arXiv subjects

B. S. Ratanpal

Publications and source records attributed to B. S. Ratanpal.

At least 19 recordsLinked to original sources

arXiv2024

Solution of Einstein Field Equations for Anisotropic Matter with Vanishing Complexity: Spacetime Metric Satisfying Karmarkar Condition and Conformally Flat Geometry

The solution of Einstein field equations for static spherically symmetric spacetime metric with anisotropic internal stresses has been obtained. The matter has vanishing complexity and a spacetime metric that satisfies the Karmarkar condition and is conformally flat. It has been noted that there is only one solution that meets these three conditions. This has been shown as a proof of the theorem.

gr-qc↗

arXiv2024

Anisotropic star with a linear equation of state (EOS)

A family of solutions defining the interior of a static, spherically symmetric, compact anisotropic star is described by considering a new form of the equation of state (EOS). The analytic solution is derived by using the Finch and Skea ansatz for the metric potential g_rr, which has a clear geometric interpretation for the related background spacetime. The model parameters are fixed by smooth matching of the interior solution to the Schwarzschild exterior metric over the bounding surface of the compact star, together with the requirement that the radial pressure vanishes at the boundary. Data available for the pulsar 4U1802030 has been utilized to analyze the physical viability of the developed model. The model is shown to be stable.

gr-qc↗

arXiv2023

A various equation of state for anisotropic models of compact star

We obtain models of compact stars having pressure anisotropy on Finch-Skea spacetime by considering generalized equation of state (EoS), whose particular cases are linear, quadratic, polytropic, chaplygin and colour - flavor locked(CFL) equation of states. The physical viability of models are tested for strange star candidate 4U 1820 - 30 having mass M = 1.58Mass of the sun and radius R = 9.1 km. All the models are physically plausible.

gr-qc↗

arXiv2023

Anisotropic Approach: Compact star as generalized Model

We studied a new class of interior solutions that are singular-free and useful for describing anisotropic compact star objects with spherically symmetric matter distribution. We have considered metric potential selecting B_0^2 (r)=1/(1-r^2/R^2 )^n ,where n>2 . The various physical characteristics of the model are specifically examined for the pulsar PSRJ1903+327 with its current estimated data. According to analysis, every physical need for a physically admissible star is satisfied and all features are acceptable. Further, the stability of the model has been examined. Numerous physical characteristics are also highlighted in a graphical form.

gr-qc↗

arXiv2023

Generalized Finch and Skea model compatible with observational data

We present an entirely new class of solutions to Einstein's field equations that correspond to a static spherically symmetric anisotropic system by generalizing the Finch and Skea ansatz using the linear equation of state for the gravitational potential $g_{rr} $. Based on physical requirements, regularity condition, and stability, we make various assumptions about the model's parameters. The exact solution generates a plausible model of a compact star PSR J0348+0432 that satisfies all physical criteria. The requirements for a well-behaved compact star are met, including regularity, equilibrium, causality, stability, energy, and compactness limitations.

gr-qc↗

arXiv2023

New charged anisotropic solution on paraboloidal spacetime

New exact solutions of Einstein's field equations for charged stellar models by assuming linear equation of state $ P_r=A(ρ-ρ_{a}) $, where $ P_r $ is the radial pressure and $ ρ_{a} $ is the surface density. By assuming $ e^λ = 1+\frac{r^2}{R^2} $ for metric potential. The physical acceptability conditions of the model are investigated, and the model is compatible with several compact star candidates like 4U 1820-30, PSR J1903+327, EXO 1785-248, Vela X-1, PSR J1614-2230, Cen X-3. A noteworthy feature of the model is that it satisfies all the conditions needed for a physically acceptable model.

gr-qc↗

arXiv2022

Anisotropic Compact Star Model on Finch-Skea Spacetime

In this study, we demonstrate a new anisotropic solution to the Einstein field equations in Finch-Skea spacetime. The physical features of stellar configuration are studied in previous investigations. We create a model that meets all physical plausibility conditions for a variety of stars and plot graphs for \textbf{4U 1820-30}.

gr-qc↗

arXiv2022

A new solution of Einstein's field equations in isotropic coordinates

In this work, an exact solution of Einstein's field equations in isotropic coordinates for anisotropic matter distribution is obtained by considering a particular metric choice of metric potential $g_{rr}$. To check the feasibility of the model, we have investigated all the physical characteristics of a realistic star. It is found that the model is potentially stable, and the adiabatic index is greater than $\frac{4}{3}$. The model have been analysed for Compact star \textbf{4U 1538-52}.

gr-qc↗

arXiv2022

Controllability Analysis of Motion of Artificial Satellite Under the Effect of Oblateness of the Earth

In this article we have studied the controllability of artificial satellite under the effect of zonal harmonic $J_2$ in cylindrical polar coordinates systems. Seven different cases of thrusters in various directions have been analyzed and it is found that the system is controllable if we apply thrusters in either $r$, $θ$ and $z$ or $θ$ and $z$ direction. The equations governing motion of satellite have been linearized and Kalman controllability test is applied to check the controllability of the system. We have also derived controller $u$ for the linearized system. The trajectory of the system have been plotted to show the controllability of the system.

