scholarly journals TRAVERSABLE WORMHOLES IN A STRING CLOUD

2008 ◽  
Vol 17 (08) ◽  
pp. 1179-1196 ◽  
Author(s):  
MARTÍN G. RICHARTE ◽  
CLAUDIO SIMEONE
Keyword(s):  
Thin Shell ◽  
Dimensional Space ◽  
Space Time ◽  
Exotic Matter ◽  
Spherically Symmetric ◽  
Related Model ◽  
Traversable Wormholes ◽  
Dimensional Space Time ◽  
Thin Shell Wormholes ◽  
The Stability

We study spherically symmetric thin shell wormholes in a string cloud background in (3 + 1)-dimensional space–time. The amount of exotic matter required for the construction, the traversability and the stability of such wormholes under radial perturbations are analyzed as functions of the parameters of the model. In addition, in the appendices a nonperturbative approach to the dynamics and a possible extension of the analysis to a related model are briefly discussed.

Dynamics of thin-shell wormholes with different cosmological models

2017 ◽  
Vol 26 (05) ◽  
pp. 1741007 ◽  
Author(s):  
Muhammad Sharif ◽  
Saadia Mumtaz
Keyword(s):  
Equation Of State ◽  
Electric Charge ◽  
General Equation ◽  
Thin Shell ◽  
Cosmological Models ◽  
Exotic Matter ◽  
Linear Perturbation ◽  
Stability Regions ◽  
Thin Shell Wormholes ◽  
The Stability

This work is devoted to investigate the stability of thin-shell wormholes in Einstein–Hoffmann–Born–Infeld electrodynamics. We also study the attractive and repulsive characteristics of these configurations. A general equation-of-state is considered in the form of linear perturbation which explores the stability of the respective wormhole solutions. We assume Chaplygin, linear and logarithmic gas models to study exotic matter at thin-shell and evaluate stability regions for different values of the involved parameters. It is concluded that the Hoffmann–Born–Infeld parameter and electric charge enhance the stability regions.

Charged thin-shell wormholes with quintessence effects

2021 ◽  
Vol 36 (26) ◽  
Author(s):  
Saadia Mumtaz
Keyword(s):  
Thin Shell ◽  
Chaplygin Gas ◽  
Exotic Matter ◽  
Stability Regions ◽  
Thin Shell Wormholes ◽  
Theoretical Construction ◽  
The Stability ◽  
Effective Component

This work studies the theoretical construction of charged quintessence thin-shell wormholes using Israel thin-shell approach. The stability of these wormhole solutions is investigated by taking linear, logarithmic and Chaplygin gas models as a constituent of exotic matter at thin-shell. The presence of wormhole stability regions particularly relies on the physically justifiable values of charge and quintessence parameter. It is noted that the increasing value of charge seems as an effective component for stable regions while the rise in negativity of the quintessence parameter gives more stable wormhole configurations.

NATURE OF THE SINGULARITIES IN HIGHER-DIMENSIONAL HUSAIN SPACE–TIME

2006 ◽  
Vol 15 (09) ◽  
pp. 1359-1371 ◽  
Author(s):  
K. D. PATIL ◽  
S. S. ZADE
Keyword(s):  
Gravitational Collapse ◽  
Dimensional Space ◽  
Higher Dimensions ◽  
Cosmic Censorship ◽  
Space Time ◽  
Spherically Symmetric ◽  
Naked Singularities ◽  
Higher Dimensional ◽  
Dimensional Space Time ◽  
Cosmic Censorship Hypothesis

We generalize the earlier studies on the spherically symmetric gravitational collapse in four-dimensional space–time to higher dimensions. It is found that the central singularities may be naked in higher dimensions but depend sensitively on the choices of the parameters. These naked singularities are found to be gravitationally strong that violate the cosmic censorship hypothesis.

scholarly journals No stable static spherically symmetric wormholes in Horndeski theory

2018 ◽  
Vol 191 ◽  
pp. 07012
Author(s):  
Oleg Evseev ◽  
Oleg Melichev
Keyword(s):  
Scalar Field ◽  
General Theory ◽  
Dimensional Space ◽  
Space Time ◽  
Second Order ◽  
Spherically Symmetric ◽  
Field Equations ◽  
Asymptotically Flat ◽  
Dimensional Space Time

We consider the most general theory of a single scalar field with the second order field equations, the Horndeski theory, in four-dimensional space-time. We show that static, spherically symmetric, asymptotically flat, Lorentzian wormholes are unstable in this theory.

scholarly journals Kaluza–Klein reduction and Bergmann–Wagoner bi-scalar general action of scalar–tensor gravity

2015 ◽  
Vol 12 (10) ◽  
pp. 1550106 ◽  
Author(s):  
Kazuharu Bamba ◽  
Davood Momeni ◽  
Ratbay Myrzakulov
Keyword(s):  
Dimensional Reduction ◽  
Dimensional Space ◽  
Space Time ◽  
De Sitter ◽  
Higher Dimensional Space Time ◽  
Higher Dimensional ◽  
Dimensional Space Time ◽  
General Action ◽  
The Stability ◽  
Kaluza Klein

We examine the Kaluza–Klein (KK) dimensional reduction from higher dimensional space-time and the properties of the resultant Bergmann–Wagoner general action of scalar–tensor theories. With the analysis of the perturbations, we also investigate the stability of the anti-de Sitter (AdS) space-time in the (D ∈ 𝒩)-dimensional Einstein gravity with the negative cosmological constant. Furthermore, we derive the conditions for the dimensional reduction to successfully be executed and present the KK compactification mechanism.

