A regular perfect fluid model for dense stars

2019 ◽  
Vol 34 (15) ◽  
pp. 1950115 ◽  
Author(s):  
Gabino Estevez-Delgado ◽  
Joaquin Estevez-Delgado ◽  
Jorge Mauricio Paulin-Fuentes ◽  
Nadiezhda Montelongo Garcia ◽  
Modesto Pineda Duran
Keyword(s):  
Perfect Fluid ◽  
Fluid Model ◽  
Einstein Equations ◽  
Compact Stars ◽  
Variable Pressure ◽  
Spherically Symmetric ◽  
Matter Distribution ◽  
Stellar Objects ◽  
Dense Stars ◽  
Decreasing Functions

We present an exact regular solution of Einstein equations for a static and spherically symmetric spacetime with a matter distribution of isotropic perfect fluid. The construction of the solution is realized assigning a regular potential [Formula: see text] and integrating the isotropic perfect fluid condition for the pressure. The resulting solution is physically acceptable, i.e. the geometry is regular and the hydrostatic variable pressure and density are positive regular monotonic decreasing functions, the speed of the sound is positive and smaller than the speed of the light. An important element of this solution is that its compactness value [Formula: see text] is in the characteristic range of compact stars, which makes a remarkable difference with other models with isotropic perfect fluid, this is [Formula: see text] so that we could represent compact stellar objects as neutron stars. In particular, for the maximum compactness of a star with a mass of [Formula: see text] the radius is [Formula: see text] and their central density [Formula: see text] is characteristic of compact stars.

A perfect fluid model for neutron stars

2018 ◽  
Vol 33 (40) ◽  
pp. 1850237 ◽  
Author(s):  
Gabino Estevez-Delgado ◽  
Joaquin Estevez-Delgado ◽  
Nadiezhda Montelongo Garcia ◽  
Modesto Pineda Duran
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Perfect Fluid ◽  
Fluid Model ◽  
Compact Stars ◽  
The Sun ◽  
Speed Of Light ◽  
Internal Solution ◽  
Maximum Value ◽  
Decreasing Functions

In this paper, we present a physically acceptable internal solution with a perfect fluid, which needs the pressure and density as regular, positive and monotonic decreasing functions and with a speed of sound positive and lower than the speed of light. This solution depends on a parameter [Formula: see text], and it is physically acceptable if [Formula: see text], the compactness has a maximum value for the maximum value of [Formula: see text] and it corresponds to [Formula: see text], thus the model can be applicable to the description of compact stars. In a complementary way, we present the description of a star with mass equal to the sun mass and radius of [Formula: see text] Km associated to the neutron star Her X-1, obtaining a central density [Formula: see text] which is characteristic of the neutron stars.

A generalized anisotropic model for super dense stars

2021 ◽  
pp. 2150070
Author(s):  
Joaquin Estevez-Delgado ◽  
Gabino Estevez-Delgado ◽  
Noel Enrique Rodríguez Maya ◽  
José Martínez Peña ◽  
Aurelio Tamez Murguía
Keyword(s):  
Radial Pressure ◽  
Compact Stars ◽  
Anisotropic Model ◽  
Speed Of Light ◽  
Matter Distribution ◽  
Sphere Model ◽  
Tangential Pressure ◽  
Relativistic Fluid ◽  
Causal Condition ◽  
Dense Stars

A static anisotropic relativistic fluid sphere model with regular geometry and finite hydrostatic functions is presented. In the interior of the sphere, the density, radial pressure and tangential pressure are positives, monotonically decreasing with increasing radius and the radial pressure vanishes at the surface of the matter distribution and is joined continuously to the exterior Schwarzschild’s solution at this surface. The speeds of the radial and tangential sound are positive and lower than the speed of light, that is, the causal condition is not violated, and also the behavior of these guarantees that the model is potentially stable. Furthermore, the range of the compactness ratio is characteristic of compact stars and it is shown that the effect of the anisotropy generates that the speed of the radial sound can behave as a function monotonically increasing or monotonically decreasing.

scholarly journals A perfect fluid model for compact stars

2019 ◽  
Vol 97 (9) ◽  
pp. 988-993 ◽  
Author(s):  
Gabino Estevez-Delgado ◽  
Joaquin Estevez-Delgado ◽  
Nadiezhda Montelongo García ◽  
Modesto Pineda Duran
Keyword(s):  
Perfect Fluid ◽  
Fluid Model ◽  
Compact Stars

scholarly journals A charged perfect fluid model with high compactness

2019 ◽  
Vol 65 (4 Jul-Aug) ◽  
pp. 382 ◽  
Author(s):  
G. Estevez-Delgado ◽  
J. Estevez-Delgado ◽  
M. Pineda Duran ◽  
N. Montelongo García ◽  
J.M. Paulin-Fuentes
Keyword(s):  
Electric Field ◽  
Perfect Fluid ◽  
Maxwell Equations ◽  
Fluid Model ◽  
Stellar Model ◽  
Compact Stars ◽  
Charged Fluid ◽  
Charge Parameter ◽  
Positive Functions ◽  
Increasing Function

