Charged Gravastars Research Articles

Charged gravastar in f(R,Σ,T)-gravity

Charged gravastar in f(R,Σ,T)-gravity

Charged gravastar model in noncommutative geometry under [formula omitted] gravity

In this article, we study the properties of charged gravastars in torsion-based f(T) gravity in the presence of noncommutative geometry. We have taken the interior from noncommutative motivated space–time, noting that why, from a physical point of view, such a choice is justified, then we have taken the thin shell as stiff matter and taken three different exterior metrics (Reissner–Nordstrom (R–N), Bardeen and Ayon-Beato–Garcia (ABG) metric) to construct the gravastar model. We have studied the physical properties like proper length, entropy, energy, and EoS for these models, and we have also used Israel junction conditions to study the effective pressure, energy density, and potential of the thin shell. Finally, we comment on the stability of such a thin shell and the deflection angle caused by such a thin shell, which could, in principle, be tested by future radio telescopes like the Event Horizon Telescope (EHT).

Constraining study of charged gravastars solutions in symmetric teleparallel gravity

This study explores the effect of charge on a special astronomical object known as a gravastar, which is viewed as an alternative to a black hole. Based on the conjecture put out by Mazur and Mottola in general relativity, the study primarily focuses on the consequences of f(Q) gravity. The internal domain, the intermediate shell, and the external domain are the three separate sections that make up a gravastar. Using a particular f(Q) gravity model that includes conformal Killing vectors to analyze these areas, we discover that the inner domain shows a repulsive force on the spherical shell since it is assumed that pressure is equivalent to negative energy density. The intermediate shell is made up of ultrarelativistic plasma and pressure, which is proportional to energy density and balances the repulsive force from the interior domain. For the exterior region, we use two approaches first we calculate the vacuum exact solution, and second, consider the Reissner–Nordström metric. Then, we match these spacetimes through junction conditions and explore the stability constraints for both cases. Our results show that charged gravastar solutions with non-singular physical parameters including length, energy, entropy, and equation of state parameter are physically realistic.

Charged gravastars with conformal motion in the Finslerian space-time

In this article, we investigate the charged gravastar under conformal motion with the background of Finsler geometry. Mazur and Mottola pioneered the concept of the gravastar (gravitational vacuum star) for the first time. This vacuum object consists of three distinct regions, that is, (i) interior de Sitter region, (ii) thin shell consisting of ultrarelativistic stiff, and (iii) exterior vacuum Schwarzschild region. The nature of these regions can be analyzed by considering different equations of state parameters. We have studied various physical features of the gravastar, such as length, energy, entropy, stability, and the adiabatic index, both graphically and analytically within the Finslerian framework. Also, we have obtained the exact and non-singular solution for the gravastar model.

Study of charged gravastar model in [formula omitted] gravity

In recent days gravastar has been a very lucrative alternative to black holes, as it does not suffer from the singularity problem as well and it is based on sound physical grounds. Modified Symmetric teleparallel equivalent of gravity also has seen quite a few successes in recent years both in cosmology as well as in astrophysical objects like black holes and wormholes. In this paper, we have considered the charged gravastar in f(Q) formulation and have solved it fully analytically and found various physical characteristics like energy density, entropy and EoS for the gravastar. We have used the Israel junction condition to make some phenomenological predictions regarding the potential of the thin shell around the gravastar. We have also studied the deflection of the angle caused by the gravastar. Finally, we conclude by noting how future radio telescopes could detect the gravastar shadow and how can one distinguish it from the black hole event horizon.

