Charged Perfect Fluid Research Articles

Physically viable and stable charged perfect fluid solution within [formula omitted] gravity

In this work, we investigate the physical behavior and stability of compact stars in F(Q) gravity. We employ the Buchdahl metric to examine the dynamics of a relativistic, newly charged, isotropic fluid model. The interplay between gravity and electromagnetism is included in the analysis of the system by taking into account the charged state of the fluid, providing insights into how charged fluids behave in gravitational theories. The exterior solution under Schwarzschild–de Sitter (dS) spacetime is linked to the interior solution at the boundary to identify the constants. It is important to note that the Buchdahl ansatz provides a mathematically viable solution for a given transformation in the context of electric charge when pressure and density are maximum in the center and monotonically fall towards the boundary. We have taken into account the compact star Her X-1 with M=(0.85±0.15)M⊙; Radius =13.26−1.08+1.08 km for graphical analysis. In the context of F(Q), the physical acceptability of the model has been examined by looking at the required physical attributes, such as energy conditions, causality, hydrostatic equilibrium, pressure–density ratio, etc. that are satisfied throughout the stellar configuration. It is concluded that the present approach allows a suitable modeling of astrophysical compact objects in F(Q) gravity.

Singularity‐Free Charged Compact Star Model Under F(Q)$F(Q)$‐Gravity Regime

AbstractIn this paper, the possibility of existing a novel class of compact charged spheres based on a charged perfect fluid within the realm of gravity theory is explored. The authors started by proposing physically meaningful explicit formulas for the potential, denoted , and the electric field to find a close‐form solution. More precisely, the change of the dependent variable approach by exploiting the transformation is applied. Successively, the field equations analytically are solved and generate the most general solution, which leads us to examine various significant aspects of the stellar system. These aspects comprise the regularity of gravitational potentials, energy density and pressure, electric charge, the mass‐radius relationship, subluminal sound velocities in the radial direction, and the adiabatic index for charged compact stars. For a more in‐depth system study, mass measurements using contour diagrams are carried out. This mainly involves varying the variable parameters and to distinguish their effect on the mass distribution within the stellar structure. What is more, the electric charge controls the stability of the stellar system is shown, which yields that a stable system can possess a maximum charge of order . The results strongly argue that charged stars could conceivably exist in nature and that such a deviation from traditional theories may be seen in future astrophysical observations.

Dynamic and thermodynamic stability of charged perfect fluid stars

We perform a thorough analysis of the dynamic and thermodynamic stability for the charged perfect fluid star by applying the Wald formalism to the Lagrangian formulation of Einstein–Maxwell-charged fluid system. As a result, we find that neither the presence of the additional electromagnetic field nor the Lorentz force experienced by the charged fluid makes any obstruction to the key steps towards the previous results obtained for the neutral perfect fluid star. Therefore, the criterion for the dynamic stability of our charged star in dynamic equilibrium within the symplectic complement of the trivial perturbations with the Arnowitt-Deser-Misner (ADM) 3-momentum unchanged is given by the non-negativity of the canonical energy associated with the timelike Killing field, where it is further shown for both non-axisymmetric and axisymmetric perturbations that the dynamic stability against these restricted perturbations also implies the dynamic stability against more generic perturbations. On the other hand, the necessary condition for the thermodynamic stability of our charged star in thermodynamic equilibrium is given by the positivity of the canonical energy of all the linear on-shell perturbations with the ADM angular momentum unchanged in the comoving frame, which is equivalent to the positivity of the canonical energy associated with the timelike Killing field when restricted onto the axisymmetric perturbations. As a by-product, we further establish the equivalence of the dynamic and thermodynamic stability with respect to the spherically symmetric perturbations of the static, spherically symmetric isentropic charged star.

