General relativistic polytropes in anisotropic stars

Isayev, A. A.

doi:10.1103/physrevd.96.083007

Cited by 38 publications

(24 citation statements)

References 53 publications

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“…Of course, stability can be considered from different approaches and stability with respect to one type of perturbation does not imply stability with respect to another perturbation. In particular with respect to radial oscillations the system may not be stable and this may be developed in future investigations [47]. Even though in each case the proposed value for the compacity does not change because it does not depend of the parameter n associated with the anisotropy, the density, pressures and speeds of sound if those have a certain dependency on the value of n. The Fig.…”

Section: Compact Starsmentioning

confidence: 99%

On the effect of anisotropy on stellar models

Estevez-Delgado

2018

Eur. Phys. J. C

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The relevance of anisotropy in compact models is shown by the construction of a stellar model, this can influence the behavior of density, pressure and speed of sound in such grade that if the anisotropy disappear it could produce a regular model of perfect fluid which is not physically acceptable. The present anisotropic model has dependence in two parameters n associated with the anisotropy and w related with the rate of compactness u = G M/c 2 R, this is regular and physically acceptable. That is the speed of sound is positive and lower than the light speed, the density as well as radial and tangential pressure are monotonic decrescent functions. The compactness values for which the radial and tangential speed of sound are monotonic decrescent functions and the solution is potentially stable occurs for u ≤ 0.2073450586, and in particular for the maximum value of u n ∈ [−0.771108398, −0.231572621]. While if n = 1 we get a model of perfect regular fluid but the density and speed of sound can not be both positive at the origin, so the solution is not physically acceptable in the absence of anisotropic pressures.

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Section: Compact Starsmentioning

confidence: 99%

On the effect of anisotropy on stellar models

Estevez-Delgado

2018

Eur. Phys. J. C

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“…In the following Section we will consider some EoS widely used in literature [23][24][25][26] in order to describe the anisotropic inner fluid distribution of compact objects. In this way we will determine which one is the most suitable for fitting the profiles of the above thermodynamical quantities.…”

Section: A Viable Interior Solutionmentioning

confidence: 99%

“…(2). Let us now consider an alternative possibility widely used in the literature when dealing with EoS, which is to take the relativistic polytropic EoS [23][24][25][26] in order to reproduce the profile of the density as a function of the radial pressure, where K r and Γ r are free parameters. The plot is shown in Fig.…”

Section: Equations Of Statementioning

confidence: 99%

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Relativistic polytropic equations of state in Hořava gravity and Einstein-æther theory

Vernieri

2018

Phys. Rev. D

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The equations of state for a characteristic spacetime are studied in the context of the spherically symmetric interior exact and analytical solutions in Hořava gravity and Einstein-aether theory in which anisotropic fluids are considered. In particular, for a given anisotropic interior solution, the equations of state relating the density to the radial and tangential pressure are derived, by means of a polynomial best-fit. Moreover, the well-known relativistic polytropic equations of state are used in order to obtain the profile of the thermodynamical quantities inside the stellar object as provided by the specific exact solution considered. It is then shown that these equations of state need to be modified in order to account for the profiles of density and pressures.

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“…Such an approach was followed recently, e.g., in Refs. [3,4]. Yet another strategy was suggested in Ref.…”

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Comment on “Covariant Tolman-Oppenheimer-Volkoff equations. II. The anisotropic case”

Isayev

2018

Phys. Rev. D

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Recently, the covariant formulation of the Tolman-Oppenheimer-Volkoff (TOV) equations for studying the equilibrium structure of a spherically symmetric compact star in the presence of the pressure anisotropy in the interior of a star was presented in Ref.[1] [Phys. Rev. D 97 (2018) 124057]. It was suggested there that the anisotropic solution of these equations can be obtained by finding, first, the solution of the common TOV equations for the isotropic pressure, and then by solving the differential equation for the anisotropic pressure whose particular form was established on the basis of the covariant TOV equations. It turns out that the anisotropic pressure determined according to this scheme has a nonremovable singularity Π ∼ 1 r 2 in the center of a star, and, hence, the corresponding anisotropic solution cannot represent a physically relevant model of an anisotropic compact star. A new scheme for constructing the anisotropic solution, based on the covariant TOV equations, is suggested, which leads to the regularly behaved physical quantities in the interior of a star. A new algorithm is applied to build model anisotropic strange quark stars with the MIT bag model equation of state. * isayev@kipt.kharkov.ua

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General relativistic polytropes in anisotropic stars

Cited by 38 publications

References 53 publications

On the effect of anisotropy on stellar models

On the effect of anisotropy on stellar models

Relativistic polytropic equations of state in Hořava gravity and Einstein-æther theory

Comment on “Covariant Tolman-Oppenheimer-Volkoff equations. II. The anisotropic case”

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