Conformally flat polytropes for anisotropic cylindrical geometry

2015 ◽  
Vol 93 (12) ◽  
pp. 1583-1587 ◽  
Author(s):  
M. Sharif ◽  
Sobia Sadiq
Keyword(s):  
Gravitational Potential ◽  
Equations Of State ◽  
Graphical Analysis ◽  
Cylindrical Geometry ◽  
Energy Conditions ◽  
Conformally Flat ◽  
Matter Distribution ◽  
Anisotropic Matter ◽  
Cylindrically Symmetric ◽  
Flat Condition

In this paper, we study cylindrically symmetric anisotropic matter distribution satisfying two polytropic equations of state. The corresponding Lane–Emden equations are constructed and the energy conditions are checked. We evaluate a particular expression for anisotropy by using the conformally flat condition, which helps in the study of polytropic models. The graphical analysis of surface gravitational potential indicates the increasing behavior of model compactness. Finally, we conclude that one of the obtained models is physically viable.

Effects of charge on anisotropic conformally flat polytropes

2015 ◽  
Vol 93 (11) ◽  
pp. 1420-1426 ◽  
Author(s):  
M. Sharif ◽  
Sobia Sadiq
Keyword(s):  
Electromagnetic Field ◽  
Equations Of State ◽  
Compact Object ◽  
Spherically Symmetric ◽  
Conformally Flat ◽  
Matter Distribution ◽  
Anisotropic Matter ◽  
Flat Condition

In this paper, we study the effects of electromagnetic field on conformally flat spherically symmetric anisotropic matter distribution satisfying two polytropic equations of state. We consider conformally flat condition and evaluate corresponding anisotropy, which is used to study polytropes for the charged compact object. Finally, we study stability of the resulting models using the Tolman mass. It is concluded that only one of the resulting models is physically viable.

Study of tilted anisotropic polytropes

2019 ◽  
Vol 28 (03) ◽  
pp. 1950051
Author(s):  
M. Sharif ◽  
Sobia Sadiq
Keyword(s):  
Equations Of State ◽  
Conservation Equation ◽  
Specific Form ◽  
Energy Conditions ◽  
Spherically Symmetric ◽  
Conformally Flat ◽  
Anisotropic Matter ◽  
Conformal Flatness ◽  
Energy Bound ◽  
Aids Study

The purpose of this paper is to construct spherically symmetric models for anisotropic matter configurations by imposing conformally flat conditions. This work is done for a relatively moving observer with matter using two types of polytropic equations of state. We evaluate the corresponding conservation equation, mass equation as well as energy constraints for both choices of equations of state. The conformal flatness is employed to find a specific form of anisotropy which aids study to spherical polytropic configurations. It is found that the first model satisfies all the energy conditions while the second model does not meet the dominant energy bound. It is also found that both models remain stable throughout the evolution.

Study of conformally flat polytropes with tilted congruence

2018 ◽  
Vol 27 (07) ◽  
pp. 1850063 ◽  
Author(s):  
M. Sharif ◽  
Sobia Sadiq
Keyword(s):  
Equation Of State ◽  
Matter Content ◽  
Energy Conditions ◽  
Spherically Symmetric ◽  
Conformally Flat ◽  
Flat Condition ◽  
Polytropic Equation ◽  
Dissipative Fluid ◽  
Symmetric Spacetime ◽  
Fluid Configuration

This paper is aimed to study the modeling of spherically symmetric spacetime in the presence of anisotropic dissipative fluid configuration. This is accomplished for an observer moving relative to matter content using two cases of polytropic equation-of-state under conformally flat condition. We formulate the corresponding generalized Tolman–Oppenheimer–Volkoff equation, mass equation, as well as energy conditions for both cases. The conformally flat condition is imposed to find an expression for anisotropy which helps to study spherically symmetric polytropes. Finally, Tolman mass is used to analyze stability of the resulting models.

scholarly journals Bouncing Cosmology in f G , T Gravity with Logarithmic Trace Term

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
M. Farasat Shamir
Keyword(s):  
Equations Of State ◽  
Graphical Analysis ◽  
Conservation Equation ◽  
Energy Conditions ◽  
Accelerating Universe ◽  
Shift Function ◽  
Constraint Equations ◽  
Bouncing Cosmology ◽  
Strong Energy ◽  
Free Parameters

This study is devoted to explore bouncing cosmology in the context of f G , T theory of gravity. For this purpose, a Gauss–Bonnet cosmological model with logarithmic trace term is considered. In particular, the possibility of obtaining bouncing solutions by considering two equations of state parameters is investigated. A graphical analysis is provided for analyzing the obtained bouncing solutions. The energy conditions are discussed in detail. It is interesting to notice that null and strong energy conditions are violated near the neighborhood of bouncing points justifying the accelerating universe in the light of the recent observational data. The behavior of the scale factor, red shift function, deceleration parameter, and Hubble parameter is also debated. An important feature of the current study is the discussion of conservation equation in f G , T gravity. The possibility of some suitable constraint equations which recover the standard conservation equation is discussed, and all the free parameters are assumed accordingly. All the results in this study suggest that the proposed f G , T gravity model provides good bouncing solutions with the chosen EoS parameters.

scholarly journals Some specific wormhole solutions in f(R)-modified gravity theory

2021 ◽  
pp. 2150024
Author(s):  
Bikram Ghosh ◽  
Saugata Mitra ◽  
Subenoy Chakraborty
Keyword(s):  
Modified Gravity ◽  
Shape Function ◽  
Matter Field ◽  
Gravity Theory ◽  
Energy Conditions ◽  
Spherically Symmetric ◽  
Shape Functions ◽  
Matter Distribution ◽  
Anisotropic Matter ◽  
Modified Gravity Theory

