Searcharxiv⌕ Search

arXiv subjects

S. S. Xulu

Publications and source records attributed to S. S. Xulu.

14 recordsLinked to original sources

Effective gravitational mass of the Ayón-Beato and Garc\'ıa metric

In this paper, we calculate the effective gravitational mass of Ayón-Beato and Garc\'ıa regular (non-singular) static spherically symmetric asymptotically Minkowskian metric that is a solution to Einstein's equations coupled with a nonlinear electromagnetic field. The effective gravitational mass is negative, zero, or positive that depends on the ratio of magnitude of electric charge to the ADM mass and the ratio of the radial distance to the ADM mass. As expected, at large value of radial distance, our result gives effective gravitational mass of the Reissner-Nordström metric.

gr-qc↗

Energy and momentum of Bianchi Type VI_h Universes

We obtain the energy and momentum of the Bianchi type VI_h universes using different prescriptions for the energy-momentum complexes in the framework of general relativity. The energy and momentum of the Bianchi VI_h universe are found to be zero for the parameter h = -1 of the metric. The vanishing of these results support the conjecture of Tryon that Universe must have a zero net value for all conserved quantities.This also supports the work of Nathan Rosen with the Robertson-Walker metric. Moreover, it raises an interesting question: "Why h=-1 case is so special?"

gr-qc↗

Einstein energy-momentum complex for a phantom black hole metric

In this paper we calculate the energy distribution E(r) associated with a static spherically symmetric non-singular phantom black hole metric in Einstein's prescription in general relativity. As required for Einstein energy-momentum complex, we perform calculations in quasi-Cartesian coordinates. We also calculate momentum components and get zero values as expected from the geometry of the metric.

gr-qc↗

Bergmann-Thomson energy-momentum complex for solutions more general than the Kerr-Schild class

In a very well-known paper, Virbhadra's research group proved that the Weinberg, Papapetrou, Landau and Lifshitz, and Einstein energy-momentum complexes ``coincide'' for all metrics of Kerr-Schild class. A few years later, Virbhadra clarified that this ``coincidence'' in fact holds for metrics more general than the Kerr-Schild class. In the present paper, this study is extended for the Bergmann-Thomson complex and it is proved that this complex also ``coincides'' with those complexes for a more general than the Kerr-Schild class metric.

gr-qc↗

Energy distribution in Kerr-Newman space-time in Bergmann-Thomson formulation

We obtain the energy distribution in the Kerr-Newman metric with the help of Bergmann-Thomson energy-momentum complex. We find that the energy-momentum definitions prescribed by Einstein, Landau-Lifshitz, Papapetrou, Weinberg, and Bergmann-Thomson give the same and acceptable result and also support the {\em Cooperstock Hypothesis} for energy localization in general relativity. The repulsive effect due to the electric charge and rotation parameters of the metric is also reflected from the energy distribution expression.

hep-th↗

The Energy-Momentum Problem in General Relativity

Energy-momentum is an important conserved quantity whose definition has been a focus of many investigations in general relativity. Unfortunately, there is still no generally accepted definition of energy and momentum in general relativity. Attempts aimed at finding a quantity for describing distribution of energy-momentum due to matter, non-gravitational and gravitational fields resulted in various energy-momentum complexes whose physical meaning have been questioned. The problems associated with energy-momentum complexes resulted in some researchers even abandoning the concept of energy-momentum localization in favour of the alternative concept of quasi-localization. However, quasi-local masses have their inadequacies, while the remarkable work of Virbhadra and some others, and recent results of Cooperstock and Chang {\it et al.} have revived an interest in various energy-momentum complexes. Hence in this work we use energy-momentum complexes to obtain the energy distributions in various space-times. We elaborate on the problem of energy localization in general relativity and use energy-momentum prescriptions of Einstein, Landau and Lifshitz, Papapetrou, Weinberg, and Møller to investigate energy distributions in various space-times. It is shown that several of these energy-momentum complexes give the same and acceptable results for a given space-time. This shows the importance of these energy-momentum complexes. Our results agree with Virbhadra's conclusion that the Einstein's energy-momentum complex is still the best tool for obtaining energy distribution in a given space-time. The Cooperstock hypothesis for energy localization in GR is also supported.

