scholarly journals Spherically symmetric models: Separating expansion from contraction in models with anisotropic pressures

2012 ◽  
Author(s):  
José P. Mimoso ◽  
Morgan Le Delliou ◽  
Filipe C. Mena
Keyword(s):  
Spherically Symmetric ◽  
Anisotropic Pressures

scholarly journals Chaplygin strange stars in presence of quintessence

2021 ◽  
Vol 36 (29) ◽  
Author(s):  
Joaquin Estevez-Delgado ◽  
Modesto Pineda Duran ◽  
Arthur Cleary-Balderas ◽  
Noel Enrique Rodríguez Maya ◽  
José Martínez Peña
Keyword(s):  
Radial Pressure ◽  
State Equation ◽  
Stellar Model ◽  
Maximum Density ◽  
Spherically Symmetric ◽  
Tangential Pressure ◽  
Strange Stars ◽  
Ordinary Matter ◽  
Anisotropic Pressures ◽  
Symmetric Spacetime

Starting from a regular, static and spherically symmetric spacetime, we present a stellar model formed by two sources of ordinary and quintessence matter both with anisotropic pressures. The ordinary matter, with density [Formula: see text], is formed by a fluid with a state equation type Chaplygin [Formula: see text] for the radial pressure. And the quintessence matter, with density [Formula: see text], has a state equation [Formula: see text] for the radial pressure and [Formula: see text] for the tangential pressure with [Formula: see text]. The model satisfies the required conditions to be physically acceptable and additionally the solution is potentially stable, i.e. [Formula: see text] according to the cracking concept, and it also satisfies the Harrison–Zeldovich–Novikov criteria. We describe in a graphic manner the behavior of the solution for the case in which the mass is [Formula: see text] and radius [Formula: see text][Formula: see text]km which matches the star EXO 1785-248, from where we obtain the maximum density [Formula: see text] for the values of the parameters [Formula: see text], [Formula: see text].

scholarly journals On the stability of (M theory) stars against collapse: Role of anisotropic pressures

2015 ◽  
Vol 30 (27) ◽  
pp. 1550165
Author(s):  
S. Kalyana Rama
Keyword(s):  
Crucial Role ◽  
Equations Of State ◽  
Higher Dimensions ◽  
Singular Solutions ◽  
Spherically Symmetric ◽  
Stability Of Stars ◽  
The Stability ◽  
M Theory ◽  
Anisotropic Pressures

Unitarity of evolution in gravitational collapses implies existence of macroscopic stable horizonless objects. With such objects in mind, we study the effects of anisotropy of pressures on the stability of stars. We consider stars in four or higher dimensions and also stars in M theory made up of (intersecting) branes. Taking the stars to be static, spherically symmetric and the equations of state to be linear, we study “singular solutions” and the asymptotic perturbations around them. Oscillatory perturbations are likely to imply instability. We find that nonoscillatory perturbations, which may imply stability, are possible if an appropriate amount of anisotropy is present. This result suggests that it may be possible to have stable horizonless objects in four or any higher dimensions, and that anisotropic pressures may play a crucial role in ensuring their stability.

The two-body problem: an effective-one-body approach

2018 ◽  
Author(s):  
Nathalie Deruelle ◽  
Jean-Philippe Uzan
Keyword(s):  
Body Problem ◽  
Equations Of Motion ◽  
Reaction Force ◽  
Kerr Black Hole ◽  
Radiation Reaction ◽  
Spherically Symmetric ◽  
Geodesic Motion ◽  
Two Body Problem ◽  
Symmetric Spacetime ◽  
Radiation Reaction Force

This chapter presents the basics of the ‘effective-one-body’ approach to the two-body problem in general relativity. It also shows that the 2PN equations of motion can be mapped. This can be done by means of an appropriate canonical transformation, to a geodesic motion in a static, spherically symmetric spacetime, thus considerably simplifying the dynamics. Then, including the 2.5PN radiation reaction force in the (resummed) equations of motion, this chapter provides the waveform during the inspiral, merger, and ringdown phases of the coalescence of two non-spinning black holes into a final Kerr black hole. The chapter also comments on the current developments of this approach, which is instrumental in building the libraries of waveform templates that are needed to analyze the data collected by the current gravitational wave detectors.

Spherically Symmetric Gravitational Fields

1965 ◽  
Vol 6 (1) ◽  
pp. 1-5 ◽  
Author(s):  
P. G. Bergmann ◽  
M. Cahen ◽  
A. B. Komar
Keyword(s):  
Spherically Symmetric ◽  
Gravitational Fields
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