Showing papers by "Neeraj Pant published in 2021"

Hybrid Charged Stellar Model Via Embedding and Gravitational Decoupling

Abstract: In this paper, we present a new exact anisotropic charged version of Pant’s interior solution [Astrophys. Space Sci. 331, 633 (2011)] by employing the embedding class I condition and the gravitational decoupling via minimal geometric decoupling (MGD) approach. We successfully integrate the coupled Einstein–Maxwell field equations within the MGD and generate a family of new charged anisotropic solutions describing compact stellar objects. The matching of the interior to the exterior Reissner–Nordstrom solution help fix the arbitrary constants. For a chosen parameter space we subject our model to rigorous tests in order to validate its physical viability as a realistic self-gravitating, compact object. We show that the deformation parameter $$\sigma$$ is intrinsically connected to key features such as compactness, mass-to-radius ratio and surface redshift for compact star candidates such as Her X-1, EXO 1785-248, PSR J1614-2230 and SAX J1808.4-3658.

A new parametric class of solutions of a charged anisotropic compact star via Bardeen exterior geometry

Abstract: In this paper, we provide a new parametric class of solutions to Einstein–Maxwell field equations to study the relativistic structure of a compact star via embedding class I condition. The interior...

Three-layered relativistic hybrid star with distinct equation of states

Abstract: In this paper, we are proposing a three-layered hybrid compact star model with a distinct equation of states (EOSs) in the realm of general relativity. The core is assumed to be quark matter described by the MIT-bag model, an intermediate layer filled with neutron liquid and a thin envelope of matter satisfying a quadratic EoS. Three pairs of interfaces are matched by using Darmois–Israel conditions. For better and easier tuning, we have chosen $$\alpha $$ as a free parameter for core, k for intermediate layer and g and t for envelope, while the rest of the constant parameters are linked with mass and radius. Most of the physical parameters such as density, pressures and EoS parameters are continuous in all the three regions; however, $$v_t^2$$ and stability factor are discontinuous. This is because of the non-differentiability of $$p_t$$ ’s at the interfaces. Hence, stability is not defined at the interfaces. Further, matching of $$p_t$$ ’s can be performed by tuning suitable values of the free parameters $$\alpha , ~k, ~g$$ and t. Further, the most prevailing aspect of this method is that we can arbitrarily choose the radii of each region. As per Buchler and Barkat (PRL 27: 48, 1971) and Baym et al.(PRL 175: 225, 1971) , there exists a smooth transition density between quark core and intermediate neutron-liquid layer at about $$\rho > 10^{14}~{\mathrm{g/cc}}$$ . Our calculation shows that the smooth transition density is at about $$\rho _I=4.16 \times 10^{14}~ {\mathrm{g/cc}}$$ which is in good agreement with the above prediction.

A new class of viable and exact solutions of EFE's with Karmarkar conditions: An application to cold star modeling

Abstract: In this work we present a theoretical framework within Einstein's classical general relativity which models stellar compact objects such as PSR J1614-2230 and SAX J1808.4-3658. The Einstein field equations are solved by assuming that the interior of the compact object is described by a class I spacetime. The so-called Karmarkar condition arising from this requirement is integrated to reduce the gravitational behaviour to a single generating function. By appealing to physics we adopt a form for the gravitational potential which is sufficiently robust to accurately describe compact objects. Our model satisfies all the requirements for physically realistic stellar structures.

Relativistic anisotropic models of ultra-dense stellar objects under embedding class I

Abstract: In this paper, we present a new class of exact solutions satisfying Einstein’s field and modified TOV-equations. The thermodynamic quantities of stellar matter like anisotropic pressures, baryon density, red-shift and velocity of sound have been investigated using the embedding class I methodology with the Karmarkar condition. The solutions satisfy the static stability criterion, energy conditions, stability factor, adiabatic index and causality condition. In addition to it, we perform complete graphical analysis of neutron stars in Vela $$X-1$$ and Her $$X-1$$ in the setting of the Karmarkar space-time.

Relativistic compact stars in the Kuchowicz space-time

Abstract: We present an anisotropic charged analogue of Kuchowicz (1971) solution of the general relativistic field equations in curvature coordinates by using simple form of electric intensity E and pressure anisotropy factor $$\Delta $$ that involve charge parameter K and anisotropy parameter $$\alpha $$ , respectively. Our solution is well behaved in all respects for all values of X (X is related to the radius of the star) lying in the range $$0< X \le 0.6$$ , $$\alpha $$ lying in the range $$0 \le \alpha \le 1.3$$ , K lying in the range $$0< K \le 1.75$$ and Schwarzschild compactness parameter “u” lying in the range $$0< u \le 0.338$$ . Since our solution is well behaved for a wide range of the parameters, we can model many different types of ultra-cold compact stars like quark stars and neutron stars. We present some models of super-dense quark stars and neutron stars corresponding to $$X=0.2,~\alpha =0.2$$ and $$K=0.5$$ for which $$u_{\max }=0.15$$ . By assuming surface density $$\rho _b=4.6888\times 10^{14}~ g/cc$$ , the mass and radius are $$0.955 M_\odot $$ and 9.439km, respectively. For $$\rho _b=2.7\times 10^{14}~ g/cc$$ , the mass and radius are $$1.259 M_\odot $$ and 12.439km, respectively, and for $$\rho _b=2\times 10^{14}~ g/cc$$ , the mass and radius are $$1.463 M_\odot $$ and 14.453km, respectively. It is also shown that inclusion of more electric charge and anisotropy enhances the static stable configuration under radial perturbations. The $$M-R$$ graph suggests that the maximum mass of the configuration depends on the surface density, i.e., with the increase in surface density, the maximum mass and corresponding radius decrease. This may be because of existence of exotic matters at higher densities that soften the EoSs.

Modified Chaplygin gas in anisotropic universes on the brane

Abstract: In this paper, we study anisotropic universes with Modified Chaplygin gas (MCG) in the context of Randall Sundrum-2 (RS2) braneworld model. The cosmological solutions for Kantowski–Sachs (KS) and B...