scholarly journals Magnetic brane of cubic quasi-topological gravity in the presence of Maxwell and Born–Infeld electromagnetic field

2018 ◽  
Vol 96 (11) ◽  
pp. 1209-1215 ◽  
Author(s):  
M. Ghanaatian ◽  
A. Bazrafshan ◽  
S. Taghipoor ◽  
R. Tawoosi
Keyword(s):  
Electromagnetic Field ◽  
Maxwell Field ◽  
Curvature Singularity ◽  
Deficit Angle ◽  
Topological Gravity ◽  
Metric Function

The main purpose of the present paper is analyzing magnetic brane solutions of cubic quasi-topological gravity in the presence of a linear electromagnetic Maxwell field and a nonlinear electromagnetic Born–Infeld field. We show that the mentioned magnetic solutions have no curvature singularity and also no horizons, but we observe that there is a conic geometry with a related deficit angle. We obtain the metric function and deficit angle and consider their behavior. We show that the attributes of our solution are dependent on cubic quasi-topological coefficient and the Gauss–Bonnet parameter.

scholarly journals GENERALIZED EINSTEIN–MAXWELL FIELD EQUATIONS IN THE PALATINI FORMALISM

2013 ◽  
Vol 22 (04) ◽  
pp. 1350017 ◽  
Author(s):  
GINÉS R. PÉREZ TERUEL
Keyword(s):  
Electromagnetic Field ◽  
Algebraic Equation ◽  
Ricci Tensor ◽  
Maxwell Equations ◽  
Natural Generalization ◽  
New Method ◽  
Maxwell Field ◽  
Field Equations ◽  
Palatini Formalism

We derive a new set of field equations within the framework of the Palatini formalism. These equations are a natural generalization of the Einstein–Maxwell equations which arise by adding a function [Formula: see text], with [Formula: see text] to the Palatini Lagrangian f(R, Q). The result we obtain can be viewed as the coupling of gravity with a nonlinear extension of the electromagnetic field. In addition, a new method is introduced to solve the algebraic equation associated to the Ricci tensor.

scholarly journals BORN–INFELD COSMOLOGIES

2000 ◽  
Vol 15 (27) ◽  
pp. 4341-4353 ◽  
Author(s):  
RICARDO GARCÍA-SALCEDO ◽  
NORA BRETÓN
Keyword(s):  
Electromagnetic Field ◽  
Early Universe ◽  
Big Bang ◽  
Linear Case ◽  
Conformal Metric ◽  
Curvature Invariants ◽  
Metric Function ◽  
Big Bang Singularity

We present a model for an inhomogeneous and anisotropic early universe filled with a nonlinear electromagnetic field of Born–Infeld (BI) type. The effects of the BI field are compared with the linear case (Maxwell). Since the curvature invariants are well behaved then we conjecture that our model does not present an initial big bang singularity. The existence of the BI field modifies the curvature invariants at t=0 as well as sets bounds on the amplitude of the conformal metric function.

scholarly journals The Spacetime Surrounding Superconducting Cosmic Strings

1988 ◽  
Vol 130 ◽  
pp. 564-564
Author(s):  
T. M. Helliwell ◽  
D. A. Konkowski
Keyword(s):  
Electromagnetic Field ◽  
Stress Tensor ◽  
Linear Approximation ◽  
Mass Density ◽  
Cosmic Strings ◽  
External Electromagnetic Field ◽  
Cylindrical Coordinates ◽  
Linear Mass ◽  
Deficit Angle ◽  
Image Position

In 1981, A. Vilenkin derived the stress tensor for a straight nonconducting cosmic string of linear mass density μ oriented in the z-direction; it is given by Tμν = μdiag(1,0,0,1) δ (x) δ (y). He also showed that in linear approximation the resulting exterior spacetime is flat but conical, with deficit angle 8πGμ. Subsequently it was shown that even the exact spacetime is flat but conical. Recently E. Copeland, M. Hindmarsh, and N. Turok have derived the stress tensor for a straight current-carrying string, where j is proportional to the current. We have used this stress tensor, together with the stress tensor of the external electromagnetic field caused by the current, to find the external spacetime of a conducting string in linear approximation. In cylindrical coordinates, the metric may be written where h00 = 4GI2ln2r/r0 + 8Gμj2lnr/r0 = h33 + 8GI2lnr/r0, and a = 1–4Gμ–2GI2. Here r0 is the string radius and I is the electric current, related to j as described in reference 4. The linear approximation is valid as long as h0 0 and h3 3 are small compared with unity, which restricts the range of r. The (r, φ) subspace is flat but conical, with deficit angle 8πG(μ + I2/2). The spacetime reduces to that found by Vilenkin if j and I go to zero. Efforts are currently underway to find an exact exterior solution, which would apply for arbitrary values of r.

scholarly journals NONLINEAR CHARGED BLACK HOLES IN AdS QUASI-TOPOLOGICAL GRAVITY