A relativistic, static and spherically symmetrical stellar model is presented, constituted by a perfect charged fluid. This represents a generalization to the case of a perfect neutral fluid, whose construction is made through the solution to the Einstein-Maxwell equations proposing a form of gravitational potential  $g_{tt}$ and the electric field. The choice of electric field implies that this model supports values of compactness$u=GM/c^2R\leq 0.5337972212$, values higher than the case without electric charge ($u\leq 0.3581350065$), being this feature of relevance to get to represent compact stars. In addition, density and pressure are positive functions, bounded and decreasing monotones, the electric field is a monotonously increasing function as well as satisfying the condition of causality so the model is physically acceptable. In a complementary way, the internal behavior of the hydrostatic functions and their values are obtained taking as a data the corresponding to a star of $1 M_\odot$,for different values of the charge parameter, obtaining an interval for the central density $\rho_c\approx (7.9545,2.7279) 10^{19}$ $ Kg/m^3$ characteristic of compact stars.

scholarly journals ON NEGATIVE MASS

2013 ◽  
Vol 22 (12) ◽  
pp. 1341017 ◽  
Author(s):  
JONATHAN BELLETÊTE ◽  
M. B. PARANJAPE
Keyword(s):  
Free Parameter ◽  
Energy Condition ◽  
Einstein Equations ◽  
Dominant Energy Condition ◽  
Spherically Symmetric ◽  
De Sitter ◽  
Matter Distribution ◽  
Negative Mass ◽  
Schwarzschild Solution ◽  
Tunneling Transition

The Schwarzschild solution to the matter free, spherically symmetric Einstein equations has one free parameter, the mass. But the mass can be of any sign. What is the meaning of the negative mass solutions? The answer to this question for the case of a pure Schwarzschild negative mass black solution is still elusive, however, in this essay, we will consider negative mass solutions within a Schwarzschild–de Sitter geometry. We show that there exist reasonable configurations of matter, bubbles of distributions of matter, that satisfy the dominant energy condition everywhere, that are nonsingular and well behaved everywhere, but correspond to the negative mass Schwarzschild–de Sitter geometry outside the matter distribution. These negative mass bubbles could occur as the end state of a quantum tunneling transition.

ON THE INTERACTION OF BUBBLES WITH GRAVITATIONAL AND MATTER FIELDS

1992 ◽  
Vol 07 (20) ◽  
pp. 1779-1789 ◽  
Author(s):  
ANZHONG WANG
Keyword(s):  
Electromagnetic Field ◽  
Scalar Field ◽  
Perfect Fluid ◽  
Space Time ◽  
Distribution Theory ◽  
Einstein Equations ◽  
Spherically Symmetric ◽  
Bubble Wall ◽  
Bianchi Identities ◽  
Matter Fields

The space-time containing a single spherically symmetric bubble is studied by using the distribution theory. The Einstein equations on the bubble wall are given explicitly in terms of the discontinuities of metric coefficients and their derivatives, The interaction of a bubble with surrounding gravitational and matter fields is also investigated by the “generalized” Bianchi identities. In particular, it is found that an electromagnetic field does not interact with any bubble, and is continuous across the bubble wall without reflecting or absorbing, while the interaction of a bubble produced with a scalar field or a perfect fluid is possible.

A study of anisotropic compact stars based on embedding class 1 condition

2019 ◽  
Vol 28 (09) ◽  
pp. 1950116 ◽  
Author(s):  
S. K. Maurya ◽  
Debabrata Deb ◽  
Saibal Ray ◽  
P. K. F. Kuhfittig
Keyword(s):  
Stellar Model ◽  
Einstein Equations ◽  
Compact Stars ◽  
Energy Conditions ◽  
Physical Parameters ◽  
Matter Distribution ◽  
Generalized Model ◽  
Anisotropic Factor ◽  
Class 1 ◽  
Metric Functions

This paper discusses a generalized model for compact stars, assumed to be anisotropic in nature due to the presence of highly dense and ultra-relativistic matter distribution. After embedding the 4D Riemannian space locally and isometrically into a 5D pseudo-Euclidean space, we solve the Einstein equations by employing a class of physically acceptable metric functions. The physical properties determined include the anisotropic factor showing that the anisotropy is zero at the center and maximum at the surface. Other boundary conditions yield the values of various parameters needed for rendering the numerous plots and also led to the EOS parameters. It is further determined that the usual energy conditions are satisfied and that the compact structures are stable, based on several criteria, viz., the equilibrium of forces, Herrera cracking concept, adiabatic index, etc. We note that the proposed stellar model satisfies the Buchdahl condition. Finally, the values of the numerous constants and physical parameters are determined, specifically for the compact stellar object [Formula: see text], which we choose as a representative of the compact stars to present the analysis of the obtained results. Finally, we show that the present generalized model can justify most of the compact stars including white dwarfs and ultra-dense compact stars for a suitable tuning of the parametric values of [Formula: see text].

Sign in / Sign up

Export Citation Format

Share Document