RELATIVISTIC SUPERDENSE STAR MODELS OF PSEUDO SPHEROIDAL SPACE–TIME

2005 ◽  
Vol 14 (06) ◽  
pp. 1037-1048 ◽  
Author(s):  
RAMESH TIKEKAR ◽  
KANTI JOTANIA
Keyword(s):  
Space Time ◽  
Compact Stars ◽  
Field Equations ◽  
Relativistic Field ◽  
Interior Space ◽  
Strange Matter ◽  
Superdense Stars ◽  
Star Models ◽  
Superdense Star ◽  
Spheroidal Geometry

The physically viable models of compact stars like SAX (J1808.4-3658) can be obtained using Vaidya–Tikekar ansatz prescribing spheroidal geometry for their interior space–time. We discuss here the suitability of an alternative ansatz in this context. The models of superdense star are proposed using a general three parameter family of solutions of relativistic field equations obtained adopting the alternative ansatz. The setup is shown to admit physically viable models of superdense stars and strange matter stars such as Her. X-1.

NON-ADIABATIC GRAVITATIONAL COLLAPSE OF A SUPERDENSE STAR

2010 ◽  
Vol 19 (12) ◽  
pp. 1889-1904 ◽  
Author(s):  
SANJAY SARWE ◽  
RAMESH TIKEKAR
Keyword(s):  
Black Hole ◽  
Heat Flow ◽  
Gravitational Collapse ◽  
Adiabatic Shear ◽  
Dissipative Forces ◽  
Superdense Stars ◽  
Superdense Star ◽  
Radiating Star ◽  
Spheroidal Geometry ◽  
Relativistic Equations

The relativistic equations governing the non-adiabatic shear-free collapse of massive superdense stars in the presence of dissipative forces producing heat flow in the background of space–times of the Vaidya–Tikekar ansatz with associated physical three-spaces that have the three-spheroidal geometry are formulated. It is shown how the system can be used to examine the development and progress of the collapse during subsequent epochs until the radiating star becomes a black hole.

PARABOLOIDAL SPACE–TIMES AND RELATIVISTIC MODELS OF STRANGE STARS

2006 ◽  
Vol 15 (08) ◽  
pp. 1175-1182 ◽  
Author(s):  
KANTI JOTANIA ◽  
RAMESH TIKEKAR
Keyword(s):  
Space Time ◽  
Interior Space ◽  
Strange Stars ◽  
X Ray ◽  
Superdense Stars ◽  
Relativistic Models

The objective of this paper is to find out the suitability of an ansatz similar to that suggested by Vaidya–Tikekar, but prescribing paraboloidal geometry for the 3-space of the interior space–time of a relativistic spherical star in describing a family of physically viable models of superdense stars like Her X-1, SAX, and X-ray brust.

scholarly journals Relativistic strange stars with anisotropy and B-parameter in pseudo spheroidal space time

2012 ◽  
Vol 8 (S291) ◽  
pp. 362-364
Author(s):  
P. K. Chattopadhyay ◽  
B. C. Paul
Keyword(s):  
Equation Of State ◽  
Compact Star ◽  
Anisotropy Parameter ◽  
Space Time ◽  
Stable Model ◽  
Strange Stars ◽  
Strange Matter ◽  
Pressure Anisotropy ◽  
Spheroidal Geometry ◽  
Anisotropic Case

AbstractA class of compact cold stars in the presence of strange matter is obtained for a pseudo-spheroidal geometry. Considering the strange matter equation of state $p = \frac{1}{3}(\rho-4B)$ with pressure anisotropy described by Vaidya-Tikekar metric, we determine the parameter B both inside and on the surface of the star for different values of anisotropy parameter α. In the anisotropic case, we note that a stable model of a compact star may be realized.

