3,192 research outputs found
Perturbed Self-Similar Massless Scalar Field in Spherically Symmetric Spaceimes
In this paper, we investigate the linear perturbations of the spherically
symmetric spacetimes with kinematic self-similarity of the second kind. The
massless scalar field equations are solved which yield the background and an
exact solutions for the perturbed equations. We discuss the boundary conditions
of the resulting perturbed solutions. The possible perturbation modes turn out
to be stable as well as unstable. The analysis leads to the conclusion that
there does not exist any critical solution.Comment: 15 pages, accepted for publication Int. J. Mod. Phys.
Organizational energy: A behavioral analysis of human and organizational factors in manufacturing
This paper seeks to explore the behavior and embodied energy involved in the decision-making of information technology/information systems (IT/IS) investments using a case within a small- to medium-sized manufacturing firm. By analyzing decision making within a given case context, this paper describes the nature of the investment through the lens of behavioral economics, causality, input-output (IO) equilibrium, and the general notion of depletion of executive energy function. To explore the interplay between these elements, the authors structure the case context via a morphological field in order to construct a fuzzy cognitive map of decision-making relationships relating to the multidimensional and nonquantifiable problems of IT/IS investment evaluation. Noting the significance of inputs and outputs relating to the investment decision within the case, the authors assess these cognitive interrelationships through the lens of the Leontief IO energy equilibrium model. Subsequently, the authors suggest, through an embodied energy audit, that all such management decisions are susceptible to decision fatigue (so-called 'ego depletion'). The findings of this paper highlight pertinent cognitive and IO paths of the investment decision-making process that will allow others making similar types of investments to learn from and draw parallels from such processes
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
How much does transmit correlation affect the sum-rate scaling of MIMO Gaussian broadcast channels?
This paper considers the effect of spatial correlation between transmit antennas on the sum-rate capacity of the MIMO Gaussian broadcast channel (i.e., downlink of a cellular system). Specifically, for a system with a large number of users n, we analyze the scaling laws of the sum-rate for the dirty paper coding and for different types of beamforming transmission schemes. When the channel is i.i.d., it has been shown that for large n, the sum rate is equal to M log log n + M log P/M + o(1) where M is the number of transmit antennas, P is the average signal to noise ratio, and o(1) refers to terms that go to zero as n → ∞. When the channel exhibits some spatial correlation with a covariance matrix R (non-singular with tr(R) = M), we prove that the sum rate of dirty paper coding is M log log n + M log P/M + log det(R) + o(1). We further show that the sum-rate of various beamforming schemes achieves M log log n + M log P/M + M log c + o(1) where c ≤ 1 depends on the type of beamforming. We can in fact compute c for random beamforming proposed in and more generally, for random beamforming with preceding in which beams are pre-multiplied by a fixed matrix. Simulation results are presented at the end of the paper
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
Sc
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Integrating the IS with the enterprise: Key EAI research challenges
Enterprise Application Integration (EAI) technologies provide the means to integrate strategic business solutions within and across the component parts of organisational information system infrastructures. The continuing development of both digitally integrated business models, through various eCommerce and eBusiness initiatives, has meant that the importance of EAI within enterprise IS, has increased significantly. Noting that EAI incurs not only technological but stakeholder-level commitments, this paper outlines the product of a sustained investigation into key challenges within Enterprise IS and EAI, and provides a framework for future research and investigation into this emerging and evolving area
Gravitational Charged Perfect Fluid Collapse in Friedmann Universe Models
This paper is devoted to study the gravitational charged perfect fluid
collapse in the Friedmann universe models with cosmological constant. For this
purpose, we assume that the electromagnetic field is so weak that it does not
introduce any distortion into the geometry of the spacetime. The results
obtained from the junction conditions between the Friedmann and the
Reissner-Nordstrm de-Sitter spacetimes are used to solve the field
equations. Further, the singularity structure and mass effects of the
collapsing system on time difference between the formation of apparent horizons
and singularity have been studied. This analysis provides the validity of
Cosmic Censorship Hypothesis. It is found that the electric field affects the
area of apparent horizons and their time of formation.Comment: 17 pages, accepted for publication in Astrophys. Space Sc
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
Wave Properties of Plasma Surrounding the Event Horizon of a Non-Rotating Black Hole
We have studied the wave properties of the cold and isothermal plasma in the
vicinity of the Schwarzschild black hole event horizon. The Fourier analyzed
perturbed 3+1 GRMHD equations are taken on the basis of which the complex
dispersion relations are obtained for non-rotating, rotating non-magnetized and
rotating magnetized backgrounds. The propagation and attenuation vectors along
with the refractive index are obtained (shown in graphs) to study the
dispersive properties of the medium near the event horizon. The results show
that no information can be obtained from the Schwarzschild magnetosphere.
Further, the pressure ceases the existence of normal dispersion of waves.Comment: 31 pages, 21 figures, accepted for publication in Canadian J. Phy
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