scholarly journals Gravitational collapse of compact stars in f(R) = ξR4 gravity

2021 ◽  
Author(s):  
Jay Solanki
Keyword(s):  
Gravity Model ◽  
Gravitational Collapse ◽  
Analytical Solutions ◽  
Modified Gravity ◽  
Compact Stars ◽  
Physical Parameters ◽  
Field Equations ◽  
Paper Model ◽  
Acceptable Model ◽  
Physical Quantities

In this paper, model of gravitational collapse of anisotropic compact stars in a new theory of [Formula: see text] gravity has been developed. The author considers the modified gravity model of [Formula: see text] to investigate a physically acceptable model of gravitational collapse of anisotropic compact stars. First, the author presents a brief review of the development of field equations of gravitational collapse in [Formula: see text] gravity for a particular interior metric for compact stars. Then analytical solutions for various physical quantities of collapsing anisotropic compact stars in [Formula: see text] gravity have been developed. By analyzing plots of various physical parameters and conditions, it is shown that the model is physically acceptable for describing the gravitational collapse of anisotropic compact stars in [Formula: see text] gravity.

Color-flavor locked compact stars: An exact solution approach

2021 ◽  
Author(s):  
Ksh. Newton Singh ◽  
Shyam Das ◽  
Piyali Bhar ◽  
Monsur Rahaman ◽  
Farook Rahaman
Keyword(s):  
Exact Solution ◽  
Compact Star ◽  
Density Perturbation ◽  
Compact Stars ◽  
Stable Configuration ◽  
Physical Parameters ◽  
Superconducting Gap ◽  
Field Equations ◽  
Critical Limit ◽  
Solution Approach

We present an exact solution that could describe compact star composed of color-flavor locked (CFL) phase. Einstein’s field equations were solved through CFL equation of state (EoS) along with a specific form of [Formula: see text] metric potential. Further, to explore a generalized solution we have also included pressure anisotropy. The solution is then analyzed by varying the color superconducting gap [Formula: see text] and its effects on the physical parameters. The stability of the solution through various criteria is also analyzed. To show the physical validity of the obtained solution we have generated the [Formula: see text] curve and fitted three well-known compact stars. This work shows that the anisotropy of the pressure at the interior increases with the color superconducting gap leading to decrease in adiabatic index closer to the critical limit. Further, the fluctuating range of mass due to the density perturbation is larger for lower color superconducting gap leading to more stable configuration.

scholarly journals Analysis of charged compact stars in modified gravity

2018 ◽  
Vol 27 (08) ◽  
pp. 1850082 ◽  
Author(s):  
M. Farasat Shamir ◽  
Saeeda Zia
Keyword(s):  
Modified Gravity ◽  
Compact Star ◽  
Compact Object ◽  
Relative Difference ◽  
Comprehensive Analysis ◽  
Compact Stars ◽  
Energy Conditions ◽  
Anisotropic Pressure ◽  
Field Equations ◽  
Stability Energy

Current study highlights the physical characteristics of charged anisotropic compact stars by exploring some exact solutions of modified field equations in [Formula: see text] gravity. A comprehensive analysis is performed from the obtained solutions regarding stability, energy conditions, regularity, sound velocity and compactness. These solutions can be referred to model the compact celestial entities. In particular, a compact star named, [Formula: see text] has been modeled which indicates that current solution fits and is in conformity to the observational data as well. A useful and interesting fact from this model arises that relative difference between two forces of anisotropic pressure and electromagnetic force may occur inside the aforementioned compact star. This is another mechanism which is essential for stability of the compact object and prevent stellar object to annihilate.

scholarly journals First-order perturbations of Gödel-type metrics in non-dynamical Chern-Simons modified gravity

2021 ◽  
Author(s):  
Brett D Altschul ◽  
J Roberto S Nascimento ◽  
A Yu Petrov ◽  
P. J. Porfı́rio
Keyword(s):  
Analytical Solutions ◽  
Effective Potential ◽  
Modified Gravity ◽  
Perturbation Parameter ◽  
Field Equations ◽  
Schwarzschild Metric ◽  
First Order ◽  
Space And Time ◽  
Massive Particles ◽  
Chern Simons

Abstract G\"{o}del-type metrics that are homogeneous in both space and time remain, like the Schwarzschild metric, consistent within Chern-Simons modified gravity; this is true in both the non-dynamical and dynamical frameworks, each of which involves an additional pseudoscalar field coupled to the Pontryagin density. In this paper, we consider stationary first-order perturbations to these metrics in the non-dynamical framework. Under certain assumptions we find analytical solutions to the perturbed field equations. The solutions of the first-order field equations break the translational and cylindrical symmetries of the unperturbed metrics. The effective potential controlling planar geodesic orbits is also affected by the perturbation parameter, which changes the equilibrium radii for the orbits of both massive particles and massless photons.

scholarly journals A new class of analytical solutions describing anisotropic neutron stars in general relativity

