scholarly journals STABLE INFLATIONARY DISSIPATIVE COSMOLOGIES

2000 ◽  
Vol 09 (01) ◽  
pp. 43-55 ◽  
Author(s):  
LUIS P. CHIMENTO ◽  
ALEJANDRO S. JAKUBI ◽  
DIEGO PAVON
Keyword(s):  
Gravitational Field ◽  
Previous Analysis ◽  
De Sitter ◽  
Cosmic Expansion ◽  
Imperfect Fluid ◽  
The Stability

The stability of the de Sitter era of cosmic expansion in spatially curved homogeneous isotropic universes is studied. The source of the gravitational field is an imperfect fluid such that the parameters that characterize it may change with time. In this way we extend our previous analysis for spatially-flat spaces as well as the work of Barrow.

On the stability of the Earth's gravitational field

1983 ◽  
Vol 26 (2) ◽  
pp. 187-188
Author(s):  
Yu D Bulanzhe ◽  
Yu E Nesterikhin ◽  
N P Pariĭskiĭ
Keyword(s):  
Gravitational Field ◽  
Earth’S Gravitational Field ◽  
The Stability

scholarly journals Stability of the Regular Hayward Thin-Shell Wormholes

2016 ◽  
Vol 2016 ◽  
pp. 1-13 ◽  
Author(s):  
M. Sharif ◽  
Saadia Mumtaz
Keyword(s):  
Black Hole ◽  
Thin Shell ◽  
Energy Conditions ◽  
Stability Conditions ◽  
Energy Tensor ◽  
Stress Energy Tensor ◽  
Cosmic Expansion ◽  
Stress Energy ◽  
Thin Shell Wormholes ◽  
The Stability

The aim of this paper is to construct regular Hayward thin-shell wormholes and analyze their stability. We adopt Israel formalism to calculate surface stresses of the shell and check the null and weak energy conditions for the constructed wormholes. It is found that the stress-energy tensor components violate the null and weak energy conditions leading to the presence of exotic matter at the throat. We analyze the attractive and repulsive characteristics of wormholes corresponding toar>0andar<0, respectively. We also explore stability conditions for the existence of traversable thin-shell wormholes with arbitrarily small amount of fluid describing cosmic expansion. We find that the space-time has nonphysical regions which give rise to event horizon for0<a0<2.8and the wormhole becomes nontraversable producing a black hole. The nonphysical region in the wormhole configuration decreases gradually and vanishes for the Hayward parameterl=0.9. It is concluded that the Hayward and Van der Waals quintessence parameters increase the stability of thin-shell wormholes.

Charged gravastars in f(R,T,RμνTμν) gravity

2021 ◽  
pp. 2150084
Author(s):  
Z. Yousaf ◽  
M. Z. Bhatti
Keyword(s):  
Perfect Fluid ◽  
Energy Momentum Tensor ◽  
Equations Of State ◽  
Mathematical Formulation ◽  
Momentum Tensor ◽  
Spherically Symmetric ◽  
De Sitter ◽  
The Stability ◽  
Physical Features ◽  
Modified Theory

We explore the aspects of the electromagnetism on the stability of gravastar in a particular modified theory, i.e. [Formula: see text] where [Formula: see text], [Formula: see text] is the Ricci scalar and [Formula: see text] is the trace of energy–momentum tensor. We assume a spherically symmetric static metric coupled comprising of perfect fluid in the presence of electric charge. The purpose of this paper is to extend the results of [S. Ghosh, F. Rahaman, B. K. Guha and S. Ray, Phys. Lett. B 767 (2017) 380.] to highlight the effects of [Formula: see text] gravity in the formation of charged gravastars. We demonstrated the mathematical formulation, utilizing different equations of state, for the three respective regions (i.e. inner, shell, exterior) of the gravastar. We have matched smoothly the interior de Sitter and the exterior Reissner–Nordström metric at the hypersurface. At the end we extracted few conclusions by working on the physical features of the charged gravastar, mathematically and graphically.

scholarly journals CLASSICAL STABILITY OF BLACK HOLES UNDER MASSLESS DIRAC PERTURBATIONS

2012 ◽  
Vol 21 (13) ◽  
pp. 1250092 ◽  
Author(s):  
A. LÓPEZ-ORTEGA
Keyword(s):  
Black Holes ◽  
Positive Definite ◽  
Dirac Field ◽  
De Sitter ◽  
Deformation Method ◽  
Effective Potentials ◽  
Classical Stability ◽  
Region Exterior ◽  
Classical Fields ◽  
The Stability

In a D-dimensional maximally symmetric spacetime we simplify the massless Dirac equation to two decoupled wavelike equations with effective potentials. Furthermore in D-dimensional Schwarzschild and Schwarzschild de Sitter (SdS) black holes we note that for the massless Dirac field moving in the region exterior to the event horizon at least one of the effective potentials is not positive definite. Therefore the classical stability of these black holes against this field is not guaranteed. Here with the help of the S-deformation method, we state their classical stability against the massless Dirac field, extend these results to maximally symmetric black holes and comment on the applicability of our results to establish the stability with respect to other classical fields.