The paper deals with the static spherically symmetric wormhole solutions in [Formula: see text]-modified gravity theory with anisotropic matter field and for some particular choices for the shape functions. This work may be considered as an extension of the general formalism in [S. Halder, S. Bhattacharya and S. Chakraborty, Phys. Lett. B 791, 270 (2019)] for finding wormhole solutions. For isotropic matter distribution it has been shown that wormhole solutions are possible for zero tidal force and it modifies the claim in [M. Cataldo, L. Leimpi and P. Rodriguez, Phys. Lett. B 757, 130 (2016)]. Finally, energy conditions are examined and it is found that all energy conditions are satisfied in a particular domain with a particular choice of the shape function.

Quintessence compact stars with Vaidya–Tikekar type grr for anisotropic fluid

2020 ◽  
Vol 98 (9) ◽  
pp. 869-876
Author(s):  
G. Abbas ◽  
M.R. Shahzad
Keyword(s):  
Killing Vector ◽  
Graphical Analysis ◽  
Compact Stars ◽  
Energy Conditions ◽  
Anisotropic Fluid ◽  
Conformal Killing ◽  
Field Equations ◽  
Anisotropic Matter ◽  
Quintessence Field ◽  
Analytical Expressions

The present study provides a new solution to the Einstein field equations for anisotropic matter configuration in static and spherically symmetric space–time. By taking benefit from the conformal Killing vector (CKV) technique and quintessence field specified by a parameter ωq as –1 < ωq < –1/3, we generate an exact solution to the field equations. For this investigation, we have used a specific form of metric potential taken fromVaidya–Tikekar (J. Astrophys. Astron. 3, 325 (1982)) geometry. To canvass the physical plausibility of the presented solution, we explored some analytical expressions such as energy conditions, the TOV equation, stability analysis, and equation of state parameters. We present graphical analysis of the necessary analytical expressions that revealed that our solution satisfies the necessary physical conditions.

Stellar shear-free gravitational collapse with Karmarkar condition in f(R) gravity

2019 ◽  
Vol 34 (33) ◽  
pp. 1950220 ◽  
Author(s):  
G. Abbas ◽  
H. Nazar
Keyword(s):  
Gravitational Collapse ◽  
Graphical Analysis ◽  
Energy Conditions ◽  
Heat Conducting ◽  
Star Model ◽  
Matter Distribution ◽  
Interior Space ◽  
Alternative Formula ◽  
Vaidya Solution ◽  
Distribution Energy

This work has investigated the outcomes of spherically symmetric radiating dissipative gravitational collapse model with anisotropic heat conducting matter distribution by imposing time-dependent Karmarkar condition in the alternative [Formula: see text] theory of gravity. For this evaluation, we defined the smooth matching conditions between the interior space–time and exterior Vaidya solution at the junction interface. Afterwards, we have found an exact particular solution of our radiative star model by using the Karmarkar condition. Moreover, the physical components of the matter distribution, energy conditions and time relaxational effects on the temporal profile are thoroughly discussed with graphical analysis which indicates the system is well behaved.

scholarly journals Cylindrically Symmetric, Asymptotically Flat, Petrov Type D Spacetime with a Naked Curvature Singularity and Matter Collapse

2017 ◽  
Vol 2017 ◽  
pp. 1-6 ◽  
Author(s):  
Faizuddin Ahmed
Keyword(s):  
Cosmic Time ◽  
Petrov Type ◽  
Energy Conditions ◽  
Anisotropic Fluid ◽  
Curvature Singularity ◽  
Field Equations ◽  
Asymptotically Flat ◽  
Type D ◽  
Cylindrically Symmetric ◽  
Petrov Type D

We present a cylindrically symmetric, Petrov type D, nonexpanding, shear-free, and vorticity-free solution of Einstein’s field equations. The spacetime is asymptotically flat radially and regular everywhere except on the symmetry axis where it possesses a naked curvature singularity. The energy-momentum tensor of the spacetime is that for an anisotropic fluid which satisfies the different energy conditions. This spacetime is used to generate a rotating spacetime which admits closed timelike curves and may represent a Cosmic Time Machine.

scholarly journals KINKS, ENERGY CONDITIONS AND CLOSED TIMELIKE CURVES

2000 ◽  
Vol 09 (05) ◽  
pp. 531-541 ◽  
Author(s):  
PEDRO F. GONZÁLEZ-DÍAZ
Keyword(s):  
Energy Condition ◽  
Weak Energy Condition ◽  
Energy Conditions ◽  
Closed Timelike Curves ◽  
Causality Violation ◽  
Incoherent Radiation ◽  
Cylindrically Symmetric ◽  
Cylindrically Symmetric Spacetime ◽  
Geodesically Complete ◽  
Symmetric Spacetime

A link between the possibility of extending a geodesically incomplete kinked spacetime to a spacetime which is geodesically complete and the energy conditions is discussed for the case of a cylindrically-symmetric spacetime kink. It is concluded that neither the strong nor the weak energy condition can be satisfied in the four-dimensional example, though the latter condition may survive on the transversal sections of such a spacetime. It is also shown that the matter which propagates quantum-mechanically in a kinked spacetime can always be trapped by closed timelike curves, but signaling connections between that matter and any possible observer can only be made of totally incoherent radiation, so preventing observation of causality violation.

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