scholarly journals ELECTROMAGNETIC FIELD IN SOME ANISOTROPIC STIFF FLUID UNIVERSES

1995 ◽  
Vol 10 (28) ◽  
pp. 2095-2101 ◽  
Author(s):  
LUIS O. PIMENTEL
Keyword(s):  
Electromagnetic Field ◽  
Equation Of State ◽  
Exact Solutions ◽  
Perfect Fluid ◽  
Einstein Equations ◽  
Stiff Fluid ◽  
Field Equations ◽  
Material Content ◽  
Stiff Equation ◽  
The Family

The electromagnetic field is studied in a family of exact solutions of the Einstein equations whose material content is a perfect fluid with stiff equation of state (p=ε). The field equations are solved exactly for several members of the family.

Investigating cosmology with equation of state

2019 ◽  
Vol 97 (7) ◽  
pp. 752-760 ◽  
Author(s):  
M. Farasat Shamir ◽  
Adnan Malik
Keyword(s):  
Equation Of State ◽  
Exact Solutions ◽  
Scalar Potential ◽  
State Parameter ◽  
Field Equations ◽  
Equation Of State Parameter ◽  
Radiation Universe ◽  
Modified Formula ◽  
Friedmann Robertson Walker ◽  
Dust Universe

The aim of this paper is to investigate the field equations of modified [Formula: see text] theory of gravity, where R and [Formula: see text] represent the Ricci scalar and scalar potential, respectively. We consider the Friedmann–Robertson–Walker space–time for finding some exact solutions by using different values of equation of state parameter. In this regard, different possibilities of the exact solutions have been discussed for dust universe, radiation universe, ultra-relativistic universe, sub-relativistic universe, stiff universe, and dark energy universe. Mainly power law and exponential forms of the scale factor are chosen for the analysis.

Charged anisotropic static cylindrically symmetric models

2013 ◽  
Vol 91 (2) ◽  
pp. 113-119 ◽  
Author(s):  
M. Sharif ◽  
H. Ismat Fatima
Keyword(s):  
Electromagnetic Field ◽  
Equation Of State ◽  
Energy Density ◽  
Symmetric Space ◽  
Radial Pressure ◽  
Matter Distribution ◽  
Field Equations ◽  
Stellar Objects ◽  
Cylindrically Symmetric ◽  
Barotropic Equation

In this paper, we investigate exact solutions of the field equations for charged, anisotropic, static, cylindrically symmetric space–time. We use a barotropic equation of state linearly relating the radial pressure and energy density. The analysis of the matter variables indicates a physically reasonable matter distribution. In the most general case, the central densities correspond to realistic stellar objects in the presence of anisotropy and charge. Finally, we conclude that matter sources are less affected by the electromagnetic field.

scholarly journals Plausible families of compact objects with a nonlocal equation of state

2013 ◽  
Vol 91 (4) ◽  
pp. 328-336 ◽  
Author(s):  
H. Hernández ◽  
L.A. Núñez
Keyword(s):  
Equation Of State ◽  
Total Mass ◽  
Radial Pressure ◽  
Compact Objects ◽  
Einstein Equations ◽  
Matter Distribution ◽  
Nonlocal Equation ◽  
The Family ◽  
Model Independent ◽  
Physical Variables

We present the plausibility of some models emerging from an algorithm devised to generate a one-parameter family of interior solutions for the Einstein equations. We explore how their physical variables change as the family parameter varies. The models studied correspond to anisotropic spherical matter configurations having a nonlocal equation of state. This particular type of equation of state, with no causality problems, provides at a given point the radial pressure not only as a function of the density but as a functional of the enclosed matter distribution. We have found that there are several model-independent tendencies as the parameter increases: the equation of state tends to be stiffer and the total mass becomes half of its external radius. Profiting from the concept of cracking of materials in general relativity, we obtain that these models become more potentially stable as the family parameter increases.

ALGORITHMIC CONSTRUCTION OF EXACT SOLUTIONS FOR NEUTRAL STATIC PERFECT FLUID SPHERES

2013 ◽  
Vol 22 (09) ◽  
pp. 1350052 ◽  
Author(s):  
SUDAN HANSRAJ ◽  
DANIEL KRUPANANDAN
Keyword(s):  
Exact Solutions ◽  
Perfect Fluid ◽  
Complete Solution ◽  
Positive Definiteness ◽  
Energy Conditions ◽  
Einstein Field Equations ◽  
Field Equations ◽  
New Exact Solutions ◽  
Algorithmic Construction ◽  
Fluid Spacetimes

Although it ranks amongst the oldest of problems in classical general relativity, the challenge of finding new exact solutions for spherically symmetric perfect fluid spacetimes is still ongoing because of a paucity of solutions which exhibit the necessary qualitative features compatible with observational evidence. The problem amounts to solving a system of three partial differential equations in four variables, which means that any one of four geometric or dynamical quantities must be specified at the outset and the others should follow by integration. The condition of pressure isotropy yields a differential equation that may be interpreted as second-order in one of the space variables or also as first-order Ricatti type in the other space variable. This second option has been fruitful in allowing us to construct an algorithm to generate a complete solution to the Einstein field equations once a geometric variable is specified ab initio. We then demonstrate the construction of previously unreported solutions and examine these for physical plausibility as candidates to represent real matter. In particular we demand positive definiteness of pressure, density as well as a subluminal sound speed. Additionally, we require the existence of a hypersurface of vanishing pressure to identify a radius for the closed distribution of fluid. Finally, we examine the energy conditions. We exhibit models which display all of these elementary physical requirements.