scholarly journals Exact solutions for compact stars with CFL quark matter

2020 ◽  
Vol 29 (07) ◽  
pp. 2050044 ◽  
Author(s):  
L. S. Rocha ◽  
A. Bernardo ◽  
M. G. B. De Avellar ◽  
J. E. Horvath
Keyword(s):  
Exact Solutions ◽  
Quark Matter ◽  
Dense Matter ◽  
Compact Stars ◽  
Einstein Field Equations ◽  
Field Equations ◽  
Strange Matter ◽  
Mit Bag Model ◽  
Wide Range ◽  
The One

The search for the true ground state of the dense matter remains open since Bodmer, Terazawa and others raised the possibility of stable quark matter, boosted by Witten’s strange matter hypothesis in 1984. Within this proposal, the strange matter is assumed to be composed of [Formula: see text] quarks in addition to the usual [Formula: see text]s and [Formula: see text]s, having an energy per baryon lower than the strangeless counterpart, and even lower than that of nuclear matter. In this sense, neutron stars should actually be strange stars. Later work showed that a paired, symmetric in flavor, color-flavor locked (CFL) state would be preferred to the one without any pairing for a wide range of the parameters (gap [Formula: see text], strange quark mass [Formula: see text] and bag constant B). We use an approximate, yet very accurate, CFL equation-of-state (EoS) that generalizes the MIT bag model to obtain two families of exact solutions for the static Einstein Field Equations (EFE) constructing families of anisotropic compact relativistic objects. In this fashion, we provide exact useful solutions directly connected with microphysics.

Analysis of physically realizable stellar models in embedded class one spacetime manifold

2019 ◽  
Vol 35 (04) ◽  
pp. 2050001 ◽  
Author(s):  
Ritu Tamta ◽  
Pratibha Fuloria
Keyword(s):  
Transverse Velocity ◽  
Compact Star ◽  
Graphical Analysis ◽  
Compact Stars ◽  
Field Equations ◽  
Star Models ◽  
New Exact Solutions ◽  
Spacetime Manifold ◽  
Stellar Models ◽  
The Stability

In this paper, we searched two new exact solutions of Einstein’s field equations for modeling of compact cold stars using embedded class one spacetime continuum. We find out the expressions for pressure, density, anisotropy, redshift, metric potentials and other physical variables in terms of algebraic and trigonometric expressions and observe that all variables show well-behaved trends inside the compact stellar configurations. The causality condition is well maintained by our stellar models, i.e. the radial velocity and transverse velocity are less than l. The stability of our models is assessed via different stability criteria. The Buchdahl condition holds good for our solution. Herrera’s cracking method is applied to check the stability of stellar models. We generate anisotropic compact star models, whose masses and radii are in close agreement with the observed values for compact stars 4U 1538-52, LMCX-4, PSRJ1614-2230. A comparative analysis of the proposed models is carried out based on two different solutions reported in the paper. The appropriate graphical analysis is provided to authenticate the viability of the models.

scholarly journals Anisotropic compact stars via embedding approach in general relativity: new physical insights of stellar configurations

2021 ◽  
Vol 81 (3) ◽  
Author(s):  
Abdelghani Errehymy ◽  
Youssef Khedif ◽  
Mohammed Daoud
Keyword(s):  
General Relativity ◽  
Space Time ◽  
Compact Stars ◽  
Energy Conditions ◽  
Spherically Symmetric ◽  
Interior Space ◽  
Exterior Space ◽  
New Family ◽  
Embedding Class One ◽  
Physical Tests

AbstractThe main focus of this paper is to explore the possibility of providing a new family of exact solutions for suitable anisotropic spherically symmetric systems in the realm of general relativity involving the embedding spherically symmetric static metric into the five-dimensional pseudo-Euclidean space. In this regard, we ansatz a new metric potential $$\lambda (r)$$ λ ( r ) , and we obtained the other metric potential $$\nu (r)$$ ν ( r ) by mains of embedding class one approach. The unknown constants are determined by the matching of interior space-time with the Schwarzschild exterior space-time. The physical acceptability of the generating celestial model for anisotropic compact stars is approved via acting several physical tests of the main salient features viz., energy density, radial and tangential pressures, anisotropy effect, dynamical equilibrium, energy conditions, and dynamical stability, which are well-compared with experimental statistics of four different compact stars: PSR J1416-2230, PSR J1903+327, 4U 1820-30 and Cen X-3. Conclusively, all the compact stars under observations are realistic, stable, and are free from any physical or geometrical singularities. We find that the embedding class one solution for anisotropic compact stars is viable and stable, plus, it provides circumstantial evidence in favor of super-massive pulsars.

