scholarly journals Approximate Solutions of the Relativistic Gravitational Field Equations to Describe Clusters of Galaxies

1972 ◽  
Vol 25 (3) ◽  
pp. 299 ◽  
Author(s):  
MW Cook
Keyword(s):  
Gravitational Field ◽  
Approximate Solutions ◽  
Spherically Symmetric ◽  
Clusters Of Galaxies ◽  
Einstein Field Equations ◽  
Field Equations ◽  
Stellar Objects ◽  
Gravitational Field Equations ◽  
Local Fluctuations ◽  
Region 10

Approximate solutions to the Einstein field equations are found which describe a spherically symmetric inhomogeneity in a general Robertson?Walker model, i.e. one with an arbitrary equation of state. The approximation hypothesis is that the pressure deviates only slightly from uniformity, and it is found that the density may have quite large local fluctuations, e.g. by a factor of 106 over a region 10-2 Mpc in diameter. Reference is made to observed data to determine which categories of stellar objects may be described by the results.

Spherically symmetric static matter configurations with vanishing radial pressure

2014 ◽  
Vol 24 (01) ◽  
pp. 1550002 ◽  
Author(s):  
S. Thirukkanesh ◽  
M. Govender ◽  
D. B. Lortan
Keyword(s):  
Gravitational Field ◽  
Radial Pressure ◽  
Constant Density ◽  
Spherically Symmetric ◽  
Einstein Field Equations ◽  
Field Equations ◽  
New Family ◽  
Generating Method ◽  
Static Solutions ◽  
Special Case

We present a new family of spherically symmetric, static solutions of the Einstein field equations in isotropic, comoving coordinates. The radial pressure at each interior point of these models vanishes yet equilibrium is still possible. The constant density Florides solution which describes the gravitational field inside an Einstein cluster is obtained as a special case of our solution-generating method. We show that our solutions can be utilized to model strange star candidates such as Her. X-1, SAX J1808.4-3658(SS2), SAX J1808.4-3658(SS1) and PSR J1614-2230.

Thermodynamics of traversable wormholes in f(R,T) gravity

2021 ◽  
pp. 2150175
Author(s):  
Mudassar Rehman ◽  
Khalid Saifullah
Keyword(s):  
Gravitational Field ◽  
Spherically Symmetric ◽  
Field Equations ◽  
Matter Coupling ◽  
Gravitational Field Equations ◽  
Traversable Wormholes ◽  
Local Coordinates ◽  
Stress Energy ◽  
Minimal Curvature ◽  
Trapping Horizons

In this paper, we discuss thermodynamics for spherically symmetric and static traversable wormholes which include Morris–Thorne wormholes and charged wormholes in the background of [Formula: see text] gravity. The local coordinates have been used to find trapping horizons of these objects and generalized surface gravity has been worked out on the trapping horizons. The expression for the unified first law has also been derived from the gradient of Misner–Sharp energy with the help of gravitational field equations and from this law the first law of wormhole dynamics has been obtained. We have done this analysis for the simplest case of [Formula: see text] gravity where [Formula: see text], [Formula: see text] and [Formula: see text] being the traces of the Ricci and stress–energy tensors. Also, we have extended these thermodynamic results to non-minimal curvature-matter coupling.

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