Charged strange star model in Tolman–Kuchowicz spacetime in the background of 5D Einstein–Maxwell–Gauss–Bonnet gravity

In this article, we provide a new model of static charged anisotropic fluid sphere made of a charged perfect fluid in the context of 5D Einstein–Maxwell–Gauss–Bonnet (EMGB) gravity theory. To generate exact solutions of the EMGB field equations, we utilize the well-behaved Tolman–Kuchowicz (TK) ansatz together with a linear equation of state (EoS) of the form p_r=beta rho -gamma , (where beta and gamma are constants). Here the exterior space-time is described by the EGB Schwarzschild metric. The Gauss–Bonnet Lagrangian term mathcal {L}_{GB} is coupled with the Einstein–Hilbert action through the coupling constant alpha . When alpha rightarrow 0, we obtain the general relativity (GR) results. Here we present the solution for the compact star candidate EXO 1785-248 with mass=(1.3 pm 0.2)M_{odot }; radius = 10_{-1}^{+1} km. respectively. We analyze the effect of this coupling constant alpha on the principal characteristics of our model, such as energy density, pressure components, anisotropy factor, sound speed etc. We compare these results with corresponding GR results. Moreover, we studied the hydrostatic equilibrium of the stellar system by using a modified Tolman–Oppenheimer–Volkoff (TOV) equation and the dynamical stability through the critical value of the radial adiabatic index.The mass-radius relationship is also established to determine the compactness factor and surface redshift of our model. In this way, the stellar model obtained here is found to satisfy the elementary physical requirements necessary for a physically viable stellar object.

Role of Relativistic Charged Perfect Fluid in Bianchi type-III Space-time in Brans-Dicke theory of gravitation

In this paper, we investigate the role of relativistic charged perfect fluid in Bianchi type-III cosmological model in Brans-Dicke theory of gravitation. Solutions of the model are obtained by volumetric exponential expansion, power law expansion and power law relation between scalar field and the scale factor . Some physical and kinematical properties of the model also are studied.

Effect of electric field on string-oriented perfect fluid collapse in f (R) gravity

This work investigates the nature of singularity formed from string-oriented charged perfect fluid collapse in theory of f (R) gravity. The spherically symmetric spacetime is assumed to be filled with a string-oriented charged perfect fluid. The gravitational collapse of the fluid is analyzed to understand the effects of electric field on the time and radii of apparent horizons and singularity formation. The presence of an electric field was discovered to increase the mass of the collapsing system, the radii of apparent horizon development, and the time gap between the event horizon and singularity. The term [Formula: see text] acts as an anti-gravity term. However, the presence of electric field accelerates the gravitational collapse.

Charged quark stars in f(R,T) gravity* *JMZP acknowledges financial support from the PCI program of the Brazilian agency "Conselho Nacional de Desenvolvimento Científico e Tecnológico"–CNPq. T. Tangphati was supported by King Mongkut's University of Technology Thonburi's Post-doctoral Fellowship. A. Pradhan thanks IUCCA, Pune, India for providing facilities under associateship programmes

Recent advances in nuclear theory and new astrophysical observations have led to the need for specific theoretical models applicable to dense-matter physics phenomena. Quantum chromodynamics (QCD) predicts the existence of non-nucleonic degrees of freedom at high densities in neutron-star matter, such as quark matter. Within a confining quark matter model, which consists of homogeneous, neutral 3-flavor interacting quark matter with corrections, we examine the structure of compact stars composed of a charged perfect fluid in the context of gravity. The system of differential equations describing the structure of charged compact stars has been derived and numerically solved for a gravity model with . For simplicity, we assumed that the charge density is proportional to the energy density, namely, . It is demonstrated that the matter-geometry coupling constant β and charge parameter α affect the total gravitational mass and the radius of the star.