2013 ◽  
Vol 22 (13) ◽  
pp. 1350076 ◽  
Author(s):  
MOHAMMAD GHANAATIAN ◽  
AFSANEH BAZRAFSHAN
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Electromagnetic Field ◽  
Fourth Order ◽  
Naked Singularity ◽  
Charged Black Holes ◽  
Topological Parameters ◽  
Mass Temperature ◽  
Topological Gravity ◽  
The Stability

In this paper, we present the static charged solutions of quartic quasi-topological gravity in the presence of a nonlinear electromagnetic field. Two branches of these solutions present black holes with one or two horizons or a naked singularity depending on the charge and mass of the black hole. The entropy of the charged black holes of fourth-order quasi-topological gravity through the use of Wald formula is computed and the mass, temperature and the charge of these black holes are found as well. We show that black holes with spherical, flat and hyperbolical horizon in quasi-topological gravity are stable for any allowed quasi-topological parameters. We also investigate the stability of nonlinear charged black holes.

The Maxwell field, its adjoint field and the ‘conjugate’field in anisotropic absorbing media

1975 ◽  
Vol 13 (2) ◽  
pp. 299-316 ◽  
Author(s):  
Kurt Suchy ◽  
Colman Altman
Keyword(s):  
Electromagnetic Field ◽  
Differential Operator ◽  
Maxwell’S Equations ◽  
Maxwell's Equations ◽  
Poynting Vector ◽  
Maxwell Field ◽  
Absorbing Medium ◽  
Maxwell Operator ◽  
Physical Information ◽  
Absorbing Media

In absorbing media, where Maxwell's equations are not seif-adjoint, the adjoint field is introduced via the differential operator adjoint to the Maxwell operator. The concomitant vector can be made equal to the time averaged Poynting vector at a boundary with a non-absorbing medium. In general, the adjoint field represents an electromagnetic field in a medium other than the absorbing medium under consideration. To draw conclusions about the latter, a [conjugate field] in this medium is defined, using a conjugating transformation of the Maxwell operator and field. Relations between the conjugate and adjoint fields are established, allowing one to gather physical information about the first absorbing medium from the adjoint field.

Complexity factor for charged dissipative dynamical system

2020 ◽  
Vol 35 (28) ◽  
pp. 2050231
Author(s):  
M. Sharif ◽  
Saher Tariq
Keyword(s):  
Dynamical System ◽  
Electromagnetic Field ◽  
Maxwell Field ◽  
Anisotropic Fluid ◽  
Field Equations ◽  
Spherical System ◽  
Structure Scalars ◽  
Dissipative Dynamical System ◽  
The Stability ◽  
Dissipative Fluids

In this paper, we examine the complexity factor for a dynamical spherical system with dissipative charged anisotropic fluid. We evaluate the Einstein-Maxwell field equations and structure scalars using Bel’s approach which help to discuss the structure as well as evolution of a self-gravitating system. We measure the complexity factor for the pattern of evolution through the homologous condition and homogeneous expansion. We also analyze the stability of vanishing complexity condition for dissipative and non-dissipative fluids. It is found that the complexity as well as stability of the spherical system increases and decreases, respectively, under the effects of electromagnetic field.

scholarly journals On the force caused by a null Einstein-Maxwell field with the plane symmetry

2021 ◽  
Vol 2081 (1) ◽  
pp. 012033
Author(s):  
V N Timofeev
Keyword(s):  
Electromagnetic Field ◽  
Test Particle ◽  
Alternating Current ◽  
Space Time ◽  
Maxwell Field ◽  
Constant Current ◽  
Plane Symmetry ◽  
Null Electromagnetic Field ◽  
Current Flows

Abstract The article shows that a large flat platform with a constant current, which flows over its surface, accelerates time. It is also shown that if an alternating current flows along the surface of a flat platform while creating a null electromagnetic field then a force repelling from the platform acts on the test particle located near it. This force has no gravitational nature and arises as a result of the curvature of space-time by the electromagnetic field of a flat platform with an alternating current.

scholarly journals Wormhole Solutions in the Presence of Nonlinear Maxwell Field

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
S. H. Hendi
Keyword(s):  
Electromagnetic Field ◽  
Lower Bound ◽  
Maxwell Field ◽  
Nonlinear Electrodynamics ◽  
Radial Coordinate ◽  
Conserved Quantities ◽  
Static Solutions

In generalizing the Maxwell field to nonlinear electrodynamics, we look for the magnetic solutions. We consider a suitable real metric with a lower bound on the radial coordinate and investigate the properties of the solutions. We find that in order to have a finite electromagnetic field near the lower bound, we should replace the Born-Infeld theory with another nonlinear electrodynamics theory. Also, we use the cut-and-paste method to construct wormhole structure. We generalize the static solutions to rotating spacetime and obtain conserved quantities.

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