Electromagnetic Mass Models Research Articles

Analysis of charged gravastar in f(R,G) gravity

This paper is dedicated to inspecting the appearance of electromagnetic field, which is caused by the presence of charge in the highly compact object named gravastar in the background of [Formula: see text] theory. According to conjecture introduced by Mazur and Mottola gravastar must be consisted of three sectors. We have interpreted these sectors by using specific equations of states. Spherically static metric, perfect fluid and the isotropic pressure have been used in order to calculate a singularity free solution. Gravitational mass present in the inner sector of gravastar is changed into electromagnetic mass in the existence of charge. The electromagnetic mass model of inner sector is responsible for stability by providing balance to the repulsive pressure, which is caused by the presence of charge. It is observed that the presence of electrical charge has a significant effect on energy content, entropy and proper length of the shell that is demonstrated with the help of graphs.

A study on charged compact stars

In this paper, the Einstein–Maxwell spacetime is considered for compact stellar system. To find out solutions of the field equations, we adopt a finite and positive well-behaved metric potential. Under this particular choice, we therefore develop the expressions of the physical features, such as mass, charge, density and pressure, for stellar system in embedding class 1 spacetime. It is observed that all these features are physically viable. In the model, some known compact stars, viz. [Formula: see text] 1820–30, [Formula: see text] 1608–52 and [Formula: see text] 1745–248 [Formula: see text] are studied successfully through physical analysis. It is also interesting to note that the obtained set of regular solutions to the Einstein–Maxwell equations represents an electromagnetic mass model for isotropic fluid without invoking any negative pressure.

Relativistic electromagnetic mass models in spherically symmetric spacetime

Under the static spherically symmetric Einstein-Maxwell spacetime of embedding class one we explore possibility of electromagnetic mass model where mass and other physical parameters have purely electromagnetic origin (Tiwari 1984, Gautreau 1985, Gron 1985). This work is in continuation of our earlier investigation (Maurya 2015a) where we developed an algorithm and found out three new solutions of electromagnetic mass models. In the present letter we consider different metric potentials $\nu$ and $\lambda$ and analyzed them in a systematic way. It is observed that some of the previous solutions related to electromagnetic mass models are nothing but special cases of the presently obtained generalized solution set. We further verify the solution set and show that these are extremely applicable in the case of compact stars as well as for understanding structure of the electron.

Static charged fluid in (2 + 1)-dimensions admitting conformal Killing vectors

New solutions for (2 + 1)-dimensional Einstein–Maxwell spacetime are found for a static spherically symmetric charged fluid distribution with the additional condition of allowing conformal Killing vectors (CKV). We discuss physical properties of the fluid parameters. Moreover, it is shown that the model actually represents two structures, namely (i) Gravastar as an alternative of black hole and (ii) Electromagnetic Mass model depending on the nature of the equation of state of the fluid. Here the gravitational mass originates from electromagnetic field alone. The solutions are matched with the exterior region of the Bañados–Teitelboim–Zanelli (BTZ) type isotropic static charged black hole as a consequence of junction conditions. We have shown that the central charge density is dependent on the value of M0, the conserved mass of the BTZ black hole. This, in turn, depends on the black hole event horizon which again is related to the Hawking radiation temperature of a BTZ black hole. Thus, one may have a clue that the central charge density is related with Hawking radiation temperature of the BTZ black hole on the exterior region of the static charged fluid sphere.

Charged gravastars admitting conformal motion

We propose a new model of a gravastar admitting conformal motion. While retaining the framework of the Mazur–Mottola model, the gravastar is assumed to be internally charged, with an exterior defined by a Reissner–Nordström instead of a Schwarzschild line element. The solutions, obtained by exploiting an assumed conformal Killing vector, involve (i) the interior region, (ii) the shell, and (iii) the exterior region of the sphere. Of these three cases the first one is of primary interest since the total gravitational mass here turns out to be an electromagnetic mass under some specific conditions. This suggests that the interior de Sitter vacuum of a charged gravastar is essentially an electromagnetic mass model that must generate gravitational mass which provides a stable configuration by balancing the repulsive pressure arising from charge with its attractive gravity to avert a singularity. Therefore the present model, like the Mazur–Mottola model, results in the construction of a compact astrophysical object, as an alternative to a black hole. We have also analyzed various other aspects such as the stress energy tensor in the thin shell and the entropy of the system.

CHAPLYGIN ELECTRON GAS MODEL

We provide a new electromagnetic mass model admitting the Chaplygin gas equation of state. We investigate three specializations, the first characterized by a vanishing effective pressure, the second provided with a constant effective density and the third described by a constant effective pressure p0. For these specializations we will discuss the models assuming that [Formula: see text], where σ, σ0, λ and s represent the charge density of the spherical distribution, the charge density at the center of the system, the metric potential and a constant, respectively. In addition, for specialization I, we have found the isotropic coordinate as well as the Kretschmann scalar for a particular case, and for specialization III two special scenarios have been studied.

Relativistic anisotropic charged fluid spheres with varying cosmological constant

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.

PHYSICAL PROPERTIES OF TOLMAN–BAYIN SOLUTIONS: SOME CASES OF STATIC CHARGED FLUID SPHERES IN GENERAL RELATIVITY

In this article, Einstein–Maxwell space–time is considered in connection with some of the astrophysical solutions previously obtained by Tolman (1939) and Bayin (1978). The effect of inclusion of charge in these solutions is investigated thoroughly and the nature of fluid pressure and mass density throughout the sphere is discussed. Mass–radius and mass–charge relations are derived for various cases of the charged matter distribution. Two cases are obtained where perfect fluid with positive pressures gives rise to electromagnetic mass models such that gravitational mass is of purely electromagnetic origin.