math.OC↗

arXiv2020

Compact Relativistic Stars under Karmarkar Condition

A class of new solutions for Einstein's field equations, by choosing the ansatz $e^{λ(r)}=\frac{1+ar^{2}}{1+br^{2}}$ for metric potential, are obtained under Karmarkar condition. It is found that a number of pulsars like 4U 1820-30, PSR J1903+327, 4U 1608-52, Vela X-1, PSR J1614-2230, Cen X-3 can be accomodated in this model. We have displayed the nature of physical parameters and energy conditions throughout the distribution using numerical and graphical methods for a particular pulsar 4U 1820-30 and found that the solution satisfies all physical requirements.

gr-qc↗

arXiv2020

Cracking and Stability of Non-Rotating Relativistic Spheres with Anisotropic Internal Stresses

The stability of static uncharged spheres with anisotropic internal stresses is studied in general relativity. It has been noticed that pressure anisotropy plays an important role for stability of stellar structure. It is shown that radial profile of the stress anisotropy can be considered to decide potentially stable/unstable regions. Finally, pontentially stable/unstable regions of two known models of relativistic star have been examined.

gr-qc↗

arXiv2020

Motion of Satellite under the Effect of Oblateness of Earth and Atmospheric Drag

The equations governing motion of the satellite under the effect of oblateness of Earth and atmospheric drag have been simulated, for a fixed initial position and three different initial velocities, till satellite collapses on Earth. Simulation of motion of artificial Earth satellite subject to the combined effects of oblate Earth and atmospheric drag is presented. The atmospheric model considered here takes in to account of exponential variation of the density with initial distance of Satellite from Earth's surface, scale height and radial distance. The minimum and maximum values of orbital elements and their variation over a time for different initial velocities have been reported.

physics.space-ph↗

arXiv2019

Charged Polytropic Models on Finch-Skea Spacetime

The static, charged, spherically symmetric matter distribution have been studied by considering polytropic equation of state. Two polytropic indices have been considered for study. The plots of density, radial pressure, tangential pressure, anisotropy and causality condition indicates the models are suitable to describe the relativistic polytropes.

gr-qc↗

arXiv2017

Anisotropic stars for spherically symmetric spacetimes satisfying the Karmarkar condition

A new class of solution describing an anisotropic stellar configuration satisfying Karmarkar's condition i.e. spherically symmetric metric of embedding class 1, is reported. It has been shown that the compact star model is physically well-behaved and meet all the physical requirements for a stable configuration in hydrostatic equilibrium. Our model describes compact stars like Vela X-1 and 4U1608-52 to a very good approximation.

gr-qc↗

arXiv2016

A New Class of Anisotropic Charged Compact Star

A new model of charged compact star is reported by solving the Einstein-Maxwell field equations by choosing a suitable form of radial pressure. The model parameters $ρ$, $p_r$, $p_{\perp}$ and $E^{2}$ are in closed form and all are well behaved inside the stellar interior. A comparative study of charged and uncharged model is done with the help of graphical analysis.

gr-qc↗

arXiv2016

Charged compact stellar model in Finch-Skea spacetime

In this paper a compact charged stellar model in the Finch and Skea background spacetime [{\it Class. Quantum Gravity} {\bf6}, 467 (1989)] is presented. The model has been developed by assuming a particular charge distribution within the stellar interior. The model is well behaved and can describe a large class of compact stars. Physical features of the model are studied and in particular we show how the presence of charge can have a non-negligible impact on the mass-radius ($M-R$) relationship of such class of stars.

gr-qc↗

arXiv2016

A New Anisotropic Compact Star Model having Matese \& Whitman Mass Function

A new singularity free model of anisotroipic compact star is proposed. The Einstein field equations are solved in closed form by utilizing Matese \& Whitman mass function. The model parameters $ρ$, $p_r$ and $p_t$ all are well behaved inside the stellar interior and our model satisfies all the required conditions to be physically acceptable. The model given in the present work is compatible with observational data of compact objects like SAX J 1808.4-3658 (SS1), SAX J 1808.4-3658 (SS2) and 4U 1820-30. A particular model of 4U 1820-30 is studied in detail and found that it satisfies all the condition needed for physically acceptable model. The present work is the generalization of Sharma and Ratanpal\cite{sharma13} model for compact stars admitting quadratic equation of state.

gr-qc↗

arXiv2015

Charged Anisotropic Star on Paraboloidal Spacetime

The charged anisotropic star on paraboloidal spacetime is reported by choosing particular form of radial pressure and electric field intensity. The non-singular solution of Einstein-Maxwell system of equation have been derived and it is shown that model satisfy all the physical plausibility conditions. It is observed that in the absence of electric field intensity, model reduces to particular case of uncharged Sharma \& Ratanpal model. It is also observed that the parameter used in electric field intensity directly effects the mass of the star.

gr-qc↗