congruence and discussed the purely magnetic Weyl tensor. Einstein field equations for purely magnetic space time are obtained and solution of such field equations called purely magnetic solution. To get deterministic solutions of the field equations we consider a new law of variation of average scale factor which yields time dependent deceleration parameter. Certain physical and geometrical properties of the model are also discussed. 相似文献
13.
A numerical method is presented for finding the magnetic field in the transition region between the bow shock and the effective obstacle in steady state three dimensional solar wind flow around a planet. On assuming that the Alfven-Maeh number is very large there is decoupling into a gasdynamic problem and an electromagnetic problem. After solving the gasdynamic problem in the axisymmetric formulation, the equations for the magnetic field are also solved numerically. A comparison with earlier solutions is made. The results are discussed from the point of view of their possible use in the interpretation of satellite data. 相似文献
14.
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
15.
We investigate the effect of a strong large-scale magnetic field on the reflection of high-frequency acoustic modes in rapidly oscillating Ap stars. To that end, we consider a toy model composed of an isothermal atmosphere matched on to a polytropic interior and determine the numerical solution to the set of ideal magnetohydrodynamic equations in a local plane-parallel approximation with constant gravity. Using the numerical solution in combination with approximate analytical solutions that are valid in the limits where the magnetic and acoustic components are decoupled, we calculate the relative fraction of energy flux that is carried away in each oscillation cycle by running acoustic waves in the atmosphere and running magnetic waves in the interior. For oscillation frequencies above the acoustic cut-off, we show that most energy losses associated with the presence of running waves occur in regions where the magnetic field is close to vertical. Moreover, by considering the depth dependence of the energy associated with the magnetic component of the wave in the atmosphere we show that a fraction of the wave energy is kept in the oscillation every cycle. For frequencies above the acoustic cut-off frequency, such energy is concentrated in regions where the magnetic field is significantly inclined in relation to the local vertical. Even though our calculations were aimed at studying oscillations with frequencies above the acoustic cut-off frequency, based on our results we discuss what results may be expected for oscillations of lower frequency. 相似文献
16.
《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
17.
G. F. Roach 《Astrophysics and Space Science》1981,80(1):237-247
A method, involving boundary integral equations of the first kind is offered for obtaining exact representations for solutions to interior and exterior harmonic problems. The method is constructive and a representation can be obtained to any degree of accuracy. The determination of Roche harmonics appears as a special case. 相似文献
18.
F. Váradi 《Celestial Mechanics and Dynamical Astronomy》1993,57(4):517-536
Branching solutions of algebraic equations are treated using Lie series. A new method is proposed to derive Puiseux expansions. Newton's diagram is considered in the context of Lie series. An application of finding equilibrium points of a Hamiltonian system near resonances is also demonstrated. 相似文献
19.
The general solution of the Einstein equation for higher dimensional (HD) spherically symmetric collapse of inhomogeneous
dust in presence of a cosmological term, i.e., exact interior solutions of the Einstein field equations is presented for the
HD Tolman–Bondi metrics embedded in a de Sitter background. The solution is then matched to exterior HD Schwarzschild–de Sitter.
A brief discussion on the causal structure singularities and horizons is provided. It turns out that the collapse proceed
in the same way as in the Minkowski background, i.e., the strong curvature naked singularities form and that the higher dimensions
seem to favor black holes rather than naked singularities.
相似文献
20.
《New Astronomy》2021
In this paper, we present two new exact and analytic solutions of the Einstein–Maxwell field equations describing compact anisotropic charged stars satisfying the Karmarkar condition in the background of Bardeen black hole geometry. The solutions are composed of two parts: The inner region of the star is described by class I Karmarkar space-time, while exterior of the star is characterized by both the Bardeen and the Reissner–Nordstrom space-times. Physical analysis of the matter and thermodynamical variables show that the models are well-behaved. For our parametric set of values, we conclude that the Bardeen black hole metric can be used as an alternate to the exterior Reissner–Nordstrom metric. 相似文献