ELECTROMAGNETIC MASS IN (n + 2)-DIMENSIONAL SPACE–TIMES

Einstein–Maxwell field equations corresponding to a higher-dimensional description of static spherically symmetric space–time are solved under two specific sets of conditions: (i) ρ ≠ 0, ν′ = 0 and (ii) ρ = 0, ν′ ≠ 0, where ρ and ν represent the mass density and metric potential. The solution sets thus obtained satisfy the criteria of being an electromagnetic mass model such that the gravitational mass vanishes for the vanishing charge density σ and also the space–time becomes flat. Physical features related to other parameters are also discussed.

Relativistic Electromagnetic Mass Models: Charged Dust Distribution in Higher Dimensions

Electromagnetic mass models are proved to exist in higher dimensional theory of general relativity corresponding to charged dust distribution. Along with the general proof a specific example is also sited as a supporting candidate.

Static Spherically Symmetric Electromagnetic Mass Models with Charged Dust Sources in Einstein-Cartan Theory: Lane-Emden Models

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.

A class of axially-symmetric electromagnetic mass models

This paper presents a set of solutions of coupled Einstein-Maxwell equations with matter for the Levi-Civita's metric which can be interpreted as electromagnetic mass models which are extensions of the electromagnetic mass models obtained previously. It may be pointed out that electromagnetic mass models are solutions of coupled Einstein-Maxwell equations with matter where all the characteristics of matter vanish when the charge vanishes. Existence of such solution tends to confirm Lorentz's conjecture that the mass of an electron may be of purely electromagnetic origin.

Spherically symmetric electromagnetic mass models with cosmological parameter ?

An exact solution has been obtained for the Einstein-Maxwell field equation with ⋀ corresponding to a spherically-symmetric charged perfect fluid distribution. Here the cosmological constant ⋀ is assumed to be a scalar variable depending on the radial coordinater of the spherical system, viz., ⋀ = ⋀(r). The solution set thus obtained presents an electromagnetic mass model.

Gravitational sources of purely electromagnetic origin

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 potentialsgij 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-Nordstrom-Curzon’ field (an analogue of the Reissner-Nordstrom solution obtained by Curzon) which according to Curzon describes the exterior field of an electron.

Spherically-symmetric gravitational sources of purely electromagnetic origin

The present paper is a continuation of our earlier work on gravitational sources of purely electromagnetic origin, known in the literature as electromagnetic mass models. Here we have shown that a bounded (regular) interior static sperical-symmetric charged dust, if exists, can only be of electromagnetic origin.

General relativistic electromagnetic mass models of neutral spherically symmetric systems

The recent work of Gron [1] concerning charged analogues of Florides' class of solutions is discussed and generalized. The properties of this kind of model are investigated. In particular it is shown that the ratiom/r as well as the acceleration of gravity are maximum inside the body rather than at the boundary. Some exact solutions of the Einstein-Maxwell equations illustrating these properties are presented. The solutions are matched continuously to the exterior Schwarzschild solution and they represent electromagnetic mass models of neutral systems. All physical quantities are finite inside the distributions. The energy density is positive and decreases monotonically from its maximum value at the center to zero at the boundary.

Electromagnetic mass models in general relativity: Lane-Emden-type models.

Imposing an equation of state rho+p-italic = 0, rho>0 (''false vacuum'') on a static spherically symmetric charged perfect-fluid distribution, various electromagnetic mass models are derived. It is shown that the modified field equations suggested by Einstein to study the equilibrium structure of an ''electron'' form a part of the field equations considered by us in this paper. Assuming an implicit relation among the unknown physical parameters, viz., the pressure p-italic, charge density sigma, and the electromagnetic potential Phi, it is shown that Phi satisfies the well-known Lane-Emden equation. Electromagnetic mass models corresponding to the exact solutions of the Lane-Emden equation are obtained. The radii of some of the models are compared with the ''classical electron radius.''

A charged generalization of Florides' interior Schwarzschild solution

The new class of interior Schwarzschild solutions found by Florides is generalized to the charged case. A particular solution within this class is found, which represents an electromagnetic mass-model of a neutral spherically symmetric system. The pressure is isotropic, decreasing monotonously with increasing radius and vanishes at the surface of the matter distribution. The solution is regular everywhere inside a radiusR, and is joined continuously to the exterior Schwarzschild solution at this radius.

Repulsive gravitation and electron models.

Poincar\'e stresses are explained as due to vacuum polarization in connection with a recently presented class of electromagnetic mass models in general relativity. The gravitational blue-shift of light, noted in an earlier solution of the Einstein-Maxwell equations, is explained as due to repulsive gravitation produced by the negative gravitational mass of the polarized vacuum. It is pointed out that the electron model of Lopez, which includes spin, and which is a source of the Kerr-Newman field, gives rise to repulsive gravitation.

Electromagnetic mass model of a static charged perfect fluid sphere

Using the results, which they have been already published in two earlier papers (Dionysiou, 1982; Dionysiou and Kostakis, 1983; these papers will hereafter be referred to as Papers I, II, respectively), one can easily see that the total gravitational mass, the density and pressure of a static charged perfect fluid sphere are of electromagnetic origin.