Stable gravastars with Krori–Barua metric in [formula omitted] gravity

This paper deals with the physical attributes of charged gravastar in the realm of f(R,T2) gravity. The hypothetical gravastar structure is an alternative of black hole. The gravastar geometry has three sectors, namely the internal and external domains with shell region behaving as a separating layer between internal and external regions. We utilize distinct values of the equation of state parameter corresponding to each of these three regions. We construct gravastar structure incorporating a specific model of the considered theory. We formulate the field equations for a static sphere with charged isotropic matter configuration. Israel matching criteria is employed to assure smooth joining of both inner as well as outer geometries. We discuss various gravastar attributes versus shell thickness (length, entropy as well as energy) in the presence of charge. In the inner core, charge provides repulsive force counteracting the gravitational force acting inward and thus the equilibrium state of gravastar is preserved. We conclude that charged gravastar structure provides an acceptable behavior in this modified theory of gravity.

Impact of charge on gravastars in f(ℜ,𝒯2) gravity

This paper studies the influence of charge on a compact stellar structure also regarded as vacuum condensate star in the background of [Formula: see text] gravity. This object is considered the alternate of black hole whose structure involves three distinct regions, i.e. interior, exterior and thin-shell. We analyze these domains of a gravastar for a particular model of this modified theory. In the inner region of a gravastar, the considered equation of state defines that energy density is equal to negative pressure which is the cause of repulsive force on the spherical shell. In the intermediate shell, pressure and energy density are equal and contain ultra-relativistic fluid. The inward-directed gravitational pull of thin-shell counterbalances the force exerted by the inner region of a gravastar allowing the formation of a singularity-free object. The Reissner–Nordström metric presents the outer vacuum spherical domain. Moreover, we discuss the impact of the charge on physical attributes of a gravastar such as the equation of state parameter, entropy, proper length and energy. We conclude that singularity-free solutions of charged gravastar are physically consistent in this modified theory.

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.

Charged gravastars in modified Gauss–Bonnet gravity

This work probes the influence of charge field on the unique stellar structure, regarded as gravastar, under the corrections of [Formula: see text] theory, i.e. [Formula: see text] theory, where [Formula: see text] is named as Gauss–Bonnet invariant. The gravastar has also been recognized as an alternate candidate of black hole structure and is illustrated by three distinct regions termed as (1) the exterior (2) the intermediate thin shell (3) the interior domain. We discussed the mathematical solutions for each of three regions separately with the assistance of different equation-of-states (EoS). The exterior charged vacuum domain is expressed by the Reissner–Nordström solution. The central region is illustrated by the EoS, i.e. a positive pressure of ultra-relativistic matter is equal to the energy density. Whereas, the interior domain reflects that the negative pressure is equal to energy density and manifests a non-attractive force over the central spherical shell. We deduce that in the context of [Formula: see text] theory, the nonsingular charged model with distinct physical features, such as energy, length, entropy, is physically viable and consistent.

Charged gravastars in f(R,T,RμνTμν) gravity

We explore the aspects of the electromagnetism on the stability of gravastar in a particular modified theory, i.e. [Formula: see text] where [Formula: see text], [Formula: see text] is the Ricci scalar and [Formula: see text] is the trace of energy–momentum tensor. We assume a spherically symmetric static metric coupled comprising of perfect fluid in the presence of electric charge. The purpose of this paper is to extend the results of [S. Ghosh, F. Rahaman, B. K. Guha and S. Ray, Phys. Lett. B 767 (2017) 380.] to highlight the effects of [Formula: see text] gravity in the formation of charged gravastars. We demonstrated the mathematical formulation, utilizing different equations of state, for the three respective regions (i.e. inner, shell, exterior) of the gravastar. We have matched smoothly the interior de Sitter and the exterior Reissner–Nordström metric at the hypersurface. At the end we extracted few conclusions by working on the physical features of the charged gravastar, mathematically and graphically.

Charged gravastar model in f(T) gravity admitting conformal motion

In this paper, model of charged gravastar under [Formula: see text] modified gravity is obtained. The model has been explored by taking the diagonal tetrad field of static spacetime together with electric charge. To solve the Einstein–Maxwell field equations, along with [Formula: see text] gravity, we assume the existence of a conformal Killing vector which relates between geometry and matter through the Einstein–Maxwell field equations by an inheritance symmetry. We study several cases of interest to explore physically valid features of the solutions. Some physical properties of the model are discussed and we match our interior spacetime to the exterior Reissner–Nordström spacetime in presence of thin shell.