Pulsar PSR B0943$$+$$10 as an isotropic Vaidya–Tikekar-type compact star

In this paper, we have constructed a model for well behaved isotropic compact star in the presence of charged perfect fluid, by considering a static and spherically symmetric metric in Schwarzschild's canonical coordinate system. To put the resulting differential equations into a closed system, we have employed the Vaidya & Tikekar (J. Astrophys. Astron. 3:325, 1982) form of the metric potential grr. The resulting energy-momentum components, i.e., energy density and pressure contain six constants; two of these are determined through the junction condition (matching the interior with the exterior Schwarzschild solution) and by the property of vanishing pressure on the boundary. The remaining constants are constrained by requirements of a real compact star. The physical acceptability of our model is tested using the data of the pulsar PSR B0943+10. Using graphical analysis and tabular information we have shown that our model obeys all the physical requirements. The stability of this model is evaluated using the Tolman-Oppenheimer-Volkoff equation, the adiabatic index and the Harrison-Zeldovich-Novikov Criterion and it has passed the evaluation.

Minimally deformed charged stellar model by gravitational decoupling in 5D Einstein–Gauss–Bonnet gravity

We investigate the possibility of existing a class of compact charged spheres made of a charged perfect fluid in the framework of Einstein–Gauss–Bonnet theory in five-dimensional spacetime (5D EGB). In order to study spherically symmetric compact stars in EGB gravity, we prefer to apply a systematic and direct approach to decoupling gravitational sources via the minimal geometric deformation approach (MGD), which allows us to prove that the fluid must be anisotropic. In fact, we specify a well-known Krori–Barua spacetime in the MGD approach that helps us to determine the decoupling sector completely. Indeed, by using this approach, we found an exact and physically acceptable solution which satisfies all the elementary criteria of physical acceptability for a stellar solution via mimic approach. Finally, we show that the compactness factor in the presence of gravitational decoupling satisfies the Buchdahal limit under 5D EGB gravity.

Thermodynamic equilibrium condition and the first law of thermodynamics for charged perfect fluids in electromagnetic and gravitational fields

We provide a proof of the necessary and sufficient condition on the profile of the temperature, chemical potential, and angular velocity for a charged perfect fluid in dynamic equilibrium to be in thermodynamic equilibrium not only in fixed but also in dynamical electromagnetic and gravitational fields. In passing, we also present the corresponding expression for the first law of thermodynamics for such a charged star.

An isotropic compact stellar model in curvature coordinate system consistent with observational data

This paper investigates a spherically symmetric compact relativistic body with isotropic pressure profiles within the framework of general relativity. In order to solve the Einstein’s field equations, we have considered the Vaidya–Tikekar type metric potential, which depends upon parameter K. We have presented a charged perfect fluid model, considering $$K\notin [0,1]$$ , which represent compact stars like Her X-1, 4U 1538-52, SAX J1808.4-3658, LMC X-4, SMC X-4, EXO 1785-248, Cen X-3 and Cyg X-2, to an excellent degree of accuracy. We have investigated the physical features such as the energy conditions, velocity of sound, surface redshift, adiabatic index of the model in detail and shown that our model obeys all the physical requirements for a realistic stellar model. Using the Tolman–Oppenheimer–Volkoff equations, we have explored the hydrostatic equilibrium and the stability of the compact objects. This model also fulfils the Harrison–Zeldovich–Novikov stability criterion. We have checked the behaviour of the system in the presence of a very high charge (around $$10^{20}$$ Coulomb at surface), which causes an electric field intensity above the Schwinger limit. This amount of charge is mainly caused due to very high density of the system, and a dense system like a compact star can contain such a huge charge. The results obtained in this paper can also be used in analysing other isotropic compact objects.

Charged polytropic compact stars in [formula omitted] Einstein–Gauss–Bonnet gravity

