The effects of conformally invariant Maxwell source on the magnetic wormhole solutions in Gauss–Bonnet gravity

2011 ◽  
Vol 89 (3) ◽  
pp. 281-287 ◽  
Author(s):  
S. H. Hendi
Keyword(s):  
Electric Charge ◽  
Rotation Parameter ◽  
Energy Conditions ◽  
Conserved Quantities ◽  
Bonnet Gravity ◽  
Four Dimensions ◽  
Conformally Invariant ◽  
New Class ◽  
Traversable Wormholes ◽  
Higher Dimensional

In this paper we introduce a new class of nonsingular higher dimensional conformally invariant magnetic solutions that may be interpreted as traversable wormholes, which could be supported by matter not violating the weak energy conditions. The electromagnetic source is chosen in which the expression of the Maxwell field does not depend on the dimension and its value coincides with the Reissner–Nordström solution in four dimensions. We generalize this class of solutions to the case of rotating solutions and show that the rotating wormhole solutions have a net electric charge that is proportional to the magnitude of the rotation parameter, while the static wormhole has no net electric charge. Finally, we use the counterterm method and compute the conserved quantities of these spacetimes.

scholarly journals The averaged null energy conditions in even dimensional curved spacetimes from AdS/CFT duality

2020 ◽  
Vol 2020 (10) ◽  
Author(s):  
Norihiro Iizuka ◽  
Akihiro Ishibashi ◽  
Kengo Maeda
Keyword(s):  
Weight Function ◽  
Energy Condition ◽  
Null Energy Condition ◽  
Two Dimensions ◽  
Energy Conditions ◽  
Quantum Field Theories ◽  
Strongly Coupled ◽  
Four Dimensions ◽  
Conformally Invariant ◽  
Curved Spacetimes

Abstract We consider averaged null energy conditions (ANEC) for strongly coupled quantum field theories in even (two and four) dimensional curved spacetimes by applying the no-bulk-shortcut principle in the context of the AdS/CFT duality. In the same context but in odd-dimensions, the present authors previously derived a conformally invariant averaged null energy condition (CANEC), which is a version of the ANEC with a certain weight function for conformal invariance. In even-dimensions, however, one has to deal with gravitational conformal anomalies, which make relevant formulas much more complicated than the odd-dimensional case. In two-dimensions, we derive the ANEC by applying the no-bulk-shortcut principle. In four-dimensions, we derive an inequality which essentially provides the lower-bound for the ANEC with a weight function. For this purpose, and also to get some geometric insights into gravitational conformal anomalies, we express the stress-energy formulas in terms of geometric quantities such as the expansions of boundary null geodesics and a quasi-local mass of the boundary geometry. We argue when the lowest bound is achieved and also discuss when the averaged value of the null energy can be negative, considering a simple example of a spatially compact universe with wormhole throat.

scholarly journals Higher-dimensional inhomogeneous composite fluids: energy conditions

2021 ◽  
Vol 2021 (10) ◽  
Author(s):  
Byron P Brassel ◽  
Sunil D Maharaj ◽  
Rituparno Goswami
Keyword(s):  
Energy Conditions ◽  
Fluid Distribution ◽  
Shear Stresses ◽  
Type I ◽  
Type Ii ◽  
Four Dimensions ◽  
Higher Dimensional ◽  
Matter Fields ◽  
Inhomogeneous Composite ◽  
Type Ii Fluid

Abstract The energy conditions are studied, in the relativistic astrophysical setting, for higher-dimensional Hawking–Ellis Type I and Type II matter fields. The null, weak, dominant and strong energy conditions are investigated for a higher-dimensional inhomogeneous, composite fluid distribution consisting of anisotropy, shear stresses, non-vanishing viscosity as well as a null dust and null string energy density. These conditions are expressed as a system of six equations in the matter variables where the presence of the higher dimension $N$ is explicit. The form and structure of the energy conditions is influenced by the geometry of the $(N-2)$-sphere. The energy conditions for the higher-dimensional Type II fluid are also generated, and it is shown that under certain restrictions the conditions for a Type I fluid are regained. All previous treatments for four dimensions are contained in our work.