hep-th↗

Energy distribution in the dyadosphere of a charged black hole

The event horizon of a charged black hole is, according to Ruffini\cite{Ruffini} and Preparata \emph{et al.}\cite{PreparataEtAl}, surrounded by a special region called the \emph{dyadosphere} where the electromagnetic field exceeds the Euler-Heisenberg critical value for electron-positron pair production. We obtain the energy distribution in the dyadosphere region for a Reissner-Nordström black hole. We find that the energy-momentum prescriptions of Einstein, Landau-Lifshitz, Papapetrou, and Weinberg give the same and acceptable energy distribution.

gr-qc↗

Møller energy of the nonstatic spherically symmetric metrics

The energy distribution in the most general nonstatic spherically symmetric space-time is obtained using Møller's energy-momentum complex. This result is compared with the energy expression obtained by using the energy-momentum complex of Einstein. Some examples of energy distributions in different prescriptions are discussed.

gr-qc↗

Møller Energy for the Kerr-Newman metric

The energy distribution in the Kerr-Newman space-time is computed using the Møller energy-momentum complex. This agrees with the Komar mass for this space-time obtained by Cohen and de Felice. These results support the Cooperstock hypothesis.

gr-qc↗

Energy Associated with Schwarzschild Black Hole in a Magnetic Universe

In this paper we obtain the energy distribution associated with the Ernst space-time (geometry describing Schwarzschild black hole in Melvin's magnetic universe) in Einstein's prescription. The first term is the rest-mass energy of the Schwarzschild black hole, the second term is the classical value for the energy of the uniform magnetic field and the remaining terms in the expression are due to the general relativistic effect. The presence of the magnetic field is found to increase the energy of the system.

gr-qc↗

Energy Distribution in Melvin's Magnetic Universe

We use the energy-momentum complexes of Landau and Lifshitz and Papapetrou to obtain the energy distribution in Melvin's magnetic universe. For this space-time we find that these definitions of energy give the same and convincing results. The energy distribution obtained here is the same as we obtained earlier for the same space-time using the energy-momentum complex of Einstein. These results uphold the usefulness of the energy-momentum complexes.

gr-qc↗

Total Energy of the Bianchi Type I Universes

Using the symmetric energy-momentum complexes of Landau and Lifshitz, Papapetrou, and Weinberg we obtain the energy of the universe in anisotropic Bianchi type I cosmological models . The energy (due to matter plus field) is found to be zero and this agrees with a previous result of Banerjee and Sen who investigated this problem using the Einstein energy-momentum complex. Our result supports the importance of the energy-momentum complexes and contradicts the prevailing ``folklore'' that different energy-momentum complexes could give different and hence unacceptable energy distribution in a given space-time. The result that the total energy of the universe in these models is zero supports the viewpoint of Tryon. Rosen computed the total energy of the closed homogeneous isotropic universe and found that to be zero, which agrees with the studies of Tryon.

gr-qc↗

Energy distribution of charged dilaton black holes

Chamorro and Virbhadra studied, using the energy-momentum complex of Einstein, the energy distribution associated with static spherically symmetric charged dilaton black holes for an arbitrary value of the coupling parameter $γ$ which controls the strength of the dilaton to the Maxwell field. We study the same in Tolman's prescription and get the same result as obtained by Chamorro and Virbhadra. The energy distribution of charged dilaton black holes depends on the value of $γ$ and the total energy is independent of this parameter.

hep-th↗

Tolman's energy of a stringy charged black hole

Virbhadra and Parikh studied the energy distribution associated with stringy charged black hole in Einstein's prescription. We study the same using Tolman's energy-momentum complex and get the same result as obtained by Virbhadra and Parikh. The entire energy is confined inside the black hole.

gr-qc↗