NO-BOUNDARY WAVE FUNCTION IN A HIGHER-DIMENSIONAL SPHERICALLY SYMMETRIC MICROSUPERSPACE MODEL

1992 ◽  
Vol 07 (08) ◽  
pp. 653-658 ◽  
Author(s):  
SUBENOY CHAKRABORTY
Keyword(s):  
Wave Function ◽  
Dimensional Space ◽  
Space Time ◽  
Functional Integral ◽  
Steepest Descent ◽  
Spherically Symmetric ◽  
Higher Dimensional ◽  
Dimensional Space Time ◽  
Method Of Steepest Descent

The wave function following the Hartle-Hawking (HH) no-boundary proposal is evaluated in five-dimensional space-time with topology of the four space S1×S3, generalizing the concept of microsuperspace. The functional integral in the expression for the wave function is simplified to an ordinary integration of one variable and is evaluated by the method of steepest-descent.

Thin-shell wormholes in rainbow gravity

2018 ◽  
Vol 33 (09) ◽  
pp. 1850049 ◽  
Author(s):  
Z. Amirabi ◽  
M. Halilsoy ◽  
S. Habib Mazharimousavi
Keyword(s):  
General Relativity ◽  
Thin Shell ◽  
Planck Scale ◽  
High Energy ◽  
Exotic Matter ◽  
Thin Shell Wormholes ◽  
The Stability ◽  
Planck Energy ◽  
High Energy Particles ◽  
Modified Theory

At the Planck scale of length [Formula: see text] m where the energy is comparable with the Planck energy, the quantum gravity corrections to the classical background spacetime results in gravity’s rainbow or rainbow gravity. In this modified theory of gravity, geometry depends on the energy of the test particle used to probe the spacetime, such that in the low energy limit, it yields the standard general relativity. In this work, we study the thin-shell wormholes in the spherically symmetric rainbow gravity. We find the corresponding properties in terms of the rainbow functions which are essential in the rainbow gravity and the stability of such thin-shell wormholes are investigated. Particularly, it will be shown that there are exact solutions in which high energy particles crossing the throat will encounter less amount of total exotic matter. This may be used as an advantage over general relativity to reduce the amount of exotic matter.

scholarly journals Stable Dyonic Thin-Shell Wormholes in Low-Energy String Theory

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Ali Övgün ◽  
Kimet Jusufi
Keyword(s):  
Electric Charge ◽  
Thin Shell ◽  
Magnetic Charge ◽  
State Parameter ◽  
Stability Domain ◽  
Chaplygin Gas ◽  
Space Time ◽  
Exotic Matter ◽  
The Stability ◽  
Parameter Values

Considerable attention has been devoted to the wormhole physics in the past 30 years by exploring the possibilities of finding traversable wormholes without the need for exotic matter. In particular, the thin-shell wormhole formalism has been widely investigated by exploiting the cut-and-paste technique to merge two space-time regions and to research the stability of these wormholes developed by Visser. This method helps us to minimize the amount of the exotic matter. In this paper, we construct a four-dimensional, spherically symmetric, dyonic thin-shell wormhole with electric charge Q, magnetic charge P, and dilaton charge Σ, in the context of Einstein-Maxwell-dilaton theory. We have applied Darmois-Israel formalism and the cut-and-paste method by joining together two identical space-time solutions. We carry out the dyonic thin-shell wormhole stability analyses by using a linear barotropic gas, Chaplygin gas, and logarithmic gas for the exotic matter. It is shown that, by choosing suitable parameter values as well as equation of state parameter, under specific conditions, we obtain a stable dyonic thin-shell wormhole solution. Finally, we argue that the stability domain of the dyonic thin-shell wormhole can be increased in terms of electric charge, magnetic charge, and dilaton charge.

scholarly journals General relativistic results for a galactic disc in a multidimensional space-time

2006 ◽  
Vol 2 (S238) ◽  
pp. 343-344
Author(s):  
Carlos H. Coimbra-Araújo ◽  
Patricio S. Letelier
Keyword(s):  
Dimensional Space ◽  
Space Time ◽  
Multidimensional Space ◽  
Galactic Disc ◽  
Relativistic Model ◽  
Dimensional Space Time ◽  
General Relativistic ◽  
The Stability ◽  
Circular Geodesic

AbstractWe construct an exact and simple general relativistic model to describe a galactic disc based on a Schwarzschild disc immersed in a six dimensional space-time. The stability of this configuration is studied and we present results for the calculation of circular geodesic orbits.

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