scholarly journals Magnetic String with a NonlinearU(1)Source

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
S. H. Hendi
Keyword(s):  
Asymptotic Behavior ◽  
Magnetic Fields ◽  
Electromagnetic Fields ◽  
Einstein Gravity ◽  
Rotation Parameter ◽  
Conserved Quantities ◽  
Curvature Singularity ◽  
Conic Singularity ◽  
Higher Dimensional ◽  
Rotation Parameters

Considering the Einstein gravity in the presence of Born-Infeld type electromagnetic fields, we introduce a class of 4-dimensional static horizonless solutions which produce longitudinal magnetic fields. Although these solutions do not have any curvature singularity and horizon, there exists a conic singularity. We investigate the effects of nonlinear electromagnetic fields on the properties of the solutions and find that the asymptotic behavior of the solutions is adS. Next, we generalize the static metric to the case of rotating solutions and find that the value of the electric charge depends on the rotation parameter. Furthermore, conserved quantities will be calculated through the use of the counterterm method. Finally, we extend four-dimensional magnetic solutions to higher dimensional solutions. We present higher dimensional rotating magnetic branes with maximum rotation parameters and obtain their conserved quantities.

scholarly journals Wormhole solutions in Rastall gravity theory

2019 ◽  
Vol 34 (12) ◽  
pp. 1950095 ◽  
Author(s):  
Shibaji Halder ◽  
Subhra Bhattacharya ◽  
Subenoy Chakraborty
Keyword(s):  
General Relativity ◽  
Gravity Theory ◽  
Energy Conditions ◽  
Minimal Coupling ◽  
Traversable Wormholes ◽  
Matter Tensor ◽  
Higher Dimensional ◽  
Dimensional Gravity ◽  
Tensor Part

This work looks for new wormhole solutions in the non-conservative Rastall gravity. Although Rastall gravity is considered to be a higher-dimensional gravity, the actual diversion from general relativity essentially happens due to a modification in the corresponding matter tensor part. Thus, it would be interesting to find out if such non-minimal coupling has any effect on the traversable wormholes and their corresponding energy conditions.

scholarly journals Traversable wormholes in Einsteinian cubic gravity

2019 ◽  
Vol 35 (06) ◽  
pp. 2050017 ◽  
Author(s):  
Mohammad Reza Mehdizadeh ◽  
Amir Hadi Ziaie
Keyword(s):  
Equation Of State ◽  
Gravitational Lensing ◽  
Energy Condition ◽  
Higher Order ◽  
Energy Conditions ◽  
Geodesic Motion ◽  
De Sitter ◽  
Asymptotically Flat ◽  
Traversable Wormholes ◽  
Standard Energy

In this work, we investigate wormhole configurations described by a constant redshift function in Einstein-Cubic gravity ( ECG ). We derive analytical wormhole geometries by assuming a particular equation of state ( EoS ) and investigate the possibility that these solutions satisfy the standard energy conditions. We introduce exact asymptotically flat and anti-de Sitter (AdS) spacetimes that admit traversable wormholes. These solutions are obtained by imposing suitable values for the parameters of the theory so that the resulted geometries satisfy the weak energy condition ( WEC ) in the vicinity of the throat, due to the presence of higher-order curvature terms. Moreover, we find that AdS solutions satisfy the WEC throughout the spacetime. A description of the geodesic motion of time-like and null particles is presented for the obtained wormhole solutions. Also, using gravitational lensing effects, observational features of the wormhole structure are discussed.

scholarly journals Traversable wormholes with exponential shape function in modified gravity and general relativity: A comparative study

2020 ◽  
Vol 29 (09) ◽  
pp. 2050068 ◽  
Author(s):  
Gauranga C. Samanta ◽  
Nisha Godani ◽  
Kazuharu Bamba
Keyword(s):  
General Relativity ◽  
Equation Of State ◽  
Comparative Study ◽  
Modified Gravity ◽  
Shape Function ◽  
Anisotropy Parameter ◽  
Energy Conditions ◽  
Traversable Wormholes

We have proposed a novel shape function on which the metric that models traversable wormholes is dependent. Using this shape function, the energy conditions, equation-of-state and anisotropy parameter are analyzed in [Formula: see text] gravity, [Formula: see text] gravity and general relativity. Furthermore, the consequences obtained with respect to these theories are compared. In addition, the existence of wormhole geometries is investigated.

