Electromagnetic-field equations in the six-dimensional space-time R6

1984 ◽  
Vol 40 (4) ◽  
pp. 121-125 ◽  
Author(s):  
M. T. Teli ◽  
D. Palaskar
2017 ◽  
Vol 45 ◽  
pp. 1760005 ◽  
Author(s):  
Ivan Morales ◽  
Bruno Neves ◽  
Zui Oporto ◽  
Olivier Piguet

We propose a gravitation theory in 4 dimensional space-time obtained by compacting to 4 dimensions the five dimensional topological Chern-Simons theory with the gauge group SO(1,5) or SO(2,4) – the de Sitter or anti-de Sitter group of 5-dimensional space-time. In the resulting theory, torsion, which is solution of the field equations as in any gravitation theory in the first order formalism, is not necessarily zero. However, a cosmological solution with zero torsion exists, which reproduces the Lambda-CDM cosmological solution of General Relativity. A realistic solution with spherical symmetry is also obtained.


2004 ◽  
Vol 19 (29) ◽  
pp. 5043-5050 ◽  
Author(s):  
YONGGE MA ◽  
JUN WU

A free test particle in five-dimensional Kaluza–Klein space–time will show its electricity in the reduced four-dimensional space–time when it moves along the fifth dimension. In the light of this observation, we study the coupling of a five-dimensional dust field with the Kaluza–Klein gravity. It turns out that the dust field can curve the five-dimensional space–time in such a way that it provides exactly the source of the electromagnetic field in the four-dimensional space–time after the dimensional reduction.


2005 ◽  
Vol 20 (05) ◽  
pp. 993-999 ◽  
Author(s):  
F. RAHAMAN ◽  
P. GHOSH ◽  
M. KALAM ◽  
S. MANDAL

We study the gravitational properties of a global monopole in (D=d+2)-dimensional space–time in the presence of electromagnetic field.


2001 ◽  
Vol 16 (11) ◽  
pp. 685-692 ◽  
Author(s):  
G. ZET ◽  
V. MANTA ◽  
C. BANDAC

A model of SU(2) gauge theory is constructed in terms of local gauge-invariant variables defined over a four-dimensional space–time endowed with axial symmetry. A metric tensor gμν is defined starting with the components [Formula: see text] of the strength tensor and its dual [Formula: see text]. The components gμν are interpreted as new local gauge-invariant variables. Imposing the condition that the new metric coincides with the initial metric we obtain the field equations for the considered ansatz. We obtain the same field equations using the condition of self-duality. It is concluded that the self-dual variables are compatible with the axial symmetry of the space–time. A family of analytical solutions of the gauge field equations is also obtained. The solutions have the confining properties. All the calculations are performed using the GRTensorII computer algebra package, running on the MapleV platform.


1989 ◽  
Vol 04 (10) ◽  
pp. 2627-2652 ◽  
Author(s):  
V.V. NESTERENKO

The classical and quantum dynamics of an open bosonic string propagating in the D-dimensional space-time in the presence of a background electromagnetic field is investigated. An important point in this consideration is the use of the generalized light-like gauge. There are considered the two types of strings: the neutral strings with charges at their ends obeying the condition q1+q2=0 and the charged strings having a net charge q1+q2≠0. The consistency of the theory demands that the background electric field does not exceed its critical value. The distance between the mass levels of the neutral open string decreases (1−e2) times in comparison with the free string where e is the dimensionless strength of the electric field. The magnetic field does not affect this distance. It is shown that at a classical level, the squared mass of the neutral open string has a tachyonic contribution due to the motion of the string as a whole in transverse directions. The tachyonic term disappears if one considers, instead of M2, the string energy in a special reference frame where the projection of the total canonical momentum of the string onto the electric field vanishes. The contributions due to zero point fluctuations to the energy spectrum of the neutral string and to the Virasoro operators in the theory of charged string are found. It is shown that the constraint on the strength of an external electric field is absent when the open bosonic string is placed in an external electromagnetic field of a special configuration. In the case of four-dimensional space-time, it corresponds to the electric and magnetic fields which are equal and perpendicular to each other (isotropic configuration). The external electromagnetic field does not act on the fermionic variables of the spinning string.


2018 ◽  
Vol 191 ◽  
pp. 07012
Author(s):  
Oleg Evseev ◽  
Oleg Melichev

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.


2002 ◽  
Vol 17 (20) ◽  
pp. 2777-2777
Author(s):  
P. TEYSSANDIER

Presently, there exists some renewed interest in time varying speed of light theories as possible solutions of the major cosmological problems1. It is often believed that the local Lorentzian invariance is broken if the speed of light in a vacuum is not a constant. We point out that this belief is not necessarily founded and that a variable speed of light is perfectly consistent with general relativity under the assumption of non-minimal coupling between electromagnetism and curvature. Two kinds of arguments may be invoked in favour of such an assumption. First, a theorem due to Horndeski2 shows that in a four-dimensional space-time the Einstein-Maxwell field equations are not the only second-order vector potential field equations which stem from a Lagrangian scalar density, are consistent with the charge conservation and reduce to Maxwell's equations in a flat space-time (see also3). Second, according to QED4,5, vacuum polarization induces tidal gravitational effects which imply that photons propagating in a curved space-time have velocities exceeding the value of the "Lorentzian structural constant" c. The modified electromagnetic field equations given by Horndeski2 are studied here in the geometrical optics limit. Considering the case of Friedmann-Robertson-Walker cosmological models, we find the value of the speed of light as a function of the energetic content of the universe. We deduce from this result a new equation of state for a photon gas and we discuss the consequences of this equation on the evolution of the scale factor during the radiation-dominated era.


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