We have investigated the possibility of existing a class of compact charged spheres made of a charged perfect fluid in the context of recently proposed 4D Einstein–Gauss–Bonnet (EGB) gravity theory. The main mechanism is to rescale the Gauss–Bonnet (GB) coupling constant α→α/(D−4) in D dimensions and redefining the 4D gravity in the limit D→4. In this way, the GB term yields a non-trivial contribution to the gravitational dynamics in 4D. Our analysis is based on the assumption of a polytropic equation of state (EoS) and the charge density is taken to be proportional to the energy density. More specifically, we have derived the hydrostatic equilibrium equations in 4D EGB, and we have solved them numerically to obtain mass–radius relations for charged compact stars. Eventually we have found the mass–radius relation depending on the values of the GB coupling constant α and the charge fraction ρch(r). In addition, we have studied the mass vs central mass density (M−εc) relation, which identifies the boundary separating the stable configuration region from the unstable one. We have also obtained a relation between the electric charge inside the stellar region and the maximum mass of compact star in this gravity theory. Finally, we conclude that in such a scenario charged stars may exist in Nature, and that such a deviation may be observable in future astrophysical probes.

Electrically charged quark stars in 4D Einstein\u2013Gauss\u2013Bonnet gravity

In this work we study the properties of compact spheres made of a charged perfect fluid with a MIT bag model EoS for quark matter. Considering static spherically symmetric spacetime we derive the hydrostatic equilibrium equations in the recently formulated four dimensional Einstein–Gauss–Bonnet (4D EGB) gravity theory. In this setting, the modified TOV equations are solved numerically with the aim to investigate the impact of electric charge on the stellar structure. A nice feature of 4D EGB theory is that the Gauss–Bonnet term has a non-vanishing contribution to the gravitational dynamics in 4D spacetime. We therefore analyse the effects of Gauss–Bonnet coupling constant alpha and the charge fraction beta on the mass–radius (M{-}R) diagram and also the mass–central density (M{-}rho _c) relation of quark stars. Finally, we conclude that depending on the choice of coupling constant one could have larger mass and radius compared with GR and can also be relevant for more massive compact objects due to the effect of the repulsive Coulomb force.

Higher-Dimensional Regular Reissner–Nordström Black Holes Associated with Linear Electrodynamics

Following the interpretation of matter source that the energy-momentum tensor of anisotropic fluid can be dealt with effectively as the energy-momentum tensor of perfect fluid plus linear (Maxwell) electromagnetic field, we obtain the regular higher-dimensional Reissner–Nordström (Tangherlini–RN) solution by starting with the noncommutative geometry-inspired Schwarzschild solution. Using the boundary conditions that connect the noncommutative Schwarzschild solution in the interior of the charged perfect fluid sphere to the Tangherlini–RN solution in the exterior of the sphere, we find that the interior structure can be reflected by an exterior parameter, the charge-to-mass ratio. Moreover, we investigate the stability of the boundary under mass perturbation and indicate that the new interpretation imposes a rigid restriction upon the charge-to-mass ratio. This restriction, in turn, permits a stable noncommutative black hole only in the 4-dimensional spacetime.

Plane Symmetry Cosmology Model of Interacting Field in f(R, T) Theory

We have explored a plane symmetric cosmological model in f(R, T) gravity. We have used an interacting field as a source of energy, as well as dark energy. In this case, the interacting field is simply a linear coupling between an electromagnetic field, a massless scalar field, and a charged perfect fluid. Four cases have been described 1) Perfect fluid, 2) Disordered radiation, 3) Dust fluid, and 4) Dark energy. We used the relationship between metric potential to solve field equations. By using equation of state, we observed the pressure and density profiles in various models. We also went over some cosmological and dynamical parameters in depth. Also, we discovered both negative and positive deceleration parameters in different time intervals, indicating the Universe’s transition phase.

Complete deformed charged anisotropic spherical solution satisfying Karmarkar condition

The study of solution for the compact stellar objects such as neutron stars, white dwarfs, and black holes have attracted much consideration in recent days. To discuss this, we extended the charged perfect fluid solution into an anisotropic domain by using the extended gravitational decoupling approach. The charged perfect fluid solution is obtained through the Karmarkar condition by specifying a Finch–Skea spacetime geometry that helps us to determine the decoupling functions. The decoupling function for radial components is determined by using mimic constraint to the seed density while a particular well-behaved function is chosen for the temporal decoupling function. The interior solution is smoothly matched with exterior Reissner–Nordström solution. We found that the obtained charged anisotropic solution is well behaved. In particular, we also studied the impact of gravitational decoupling on pressure, density, mass function, and compactness factor. The detailed physical analysis has been performed via graphical analysis by taking one particular object SMC X-1. Moreover, we have also predicted the radii and compactness factor for 12 compact objects for different values of α. The predicted radii fall between 8 - 15 km.