2021 ◽  
pp. 2150091
Author(s):  
Jay Solanki ◽  
Bhashin Thakore
Keyword(s):  
General Relativity ◽  
Neutron Stars ◽  
Analytical Solutions ◽  
Radial Pressure ◽  
Compact Stars ◽  
Theory Of Relativity ◽  
Field Equations ◽  
Inherent Anisotropy ◽  
Anisotropic Matter ◽  
New Class

A new class of solutions describing analytical solutions for compact stellar structures has been developed within the tenets of General Relativity. Considering the inherent anisotropy in compact stars, a stable and causal model for realistic anisotropic neutron stars was obtained using the general theory of relativity. Assuming a physically acceptable nonsingular form of one metric potential and radial pressure containing the curvature parameter [Formula: see text], the constant [Formula: see text] and the radius [Formula: see text], analytical solutions to Einstein’s field equations for anisotropic matter distribution were obtained. Taking the value of [Formula: see text] as −0.44, it was found that the proposed model obeys all necessary physical conditions, and it is potentially stable and realistic. The model also exhibits a linear equation of state, which can be applied to describe compact stars.

scholarly journals Anisotropic strange star with Tolman V potential

2018 ◽  
Vol 27 (08) ◽  
pp. 1850089 ◽  
Author(s):  
Dibyendu Shee ◽  
Debabrata Deb ◽  
Shounak Ghosh ◽  
Saibal Ray ◽  
B. K. Guha
Keyword(s):  
Stellar System ◽  
Energy Condition ◽  
Anisotropy Parameter ◽  
Stellar Model ◽  
Compact Stars ◽  
Anisotropic Fluid ◽  
Physical Parameters ◽  
Model Matching ◽  
Field Equations ◽  
Bag Constant

In this paper, we present a strange stellar model using Tolman [Formula: see text]-type metric potential employing simplest form of the MIT bag equation of state (EOS) for the quark matter. We consider that the stellar system is spherically symmetric, compact and made of an anisotropic fluid. Choosing different values of [Formula: see text] we obtain exact solutions of the Einstein field equations and finally conclude that for a specific value of the parameter [Formula: see text], we find physically acceptable features of the stellar object. Further, we conduct different physical tests, viz., the energy condition, generalized Tolman–Oppeheimer–Volkoff (TOV) equation, Herrera’s cracking concept, etc., to confirm the physical validity of the presented model. Matching conditions provide expressions for different constants whereas maximization of the anisotropy parameter provides bag constant. By using the observed data of several compact stars, we derive exact values of some of the physical parameters and exhibit their features in tabular form. It is to note that our predicted value of the bag constant satisfies the report of CERN-SPS and RHIC.

scholarly journals ISOTROPIC CASES OF STATIC CHARGED FLUID SPHERES IN GENERAL RELATIVITY

2011 ◽  
Vol 20 (09) ◽  
pp. 1675-1687 ◽  
Author(s):  
BASANTI DAS ◽  
PRATAP CHANDRA RAY ◽  
IRINA RADINSCHI ◽  
FAROOK RAHAMAN ◽  
SAIBAL RAY
Keyword(s):  
General Relativity ◽  
Analytical Solutions ◽  
Density Ratio ◽  
Compact Stars ◽  
Maxwell Field ◽  
Field Equations ◽  
Charged Fluid ◽  
Isotropic Coordinates ◽  
Charged Fluid Sphere ◽  
Fluid Spheres

In this paper we study the isotropic cases of static charged fluid spheres in general relativity. For this purpose we consider two different specializations and under these we solve the Einstein–Maxwell field equations in isotropic coordinates. The analytical solutions thus obtained are matched to the exterior Reissner–Nordström solutions which concern the values for the metric coefficients eν and eμ. We derive the pressure, density and pressure-to-density ratio at the center of the charged fluid sphere and boundary R of the star. Our conclusion is that static charged fluid spheres provide a good connection to compact stars.

scholarly journals Realistic stellar anisotropic model satisfying Karmarker condition in f(R, T) gravity

2020 ◽  
Vol 80 (1) ◽  
Author(s):  
G. Mustafa ◽  
M. Zubair ◽  
Saira Waheed ◽  
Xia Tiecheng
Keyword(s):  
Observational Data ◽  
Modified Gravity ◽  
Compact Object ◽  
Compact Stars ◽  
Anisotropic Fluid ◽  
Physical Parameters ◽  
Anisotropic Model ◽  
Potential Component ◽  
The Masses ◽  
Object Models

AbstractThe present study explores the $$f(\mathcal {R},\mathcal {T})$$f(R,T) modified gravity on the basis of observational data for three different compact stars with matter profile as anisotropic fluid without electric charge. In this respect, we adopt the well-known Karmarker condition and assume a specific and interesting model for $$\mathrm {g}_{rr}$$grr metric potential component which is compatible with this condition. This choice further leads to a viable form of metric component $$\mathrm {g}_{tt}$$gtt by utilizing the Karmarkar condition. We also present the interior geometry in the reference of Schwarzschild interior and Kohler–Chao cosmological like solutions for $$f(\mathcal {R},\mathcal {T})$$f(R,T) theory. Moreover, we calculate the spacetime constants by using the masses and radii from the observational data of three different compact stars namely 4U 1538-52, LMC X-4 and PSR J1614-2230. In order to explore the viability and stability of the obtained solutions, some physical parameters and properties are presented graphically for all three different compact object models. It is noticed that the parameters c and $$\lambda $$λ have some important and considerable role for these solutions. It is concluded that our obtained solutions are physically acceptable, bearing a well-behave nature in $$f(\mathcal {R},\mathcal {T})$$f(R,T) modified gravity.