Orbital dynamics of the gravitational field of stringy black holes

2014 ◽  
Vol 29 (29) ◽  
pp. 1450144 ◽  
Author(s):  
Yu Zhang ◽  
Jin-Ling Geng ◽  
En-Kun Li
Keyword(s):  
Black Holes ◽  
Angular Momentum ◽  
Gravitational Field ◽  
Phase Plane ◽  
Equations Of Motion ◽  
Orbital Dynamics ◽  
Phase Plane Analysis ◽  
Test Particles ◽  
Stable Circular Orbit ◽  
The Stability

In this paper, we study the orbital dynamics of the gravitational field of stringy black holes by analyzing the effective potential and the phase plane diagram. By solving the equation of Lagrangian, the general relativistic equations of motion in the gravitational field of stringy black holes are given. It is easy to find that the motion of test particles depends on the energy and angular momentum of the test particles. Using the phase plane analysis method and combining the conditions of the stability, we discuss different types of the test particles' orbits in the gravitational field of stringy black holes. We get the innermost stable circular orbit which occurs at r min = 5.47422 and when the angular momentum b ≤ 4.3887 the test particles will fall into the black hole.

scholarly journals Geodesic Effect Near an Elliptical Orbit

2012 ◽  
Vol 2012 ◽  
pp. 1-8
Author(s):  
Alina-Daniela Vîlcu
Keyword(s):  
Gravitational Field ◽  
Elliptical Orbit ◽  
Newtonian Mechanics ◽  
The Sun ◽  
Classical Approach ◽  
De Sitter ◽  
Lagrange Equations ◽  
The Earth ◽  
Elliptical Motion

Using a differential geometric treatment, we analytically derived the expression for De Sitter (geodesic) precession in the elliptical motion of the Earth through the gravitational field of the Sun with Schwarzschild's metric. The expression obtained in this paper in a simple way, using a classical approach, agrees with that given in B. M. Barker and R. F. O'Connell (1970, 1975) in a different setting, using the tools of Newtonian mechanics and the Euler-Lagrange equations.

Thermodynamic geometry of charged dilaton black holes in AdS spaces

2016 ◽  
Vol 94 (10) ◽  
pp. 1045-1053 ◽  
Author(s):  
Ahmad Sheykhi ◽  
Seyed Hossein Hendi ◽  
Fatemeh Naeimipour ◽  
Shahram Panahiyan ◽  
Behzad Eslam Panah
Keyword(s):  
Black Holes ◽  
Ricci Scalar ◽  
Thermodynamic Quantities ◽  
Geometrical Approach ◽  
De Sitter ◽  
Ads Black Holes ◽  
Divergence Points ◽  
The Stability ◽  
Thermodynamical Behavior ◽  
Dilaton Black Holes

It was shown that with the combination of three Liouville-type dilaton potentials, one can derive dilaton black holes in the background of anti-de-Sitter (AdS) spaces. In this paper, we further extend the study on the dilaton AdS black holes by investigating their thermodynamic instability through a geometry approach. First, we review thermodynamic quantities of the solutions and check the validity of the first law of thermodynamics. Then, we investigate phase transitions and stability of the solutions. In particular, we disclose the effects of the dilaton field on the stability of the black holes. We also employ the geometrical approach toward thermodynamical behavior of the system and find that the divergencies in the Ricci scalar coincide with roots and divergencies in the heat capacity. We find that the behavior of the Ricci scalar around divergence points depends on the type of the phase transition.

scholarly journals Phase Transition and Entropy Force between Two Horizons in (n+2)-Dimensional de Sitter Space

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Yang Zhang ◽  
Wen-qi Wang ◽  
Yu-bo Ma ◽  
Jun Wang
Keyword(s):  
Phase Transition ◽  
Black Holes ◽  
Physical Mechanism ◽  
De Sitter Space ◽  
Space Time ◽  
Thermodynamic Quantities ◽  
De Sitter ◽  
Time Dimension ◽  
Cosmic Expansion

In this paper, the effect of the space-time dimension on effective thermodynamic quantities in (n+2)-dimensional Reissner-Nordstrom-de Sitter space has been studied. Based on derived effective thermodynamic quantities, conditions for the phase transition are obtained. The result shows that the accelerating cosmic expansion can be attained by the entropy force arisen from the interaction between horizons of black holes and our universe, which provides a possible way to explain the physical mechanism for the accelerating cosmic expansion.

scholarly journals Exact Solutions in Poincaré Gauge Gravity Theory

Universe ◽  
2019 ◽  
Vol 5 (5) ◽  
pp. 127 ◽  
Author(s):  
Yuri N. Obukhov
Keyword(s):  
Gravitational Field ◽  
Gravity Models ◽  
Field Potentials ◽  
De Sitter ◽  
Field Equations ◽  
Yang Mills ◽  
Gravitational Field Equations ◽  
Poincaré Symmetry ◽  
Gauge Gravity ◽  
Vacuum Solutions

In the framework of the gauge theory based on the Poincaré symmetry group, the gravitational field is described in terms of the coframe and the local Lorentz connection. Considered as gauge field potentials, they give rise to the corresponding field strength which are naturally identified with the torsion and the curvature on the Riemann–Cartan spacetime. We study the class of quadratic Poincaré gauge gravity models with the most general Yang–Mills type Lagrangian which contains all possible parity-even and parity-odd invariants built from the torsion and the curvature. Exact vacuum solutions of the gravitational field equations are constructed as a certain deformation of de Sitter geometry. They are black holes with nontrivial torsion.

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