scholarly journals Gravitational collapse of an isentropic perfect fluid with a linear equation of state

2004 ◽  
Vol 21 (15) ◽  
pp. 3645-3653 ◽  
Author(s):  
Rituparno Goswami ◽  
Pankaj S Joshi
Keyword(s):  
Equation Of State ◽  
Linear Equation ◽  
Perfect Fluid ◽  
Gravitational Collapse

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 Vorticity of a Perfect Fluid Undergoing a Gravitational Collapse

1976 ◽  
Vol 29 (5) ◽  
pp. 413 ◽  
Author(s):  
DP Mason
Keyword(s):  
Magnetic Field ◽  
General Relativity ◽  
Equation Of State ◽  
Energy Density ◽  
Perfect Fluid ◽  
Gravitational Collapse ◽  
Propagation Equation ◽  
Spatial Geometry ◽  
Relativistic Magnetohydrodynamics ◽  
The Magnetic Field

The vorticity propagation equation for a perfect fluid in general relativity is derived in a form which is the same as that of Maxwell's equation for the magnetic field four-vector in relativistic magnetohydrodynamics. Starting from this result, an expression for the change of vorticity during a gravitational collapse is obtained in terms of the spatial geometry, using a procedure similar to that introduced by Cocke (1966) in relativistic magnetohydrodynamics. It is assumed that the equation of state of the fluid is p = 1Xp" where IX is a constant and p, is the total proper energy density. If t < IX :s;; 1, it is found that the vorticity tends to zero during an isotropic collapse, in agreement with a result obtained previously by Ellis (1973) using a different procedure. Nonisotropic collapses are also considered. The dynamical importance of vorticity in a gravitational collapse is examined by considering the behaviour of w2 /p,.

scholarly journals Emergent Universe as an interaction in the dark sector

2017 ◽  
Vol 32 (28) ◽  
pp. 1750152
Author(s):  
Emiliano Marachlian ◽  
I. E. Sánchez G. ◽  
Osvaldo P. Santillán
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Equation Of State ◽  
Linear Equation ◽  
Vacuum Energy ◽  
Cosmological Parameters ◽  
Emergent Universe ◽  
Dark Sector ◽  
Cosmological Scenario ◽  
Friedmann Robertson Walker

A cosmological scenario where dark matter interacts with a variable vacuum energy for a spatially flat Friedmann–Robertson–Walker (FRW) spacetime is proposed and analyzed to show that with a linear equation of state and a particular interaction in the dark sector it is possible to get a model of an Emergent Universe. In addition, the viability of two particular models is studied by taking into account the recent observations. The updated observational Hubble data and the JLA supernovae data are used in order to constraint the cosmological parameters of the models and estimate the amount of dark energy in the radiation era. It is shown that the two models fulfil the severe bounds of [Formula: see text] at the 2[Formula: see text] level of Planck.

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