Charged gravastars in Rastall-Rainbow gravity

In this work, we have assumed the spherically symmetric stellar system in the contexts of Rastall-Rainbow gravity theory in the presence of isotropic fluid source with electro-magnetic field. Einstein-Maxwell’s field equations have been written in the framework of Rastall-Rainbow gravity. Next, we have discussed the geometry of charged gravastar model. The gravastar consists of three regions: interior region, thin shell region, and exterior region. In the interior region, the gravastar follows the equation of state (EoS) \(p=-\rho \), and we have found the solutions of all physical quantities like energy density, pressure, electric field, charge density, gravitational mass, and metric coefficients. In the exterior region, we have obtained the exterior Riessner-Nordstrom solution for vacuum model (\(p=\rho =0\)). Since in the shell region, the fluid source follows the EoS \(p=\rho \) (ultra-stiff fluid) and the thickness of the shell of the gravastar is infinitesimal, so by the approximation \(h~(\equiv A^{-1})\ll 1\), we have found the analytical solutions within the thin shell. The physical quantities like the proper length of the thin shell, entropy, and energy content inside the thin shell of the charged gravastar have been computed, and we have shown that they are directly proportional to the proper thickness of the shell (\(\epsilon \)) due to the approximation \(\epsilon \ll 1\). The physical parameters significantly depend on the Rastall parameter and Rainbow function. Next, we have studied the matching between the surfaces of interior and exterior regions of the charged gravastar, and using the matching conditions, the surface energy density and the surface pressure have been obtained. Also, the equation of state parameter on the surface, mass of the thin shell, mass of the gravastar have been calculated. Finally, we have explored the stability of the charged gravastar in Rastall-Rainbow gravity.

Effects of electromagnetic field on the stability of locally isotropic gravastars

We have studied a new solution of charged gravastars with isotropic matter configuration in the framework of f(R, T) theory of gravity. For this purpose, we have assumed the electric charge as a constant. This stellar structure divided into three different regions: The preliminary part shows the interior charged region in which pressure equals to the negative density, second is the intermediate charged shell which is assumed to be very thin and filled with ultrarelativistic stiff fluid and the last corresponds to the electrovacuum region which is defined by an exterior Reissner-Nordström solution. Under these assumptions, we have found some physical aspects like length, energy, entropy and equation of state for charged spherical gravastar distribution. Moreover, we present an exact solution that free from event horizon and non-singular for this our new model.

Charged gravastars with cylindrical spacetime

The objective of this work is to construct a gravastar model using thin-shell formalism and discuss its realistically accepted properties with the background of cylindrical metric. In this scenario, we matched the interior cylindrical geometry with exterior metric via Israel matching conditions. The stability of the constructed model under the influence of electric charge is then examined using linear perturbations around the equilibrium condition. We explored some stable regimes near the equilibrium condition with different values of charge as well as involved parameters.

Charged gravastars with conformal motion in $f(R,T)$ gravity

This paper studies the effects of charge on a peculiar stellar object, recognized as gravastar, under the influence of $f(R,T)$ gravity by considering the conjecture of Mazur and Mottola in general relativity. The gravastar is also known as an alternative to a black hole and is expressed by three distinct domains named as (i) the interior domain, (ii) the intermediate shell and (iii) the exterior domain. We analyze these domains for a specific $f(R,T)$ gravity model conceding the conformal Killing vectors. In the interior domain, we assume that pressure is equal to negative energy density which leads to the existence of repulsive force on the spherical shell. The intermediate shell consists of ultra-relativistic plasma and pressure which shows a direct relation with energy density and counterbalances the repulsive force applied by the interior domain. The exterior vacuum spherical domain is taken to be the de Sitter spacetime illustrated by the Reissner-Nordstr\"{o}m metric. We conclude that non-singular solutions of charged gravastar with various physical properties such as length, energy, entropy and equation of state parameter are physically consistent.