scholarly journals Minimally deformed anisotropic stars by gravitational decoupling in Einstein–Gauss–Bonnet gravity

2021 ◽  
Vol 81 (9) ◽  
Author(s):  
S. K. Maurya ◽  
Anirudh Pradhan ◽  
Francisco Tello-Ortiz ◽  
Ayan Banerjee ◽  
Riju Nag
Keyword(s):  
Einstein Gravity ◽  
Space Time ◽  
Compact Stars ◽  
Interior Solution ◽  
Interior Space ◽  
Bonnet Gravity ◽  
Geometric Deformation ◽  
Anisotropic Stars ◽  
Interior Solutions ◽  
Deformation Approach

AbstractIn this article, we develop a theoretical framework to study compact stars in Einstein gravity with the Gauss–Bonnet (GB) combination of quadratic curvature terms. We mainly analyzed the dependence of the physical properties of these compact stars on the Gauss–Bonnet coupling strength. This work is motivated by the relations that appear in the framework of the minimal geometric deformation approach to gravitational decoupling (MGD-decoupling), we establish an exact anisotropic version of the interior solution in Einstein–Gauss–Bonnet gravity. In fact, we specify a particular form for gravitational potentials in the MGD approach that helps us to determine the decoupling sector completely and ensure regularity in interior space-time. The interior solutions have been (smoothly) joined with the Boulware–Deser exterior solution for 5D space-time. In particular, two different solutions have been reported which comply with the physically acceptable criteria: one is the mimic constraint for the pressure and the other approach is the mimic constraint for density. We present our solution both analytically and graphically in detail.

scholarly journals Model of Charged Anisotropic Strange Stars in Minimally Coupled f R Gravity

2021 ◽  
Vol 2021 ◽  
pp. 1-25
Author(s):  
H. Nazar ◽  
G. Abbas
Keyword(s):  
Energy Density ◽  
Graphical Representation ◽  
Radial Pressure ◽  
Mass Function ◽  
Compact Stars ◽  
Energy Conditions ◽  
Anisotropic Fluid ◽  
Field Equations ◽  
Strange Matter ◽  
New Family

In the present article, we have investigated a new family of nonsingular solutions of static relativistic compact sphere which incorporates the characteristics of anisotropic fluid and electromagnetic field in the context of minimally coupled f R theory of gravity. The strange matter MIT bag model equation of state (EoS) has been considered along with the usual forms of the Karori–Barua KB metric potentials. For this purpose, we derived the Einstein–Maxwell field equations in the assistance of strange matter EoS and KB type ansatz by employing the two viable and cosmologically well-consistent models of f R = R + γ R 2 and f R = R + γ R R + α R 2 . Thereafter, we have checked the physical acceptability of the proposed results such as pressure, energy density, energy conditions, TOV equation, stability conditions, mass function, compactness, and surface redshift by using graphical representation. Moreover, we have investigated that the energy density and radial pressure are nonsingular at the core or free from central singularity and always regular at every interior point of the compact sphere. The numerical values of such parameters along with the surface density, charge to radius ratio, and bag constant are computed for three well-known compact stars such as CS1 SAXJ 1808 . 4 − 3658 ( x ˜ = 7.07   km , CS2 VelaX − 1 x ˜ = 9.56   km , and CS3 4U1820 − 30 x ˜ = 10   km and are presented in Tables 1–6. Conclusively, we have noticed that our presented charged compact stellar object in the background of two well-known f R models obeys all the necessary conditions for the stable equilibrium position and which is also perfectly fit to compose the strange quark star object.

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