4,660 research outputs found
Energy Contents of Gravitational Waves in Teleparallel Gravity
The conserved quantities, that are, gravitational energy-momentum and its
relevant quantities are investigated for cylindrical and spherical
gravitational waves in the framework of teleparallel equivalent of General
Relativity using the Hamiltonian approach. For both cylindrical and spherical
gravitational waves, we obtain definite energy and constant momentum. The
constant momentum shows consistency with the results available in General
Relativity and teleparallel gravity. The angular momentum for cylindrical and
spherical gravitational waves also turn out to be constant. Further, we
evaluate their gravitational energy-momentum fluxes and gravitational pressure.Comment: 14 pages, accepted for publication in Mod. Phys. Lett.
Classification of Static Plane Symmetric Spacetimes according to their Matter Collineations
In this paper we classify static plane symmetric spacetimes according to
their matter collineations. These have been studied for both cases when the
energy-momentum tensor is non-degenerate and also when it is degenerate. It
turns out that the non-degenerate case yields either {\it four}, {\it five},
{\it six}, {\it seven} or {\it ten} independent matter collineations in which
{\it four} are isometries and the rest are proper. There exists three
interesting cases where the energy-momentum tensor is degenerate but the group
of matter collineations is finite-dimensional. The matter collineations in
these cases are either {\it four}, {\it six} or {\it tenComment: 15 pages, LaTex, no figure
Kinematic Self-Similar Cylindrically Symmetric Solutions
This paper is devoted to find out cylindrically symmetric kinematic
self-similar perfect fluid and dust solutions. We study the cylindrically
symmetric solutions which admit kinematic self-similar vectors of second,
zeroth and infinite kinds, not only for the tilted fluid case but also for the
parallel and orthogonal cases. It is found that the parallel case gives
contradiction both in perfect fluid and dust cases. The orthogonal perfect
fluid case yields a vacuum solution while the orthogonal dust case gives
contradiction. It is worth mentioning that the tilted case provides solution
both for the perfect as well as dust cases.Comment: 22 pages, accepted for publication in Int. J. of Mod. Phys.
Plasma Wave Properties of the Schwarzschild Magnetosphere in a Veselago Medium
We re-formulate the 3+1 GRMHD equations for the Schwarzschild black hole in a
Veselago medium. Linear perturbation in rotating (non-magnetized and
magnetized) plasma is introduced and their Fourier analysis is considered. We
discuss wave properties with the help of wave vector, refractive index and
change in refractive index in the form of graphs. It is concluded that some
waves move away from the event horizon in this unusual medium. We conclude that
for the rotating non-magnetized plasma, our results confirm the presence of
Veselago medium while the rotating magnetized plasma does not provide any
evidence for this medium.Comment: 20 pages, 15 figures, accepted for publication in Astrophys. Space
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Evaluating the transition of e-Government: A review of local authorities in England
The goal of e-Government is seen as a panacea for governmental authorities. The emerging needs of citizens, their inclusion and engagement in policy development, political and participatory processes have meant new perspectives on e-Government are required. This paper seeks to identify and evaluate the preparedness of 10 UK-based local authorities to transition from basic e-Government to a more sophisticated and integrated e-Government. A categorical assessment of e-Government characteristics is made and these authorities are ranked accordingly. Our findings reveal the majority of local authorities sampled had reached a high percentage of informational and transactional e-Government but few had reached the interactional level and none had achieved assimilation. This suggests that local authorities seem to have focused on basic e-Government services. There is a need now to forge ahead to integration and assimilation of e-Government in order to address the critical objectives of citizen inclusion and engagement, and alignment of institutional processes to provide an infrastructure for the transition to e-governance and e-knowledge
Random sensory networks: a delay in analysis
A fundamental function performed by a sensory network is the retrieval of data gathered collectively by sensor nodes. The metrics that measure the efficiency of this data collection process are time and energy. In this paper, we study via simple discrete mathematical models, the statistics of the data collection time in sensory networks. Specifically, we analyze the average minimum delay in collecting randomly located/distributed sensors data for networks of various topologies when the number of nodes becomes large. Furthermore, we analyze the impact of various parameters such as size of packet, transmission range, and channel erasure probability on the optimal time performance. Our analysis applies to directional antenna systems as well as omnidirectional ones. This paper focuses on directional antenna systems and briefly presents results on omnidirectional antenna systems. Finally, a simple comparative analysis shows the respective advantages of the two systems
Kinematic Self-Similar Plane Symmetric Solutions
This paper is devoted to classify the most general plane symmetric spacetimes
according to kinematic self-similar perfect fluid and dust solutions. We
provide a classification of the kinematic self-similarity of the first, second,
zeroth and infinite kinds with different equations of state, where the
self-similar vector is not only tilted but also orthogonal and parallel to the
fluid flow. This scheme of classification yields twenty four plane symmetric
kinematic self-similar solutions. Some of these solutions turn out to be
vacuum. These solutions can be matched with the already classified plane
symmetric solutions under particular coordinate transformations. As a result,
these reduce to sixteen independent plane symmetric kinematic self-similar
solutions.Comment: 29 pages, accepted for publication in Classical Quantum Gravit
Isothermal Plasma Wave Properties of the Schwarzschild de-Sitter Black Hole in a Veselago Medium
In this paper, we study wave properties of isothermal plasma for the
Schwarzschild de-Sitter black hole in a Veselago medium. We use ADM 3+1
formalism to formulate general relativistic magnetohydrodynamical (GRMHD)
equations for the Schwarzschild de-Sitter spacetime in Rindler coordinates.
Further, Fourier analysis of the linearly perturbed GRMHD equations for the
rotating (non-magnetized and magnetized) background is taken whose determinant
leads to a dispersion relation. We investigate wave properties by using
graphical representation of the wave vector, the refractive index, change in
refractive index, phase and group velocities. Also, the modes of wave
dispersion are explored. The results indicate the existence of the Veselago
medium.Comment: 24 pages, 12 figures, accepted for publication in Astrophys. Space
Sci. arXiv admin note: text overlap with arXiv:1101.0884 and arxiv:1007.285
Cold Plasma Wave Analysis in Magneto-Rotational Fluids
This paper is devoted to investigate the cold plasma wave properties. The
analysis has been restricted to the neighborhood of the pair production region
of the Kerr magnetosphere. The Fourier analyzed general relativistic
magnetohydrodynamical equations are dealt under special circumstances and
dispersion relations are obtained. We find the -component of the complex
wave vector numerically. The corresponding components of the propagation
vector, attenuation vector, phase and group velocities are shown in graphs. The
direction and dispersion of waves are investigated.Comment: 22 pages, 18 figures, accepted for publication in Astrophys. Space
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