Charged gravastars in modified gravity

In this paper, we investigate the effects of electromagnetic field on the isotropic spherical gravastar models in metric $f(R,T)$ gravity. For this purpose, we have explored singularity-free exact models of relativistic spheres with a specific equation of state. After considering Reissner Nordstr\"{o}m spacetime as an exterior region, the interior charged manifold is matched at the junction interface. Several viable realistic characteristics of the spherical gravastar model are studied in the presence of electromagnetic field through graphical representations. It is concluded that the electric charge has a substantial role in the modeling of proper length, energy contents, entropy and equation of state parameter of the stellar system. We have also explored the stable regions of the charged gravastar structures.

Charged thin-shell gravastars in noncommutative geometry

In this paper we construct a charged thin-shell gravastar model within the context of noncommutative geometry. To do so, we choose the interior of the nonsingular de Sitter spacetime with an exterior charged noncommutative solution by cut-and-paste technique and apply the generalized junction conditions. We then investigate the stability of a charged thin-shell gravastar under linear perturbations around the static equilibrium solutions as well as the thermodynamical stability of the charged gravastar. We find the stability regions, by choosing appropriate parameter values, located sufficiently close to the event horizon.

Charged gravastars in higher dimensions

We explore possibility to find out a new model of gravastars in the extended $D$-dimensional Einstein-Maxwell spacetime. The class of solutions as obtained by Mazur and Mottola of a neutral gravastar \cite{Mazur2001,Mazur2004} have been observed as an alternative to $D$-dimensional versions of the Schwarzschild-Tangherlini black hole. To tackle the spherical system in a convenient way we have configured that the gravastar consists of three distinct regions with different equations of state as follows: [I] Interior region $0 \leq r < r_1$,$\rho = -p$, [II] Thin shell region $r_1 \leq r < r_2$,$\rho = p$, and [III] Exterior region $r_2 < r$,$\rho = p =0$. The outer region of this gravastar model therefore corresponds to a higher dimensional Reissner-Nordstr{\"o}m black hole. In connection to this junction conditions are provided and therefore we have formulated mass and the related Equation of State of the gravastar. It has been shown that the model satisfies all the requirements of the physical features. However, overall observational survey of the results also provide probable indication of non-applicability of higher dimensional approach for construction of a gravastar with or without charge from an ordinary $4$-dimensional seed as far as physical ground is concerned.

Charged Gravastar in a Dark Energy Universe

Here we constructed a charged gravastar model formed by an interior de Sitter spacetime, a charged dynamical infinitely thin shell with an equation of state and an exterior de Sitter-Reissner-Nordstr\"om spacetime. We find that the presence of the charge is crucial to the stability of these structures. It can as much favor the stability of a bounded excursion gravastar, and still converting it in a stable gravastar, as make disappear a stable gravastar, depending on the range of the charge considered. There is also formation of black holes and, above certain values, the presence of the charge allows the formation of naked singularity . This is an important example in which a naked singularity emerges as a consequence of unstabilities of a gravastar model, which reinforces that gravastar is not an alternative model to black hole.

The [formula omitted]-dimensional charged gravastars

This is a continuation and generalization of our earlier work on gravastar in (2+1) anti-de Sitter space–time to (2+1)-dimensional solution of charged gravastar. Morphologically this gravastar contains three regions, namely: (i) charged interior, (ii) charged shell and (iii) electrovacuum exterior. We have studied different characteristics in terms of Length and Energy, Entropy, and Junction conditions of the spherical charged distribution. It is shown that the present model of charged gravastar is non-singular and represents itself an alternative of black hole.