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.

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 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.

INFLATIONARY SCENARIO IN BRANS–DICKE THEORY FOR BIANCHI VI0 SPACE–TIME MODEL

2003 ◽  
Vol 12 (01) ◽  
pp. 129-143 ◽  
Author(s):  
SUBENOY CHAKRABORTY ◽  
ARABINDA GHOSH
Keyword(s):  
Equation Of State ◽  
Perfect Fluid ◽  
Analytical Solutions ◽  
Fluid Model ◽  
Space Time ◽  
Time Model ◽  
Exact Analytical Solutions ◽  
Exponential Expansion ◽  
Barotropic Equation ◽  
Space Time Model

We have investigated perfect fluid model in Brans–Dicke theory for Bianchi VI 0 space–time and have obtained exact analytical solutions considering barotropic equation of state. These solutions have been analyzed for different values of the parameters involved and some of them have shown a period of exponential expansion.

BRANS–DICKE THEORY IN BIANCHI III MODEL AND INFLATIONARY SCENARIO

2002 ◽  
Vol 11 (03) ◽  
pp. 391-404 ◽  
Author(s):  
NARAYAN CHANDRA CHAKRABORTY ◽  
SUBENOY CHAKRABORTY
Keyword(s):  
Equation Of State ◽  
Perfect Fluid ◽  
Analytical Solutions ◽  
Fluid Model ◽  
Space Time ◽  
Exact Analytical Solutions ◽  
Inflationary Scenario ◽  
Bianchi Iii ◽  
Barotropic Equation

Brans–Dicke theory with perfect fluid model has been considered in Bianchi III space–time and exact analytical solutions are presented with barotropic equation of state. These solutions have been analyzed and some of them have shown the properties of inflationary scenario.

QUANTUM PERFECT FLUID COSMOLOGICAL MODEL AND ITS CLASSICAL ANALOGUE

2002 ◽  
Vol 17 (20) ◽  
pp. 2749-2749
Author(s):  
A. B. BATISTA ◽  
J. C. FABRIS ◽  
S. V. B. GONCALVES ◽  
J. TOSSA
Keyword(s):  
Perfect Fluid ◽  
Fluid Model ◽  
Classical Model ◽  
Free Particle ◽  
Stiff Matter ◽  
Bouncing Universe ◽  
Quantization Of Gravity ◽  
Barotropic Equation ◽  
Classical Analogue ◽  
Perfect Fluid Models

The quantization of gravity coupled to a perfect fluid model leads to a Schrödinger-like equation, where the matter variable plays the role of time. The wave function can be determined, in the flat case, for an arbitrary barotropic equation of state p = α ρ; solutions can also be found for the radiative non-flat case. The wave packets are constructed, from which the expectation value for the scale factor is determined. The quantum scenarios reveal a bouncing Universe, free from singularity. Such quantum cosmological perfect fluid models admit a universal classical analogue, represented by the addition, to the ordinary classical model, of a repulsive stiff matter fluid1,2. The existence of this universal classical analogue may imply that this perfect fluid coupled to gravity model is not a real quantum system. The quantum cosmological perfect fluid model is, for a flat spatial section, formally equivalent to a free particle in ordinary quantum mechanics, for any value of α, while the radiative non-flat case is equivalent to the harmonic oscillator. The repulsive fluid needed to reproduce the quantum results is the same in both cases.

scholarly journals QUANTUM RAINBOW COSMOLOGICAL MODEL WITH PERFECT FLUID

2013 ◽  
Vol 22 (13) ◽  
pp. 1350079 ◽  
Author(s):  
BARUN MAJUMDER
Keyword(s):  
Quantum Mechanics ◽  
Cosmological Model ◽  
Perfect Fluid ◽  
Fluid Model ◽  
Cosmic Time ◽  
Wave Functions ◽  
Interpretation Of Quantum Mechanics ◽  
Many Worlds ◽  
The Many

Isotropic quantum cosmological perfect fluid model is studied in the formalism of Rainbow gravity. It is found that the only surviving matter degree of freedom played the role of cosmic time. With the suitable choice of the Rainbow functions it is possible to find the wave packet naturally from the superposition of the wave functions of the Schrödinger–Wheeler–deWitt equation. The many-worlds interpretation of quantum mechanics is applied to investigate the behavior of the scale factor and the behavior is found to depend on the operator ordering. It is shown that the model in the Rainbow framework may avoid singularity yielding a bouncing nonsingular universe.

A relativistic two-fluid model of compact stars

2017 ◽  
Vol 32 (10) ◽  
pp. 1750055 ◽  
Author(s):  
Koushik Chakraborty ◽  
Farook Rahaman ◽  
Arkopriya Mallick
Keyword(s):  
Quark Matter ◽  
Fluid Model ◽  
Compact Star ◽  
Conformal Symmetry ◽  
Compact Objects ◽  
Compact Stars ◽  
Baryonic Matter ◽  
Spacetime Geometry ◽  
Two Fluid Model ◽  
The Masses

We propose a relativistic model of compact star admitting conformal symmetry. Quark matter and baryonic matter which are considered as two different fluids, constitute the star. We define interaction equations between the normal baryonic matter and the quark matter and study the physical situations for repulsive, attractive and zero interaction between the constituent matters. The measured value of the Bag constant is used to explore the spacetime geometry inside the star. From the observed values of the masses of some compact objects, we have obtained theoretical values of the radii. Theoretical values of the radii match well with the previous predictions for such compact objects.

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