scholarly journals A new solution of embedding class I representing anisotropic fluid sphere in general relativity

2016 ◽  
Vol 25 (14) ◽  
pp. 1650099 ◽  
Author(s):  
Ksh. Newton Singh ◽  
Piyali Bhar ◽  
Neeraj Pant
Keyword(s):  
Graphical Representation ◽  
Compact Objects ◽  
Compact Stars ◽  
Anisotropic Fluid ◽  
Physical Parameters ◽  
Satisfactory Description ◽  
Anisotropic Fluid Sphere ◽  
Acceptable Model ◽  
Anisotropic Star ◽  
New Formula

In this paper, we are willing to develop a model of an anisotropic star by choosing a new [Formula: see text] metric potential. All the physical parameters like the matter density, radial and transverse pressure are regular inside the anisotropic star, with the speed of sound less than the speed of light. So the new solution obtained by us gives satisfactory description of realistic astrophysical compact stars. The model of this paper is compatible with observational data of compact objects like RX J1856-37, Her X-1, Vela X-12 and Cen X-3. A particular model of Her X-1 (Mass 0.98 [Formula: see text] and radius[Formula: see text]=[Formula: see text]6.7 km.) is studied in detail and found that it satisfies all the condition needed for physically acceptable model. Our model is described analytically as well as with the help of graphical representation.

Conformally non-flat spacetime representing dense compact objects

2017 ◽  
Vol 32 (18) ◽  
pp. 1750093 ◽  
Author(s):  
Ksh. Newton Singh ◽  
Piyali Bhar ◽  
Farook Rahaman ◽  
Neeraj Pant ◽  
Mansur Rahaman
Keyword(s):  
Static Stability ◽  
Gravitational Theory ◽  
Compact Objects ◽  
Compact Stars ◽  
Relativistic Astrophysics ◽  
Necessary Condition ◽  
Physical Parameters ◽  
University Of Chicago ◽  
Field Equations ◽  
University Of Chicago Press

A new conformally non-flat interior spacetime embedded in five-dimensional (5D) pseudo Euclidean space is explored in this paper. We proceed our calculation with the assumption of spherically symmetric anisotropic matter distribution and Karmarkar condition (necessary condition for class one). This solution is free from geometrical singularity and well-behaved in all respects. We ansatz a new type of metric potential [Formula: see text] and solve for the metric potential [Formula: see text] via Karmarkar condition. Further, all the physical parameters are determined from Einstein’s field equations using the two metric potentials. All the constants of integration are determined using boundary conditions. Due to its conformally non-flat character, it can represent bounded configurations. Therefore, we have used it to model two compact stars Vela X-1 and Cyg X-2. Indeed, the obtained masses and radii of these two objects from our solution are well matched with those observed values given in [T. Gangopadhyay et al., Mon. Not. R. Astron. Soc. 431, 3216 (2013)] and [J. Casares et al., Mon. Not. R. Astron. Soc. 401, 2517 (2010)]. The equilibrium of the models is investigated from generalized TOV-equation. We have adopted [L. Herrera’s, Phys. Lett. A 165, 206 (1992)] method and static stability criterion of Harisson–Zeldovich–Novikov [B. K. Harrison et al., Gravitational Theory and Gravitational Collapse (University of Chicago Press, 1965); Ya. B. Zeldovich and I. D. Novikov, Relativistic Astrophysics, Vol. 1, Stars and Relativity (University of Chicago Press, 1971)] to analyze the stability of the models.

Dissipative planar gravitational collapse in f(G) gravity

2014 ◽  
Vol 29 (13) ◽  
pp. 1450068 ◽  
Author(s):  
M. Sharif ◽  
Ayesha Ikram
Keyword(s):  
Gravitational Collapse ◽  
Gravitational Force ◽  
Field Equations ◽  
Density Inhomogeneity ◽  
Isotropic Source ◽  
Plane Symmetric ◽  
Energy Density Inhomogeneity ◽  
The Impact ◽  
The Relationship ◽  
Physical Quantities

This paper is devoted to analyze the dynamics of plane symmetric gravitational collapse as well as energy density inhomogeneity in f(G) gravity. The field equations are constructed for dissipative isotropic source and Darmois junction conditions are used to discuss the process of collapse. We use Misner–Sharp mechanism to develop dynamical equation and couple it with transport equation to explore the impact of gravitational force on the collapsing rate. For constant f(G) model, we conclude that the rate of collapse slows down. Finally, we discuss the relationship between the Weyl tensor and physical quantities.

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