NONMINIMAL COUPLING, QUARTIC POTENTIAL AND PERFECT FLUID COSMOLOGIES

1995 ◽  
Vol 04 (06) ◽  
pp. 767-779 ◽  
Author(s):  
S. CAPOZZIELLO ◽  
R. DE RITIS ◽  
C. RUBANO ◽  
P. SCUDELLARO
Keyword(s):  
Scalar Field ◽  
Equation Of State ◽  
Exact Solutions ◽  
Perfect Fluid ◽  
Einstein Gravity ◽  
Nonminimal Coupling ◽  
Stiff Matter ◽  
Quartic Potential ◽  
Fluid Matter

Perfect-fluid matter, satisfying the equation of state p=(γ−1)ρ, is considered in cosmologies where the geometry is nonminimally coupled with a scalar field ɸ and the potential of ɸ is λɸ4+Λ. Exact solutions are found when γ is a constant describing the ordinary forms of matter (γ=1, dust, γ=4/3, radiation, γ=2, stiff matter and γ=0, scalar field matter) and a discussion is done in order to recover Einstein gravity and the Newton constant observed today. The various solutions can be classified according to the different values of γ, λ and Λ.

scholarly journals Nonstatic Spherically Symmetric Solutions for a Perfect Fluid in General Relativity

1976 ◽  
Vol 29 (2) ◽  
pp. 113 ◽  
Author(s):  
N Chakravarty ◽  
SB Dutta Choudhury ◽  
A Banerjee
Keyword(s):  
General Relativity ◽  
Exact Solutions ◽  
Perfect Fluid ◽  
Dynamical Behaviour ◽  
Symmetric Distribution ◽  
Spherically Symmetric ◽  
Field Equations ◽  
Spherically Symmetric Solutions ◽  
Spherically Symmetric Distribution ◽  
General Method

A general method is described by which exact solutions of Einstein's field equations are obtained for a nonstatic spherically symmetric distribution of a perfect fluid. In addition to the previously known solutions which are systematically derived, a new set of exact solutions is found, and the dynamical behaviour of the corresponding models is briefly discussed.

scholarly journals CHARGED PERFECT FLUID CONFIGURATIONS WITH A DILATON FIELD

2005 ◽  
Vol 20 (11) ◽  
pp. 821-831 ◽  
Author(s):  
STOYTCHO S. YAZADJIEV
Keyword(s):  
Equation Of State ◽  
Nonlinear Equation ◽  
Helmholtz Equation ◽  
Linear Equation ◽  
Perfect Fluid ◽  
Constant Curvature ◽  
Interior Solution ◽  
Dilaton Field ◽  
Field Equations ◽  
Interior Solutions

We examine static charged perfect fluid configurations in the presence of a dilaton field. A method for construction of interior solutions is given. An explicit example of an interior solution which matches continuously the external Gibbons–Maeda–Garfinkle–Horowitz–Strominger solution is presented. Extremely charged perfect fluid configurations with a dilaton are also examined. We show that there are two types of extreme configurations. For each type the field equations are reduced to a single nonlinear equation on a space of a constant curvature. In the particular case of a perfect fluid with a linear equation of state, the field equations of the first type configurations are reduced to a Helmholtz equation on a space with a constant curvature. An explicit example of an extreme configuration is given and discussed.

scholarly journals LRS Bianchi I model with perfect fluid equation-of-state

2019 ◽  
Vol 28 (03) ◽  
pp. 1950056 ◽  
Author(s):  
Vijay Singh ◽  
Aroonkumar Beesham
Keyword(s):  
Equation Of State ◽  
General Solution ◽  
Perfect Fluid ◽  
Vacuum Energy ◽  
Energy Model ◽  
Field Equations ◽  
Systematic Treatment ◽  
Fluid Equation ◽  
Stiff Matter ◽  
Bianchi I

The general solution of the field equations in LRS Bianchi-I spacetime with perfect fluid equation-of-state (EoS) is presented. The models filled with dust, vacuum energy, Zel’dovich matter and disordered radiation are studied in detail. A unified and systematic treatment of the solutions is presented, and some new solutions are found. The dust, stiff matter and disordered radiation models describe only a decelerated universe, whereas the vacuum energy model exhibits a transition from a decelerated to an accelerated phase.

A class of exact solutions of certain classical field equations in general relativity

1962 ◽  
Vol 267 (1328) ◽  
pp. 1-10 ◽  
Keyword(s):  
General Relativity ◽  
Electromagnetic Field ◽  
Exact Solutions ◽  
Mass Density ◽  
Classical Field ◽  
Dirac Field ◽  
Field Equations ◽  
Second Quantization ◽  
The Third ◽  
Pseudo Scalar

This paper deals with certain model statical universes representing exact solutions of some field equations in general relativity. Three universes of this type are discussed. They correspond to combinations of gravitation respectively with (i) electromagnetic field, (ii) scalar or pseudo-scalar field, (iii) Maxwell-Dirac field. Such statical solutions are possible in the first two cases only if mass density and charge density are equal in magnitude, and in the third case only if mass and charge are equal in magnitude, so that matter is in equilibrium under the action of gravitation and other forces. The field equations, in this work, are classical in the sense that no second quantization is involved.

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