An anisotropic model for represent compact stars

Estevez-Delgado, Joaquin; Cabrera, Jose Vega; Ceballos, Joel Arturo Rodriguez; Paulin-Fuentes, Jorge Mauricio

doi:10.1142/s0217732320501321

“…Then the anisotropic tensor may be expressed through three scalar functions defined as (see [46] for details): The heat flux vector may be defined in terms of the two tetrad components q (1) and q (2) , as: q µ = q (1) e (1) µ + q (2) e (2) µ (37) or, in coordinate components (see [45])…”

Section: The Axially Symmetric Casementioning

confidence: 99%

Stability of the isotropic pressure condition

Herrera

2020

Preprint

0

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We investigate the conditions for the (in)stability of the isotropic pressure condition in collapsing spherically symmetric, dissipative fluid distributions. It is found that dissipative fluxes, and/or energy density inhomogeneities and/or the appearance of shear in the fluid flow, force any initially isotropic configuration to abandon such a condition, generating anisotropy in the pressure. To reinforce this conclusion we also present some arguments concerning the axially symmetric case. The consequences ensuing our results are analyzed.

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“…Solutions with perfect fluid tend to be more complicated to obtain than charged solutions or anisotropic solutions, i.e., fluids that present differences between the radial and tangential pressures, since the number of restrictions that can be imposed is lower for the case of a perfect fluid. Even the solutions with perfect fluid [1][2][3][4][5][6][7][8][9][10] can be used as seed solutions to obtain generalizations to the charged [11][12][13][14][15][16][17] or anisotropic [18][19][20][21][22][23][24] cases. There is also a method to obtain the solution of a perfect fluid from a seed solution of perfect fluid, this mechanism utilizes the existence of a second order differential equation that relates the metric coefficients g tt and g rr , although this one can only generate an exact new solution, return to an exact solution that was already known or it can even be that the resulting integral equation does not admit a primitive function [25,26].…”

Section: Introductionmentioning

confidence: 99%

An Einstein-Maxwell interior solution obeying Karmarkar condition

Estevez-Delgado,

Estevez Delgado,

Cleary-Balderas

et al. 2024

Rev. Mex. Fís.

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For the Einstein-Maxwell equation system, with perfect fluid in a static and spherically symmetrical spacetime, we report an analytical internal solution which is obtained by imposing the Karmarkar condition, the behaviour of the solution is such that the density and pressures are monotonically decreasing functions while the electric field function is a monotonically increasing function that is adequate to represent compact objects. In particular we have these characteristics for the observational values of mass (1.29 ± 0.05) M⊙ and radius (8.831 ± 0.09) km of the star SMC X-4. We will analyze the two extremes the one of minimum compactness umin = 0.20523 (M = 1.24 M⊙, R = 8.921 km) and the one of maximum compactness umax = 0.22635 (M = 1.34 M⊙, R = 8.741 km), resulting that the electric charge Qumin ∈ [1.5279, 1.8498]1020C and Qumax ∈ [1.6899, 1.9986]1020C respectively, implying that the case with higher compactness has a higher electric charge. Also in a graphic manner, it is shown that the causality condition is satisfied and that the solution is stable against infinitesimal radial adiabatic perturbation and also in regards to the Harrison-Novikov-Zeldovich criteria

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“…On the other hand there have been some approaches at a stellar level to describe compact objects [20][21][22][23], considering that the interior of the stars is formed by ordinary neutral matter [24][25][26][27][28][29][30], ordinary charged matter [31][32][33][34][35][36][37], and also by sources which are a combination of ordinary matter and quintessence dark energy, consistent with neutron stars [38]. Neutron or quark stars are not exclusively composed of neutrons or quarks, respectively, but rather these stars are formed predominantly by one of those particles.…”

Section: Introductionmentioning

confidence: 99%

On quintessence star model and strange star

Estevez-Delgado

¹

,

Estevez-Delgado

²

2020

Self Cite

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The astronomical observations on the accelerated expansion of the universe generate the possibility that the internal matter of the stars is not only formed by ordinary matter but also by matter with negative pressure. We discuss the existence of stars formed by the coexistence of two types of fluids, one associated to quintessence dark matter described by the radial and tangential pressures $$(P_{rq},P_{tq})$$ ( P rq , P tq ) and the density $$\rho _{q}$$ ρ q characterized by a parameter $$-1<w<-\frac{1}{3}$$ - 1 < w < - 1 3 and ordinary matter described by an anisotropic fluid with radial pressure of a strange star given by the MIT Bag model $$P_r=\frac{1}{3}(c^2\rho -4B_g)$$ P r = 1 3 ( c 2 ρ - 4 B g ) and tangential pressure $$P_t=\frac{1}{3}(c^2\rho -4B_g)-\frac{3}{2}(1+w)c^2\rho _q$$ P t = 1 3 ( c 2 ρ - 4 B g ) - 3 2 ( 1 + w ) c 2 ρ q , in which the effect is reflected of the quintessence dark matter over the ordinary matter. Via a theorem we show that the geometry that describes this interaction is equivalent to that of a perfect fluid with ordinary matter. Taking as geometry the one associated with a model for neutron stars, a physically acceptable and stable model is obtained. The application to the star Her X-1, as a candidate to a strange quark star, generates for us a value of the MIT Bag constant $$B_g = 97.0048\,\mathrm{Mev}/\mathrm{fm}^3$$ B g = 97.0048 Mev / fm 3 , which is found to be inside the expected interval.

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An anisotropic model for represent compact stars

Cited by 14 publications

References 54 publications

Stability of the isotropic pressure condition

Stability of the isotropic pressure condition

An Einstein-Maxwell interior solution obeying Karmarkar condition

On quintessence star model and strange star

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