Dark matter halo with charge in pseudo-spheroidal geometry

The concept of dark matter (DM) hypothesis comes out as a result from the input of the observed flat rotational velocity. With the assumption that the galactic halo is pseudo-spheroidal and filled with charged perfect fluid, we have obtained a solution which has inkling to a (nearly) flat universe, compatible with the modern day cosmological observations. Various other important aspects of the solution such as attractive gravity in the halo region and the stability of the circular orbit are also explored. Also, the matter in the halo region satisfies the known equation of state which indicates its non-exotic nature.

Consistency between dynamical and thermodynamical stabilities for charged self-gravitating perfect fluid

The entropy principle shows that, for self-gravitating perfect fluid, the Einstein field equations can be derived from the extrema of the total entropy, and the thermodynamical stability criterion are equivalent to the dynamical stability criterion. In this paper, we recast the dynamical criterion for the charged self-gravitating perfect fluid in Einstein-Maxwell theory, and further give the criterion of the star with barotropic condition. In order to obtain the thermodynamical stability criterion, first we get the general formula of the second variation of the total entropy for charged perfect fluid case, and then obtain the thermodynamical criterion for radial perturbation. We show that these two stability criterion are the same, which suggest that the inherent connection between gravity and thermodynamic even when the electric field is taken into account.

Analysis of a charged unidirectional perfect fluid gravitational collapse in cylindrical spacetime

The gravitational collapse of charged imperfect fluids (including the presence of strings) models the structural evolution of the Universe. The dynamics of a charged cylindrically symmetric spacetime investigates the effects of charge on the rate of gravitational collapse. In this respect, the Einstein–Maxwell equations are formed and solved to obtain the values of the dynamical parameters of the fluid including density, pressure and electric field. These parameters are graphically presented. It was concluded that the string tension effects all the physical parameters of the fluid. Moreover, the density and electric field intensity increases while the fluid’s pressure decreases near the time of singularity formation.

All fundamental electrically charged thin shells in general relativity: From star shells to tension shell black holes, regular black holes, and beyond

We classify all fundamental electrically charged thin shells in general relativity, i.e., static spherically symmetric perfect fluid thin shells with a Minkowski spacetime interior and a Reissner-Nordstr\"om spacetime exterior, characterized by the spacetime mass and electric charge. The fundamental shell can exist in three states, nonextremal, extremal, and overcharged. The nonextremal state allows the shell to be located such that its radius can be outside its own gravitational radius, or can be inside its own Cauchy radius. The extremal state allows the shell to be located such that its radius can be outside its own gravitational radius, or can be inside it. The overcharged state allows the shell to be located anywhere. There is a further division, one has to specify the orientation of the shell, i.e., whether the normal out of the shell points toward increasing or decreasing radii. There is still a subdivision in the extremal state when the shell is at the gravitational radius, in that the shell can approach it from above or from below. The shell is assumed to be composed of an electrically charged perfect fluid, and the energy conditions are tested. Carter-Penrose diagrams are drawn for the shell spacetimes. There are fourteen cases in the classification of the fundamental shells, namely, nonextremal star shells, nonextremal tension shell black holes, nonextremal tension shell regular and nonregular black holes, nonextremal compact shell naked singularities, Majumdar-Papapetrou star shells, extremal tension shell singularities, extremal tension shell regular and nonregular black holes, Majumdar-Papapetrou compact shell naked singularities, Majumdar-Papapetrou shell quasiblack holes, extremal null shell quasinonblack holes, extremal null shell singularities, Majumdar-Papapetrou null shell singularities, overcharged star shells, and overcharged compact shell naked singularities.