CLASSICAL INSTABILITY OF THE EINSTEIN-GAUSS-BONNET GRAVITY THEORY WITH COMPACTIFIED HIGHER DIMENSIONS

1991 ◽  
Vol 06 (25) ◽  
pp. 4517-4555 ◽  
Author(s):  
LESZEK M. SOKOŁOWSKI ◽  
ZDZISŁAW A. GOLDA ◽  
MARCO LITTERIO ◽  
LUCA AMENDOLA
Keyword(s):  
Scalar Fields ◽  
Gravity Theory ◽  
Effective Theory ◽  
Internal Space ◽  
Bonnet Gravity ◽  
Four Dimensions ◽  
Effective Gravity ◽  
Tensor Theory ◽  
Exciting System ◽  
Bonnet Term

The energy spectrum and stability of the effective theory resulting from the Einstein-Gauss-Bonnet gravity theory with compactified internal space are investigated. The internal space can evolve in its volume and/or shape, giving rise to a system of scalar fields in the external space-time. The resulting scalar-tensor theory of gravity has physically unacceptable properties. First of all, the scalar fields’ energy is indefinite and unbounded from below, and thereby the gravitational and scalar fields form a self-exciting system. In contradistinction to the case of multidimensional Einstein gravity, this inherent instability of the effective theory cannot be removed by field redefinitions in the process of dimensional reduction (e.g. by a conformal rescaling of the metric in four dimensions, as is done in the former case). To get a viable effective gravity theory one should discard either the geometric scalar fields or the Gauss-Bonnet term from the Lagrangian of the multidimensional theory. It is argued that it is the Gauss-Bonnet term that should be discarded.

Charging effect on traversable wormholes in f(R) = R + αRm + βR−n gravity

2021 ◽  
pp. 2150144
Author(s):  
Nisha Godani
Keyword(s):  
Shape Function ◽  
Energy Conditions ◽  
Logarithmic Form ◽  
Traversable Wormholes ◽  
Charging Effect

In this paper, traversable wormholes have been studied in [Formula: see text] gravity, where [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] are constant. A simplest form of shape function and a logarithmic form of redshift function is considered to construct wormhole solutions. The range of parameters providing the wormhole solutions free from the matter violating the energy conditions is explored. Further, the effect of charge is analyzed on wormhole solutions.

scholarly journals Wormhole modeling in R2 gravity with linear trace term

2020 ◽  
Vol 35 (08) ◽  
pp. 2050045
Author(s):  
Nisha Godani ◽  
Gauranga C. Samanta
Keyword(s):  
General Relativity ◽  
General Theory ◽  
Significant Contribution ◽  
Shape Function ◽  
Exotic Matter ◽  
Geometric Configuration ◽  
Energy Conditions ◽  
Theory Of Relativity ◽  
General Theory Of Relativity ◽  
Traversable Wormholes

Morris and Thorne1 proposed traversable wormholes, hypothetical connecting tools, using the concept of Einstein’s general theory of relativity. In this paper, the modification of general relativity (in particular [Formula: see text] theory of gravity defined by Harko et al.2) is considered, to study the traversable wormhole solutions. The function [Formula: see text] is considered as [Formula: see text], where [Formula: see text] and [Formula: see text] are controlling parameters. The shape and redshift functions appearing in the metric of wormhole structure have significant contribution in the development of wormhole solutions. We have considered both variable and constant redshift functions with a logarithmic shape function. The energy conditions are examined, geometric configuration is analyzed and the radius of the throat is determined in order to have wormhole solutions in absence of exotic matter.

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