8,789 research outputs found
Strong gravitational lensing across dilaton anti-de Sitter black hole
In this work we investigate gravitational lensing effect in strong field
region around a dilaton black holes in an anti de Sitter (ADS) space. We also
analyse the dependence of the radius of the photon sphere and deflection angle
on dilaton coupling and cosmological constant in this black hole space time.
Finally the values of minimum impact parameter, the separation between the
first and the other images as well as the ratio between the flux of the first
image and the flux coming from all the other images are determined to
characterize some possible distinct signatures of such black holes.Comment: 8 pages and 3 figures. Accepted in Physical Review
Generating dynamical black hole solutions
We prove a theorem that characterizes a large family of non-static solutions
to Einstein equations, representing, in general, spherically symmetric Type II
fluid. It is shown that the best known dynamical black hole solutions to
Einstein equations are particular cases from this family. Thus we extend a
recent work of Salgado \cite{ms} to non-static case. The spherically symmetric
static black hole solutions, for Type I fluid, are also retrieved.Comment: 8 Pages, RevTe
Solute Concentration Effects on Microstructure and the Compressive Strength of Ice-Templated Sintered Lithium Titanate
This work investigated the role of sucrose and cationic dispersant (1‐hexadecyl)trimethylammonium bromide concentration on ice‐templated sintered lithium titanate microstructure and compressive strength, to enable a comprehensive understanding of composition selection and elucidate processing–microstructure–mechanical property relationships. Sucrose and dispersant concentrations were varied to change total solute concentration in suspensions and viscosity. Dispersant was more effective in reducing viscosity than sucrose; however, their combination had an even greater impact on reducing viscosity. Based on viscosity measurements, a total of 12 suspension compositions were developed, and materials were fabricated at two different freezing front velocity (FFV) regimes. Solute concentration greatly influenced ice‐templated microstructure and microstructure development improved with solute concentration. Depending on solute concentration, type of solute, viscosity, and FFV, a wide variety of microstructures were observed ranging from lamellar to dendritic morphologies. Solute concentration effect was rationalized based on solid–liquid planar interface instability. For suspensions with comparable viscosity, solute concentration can be varied to tune microstructure, whereas for suspensions with comparable solute concentration, viscosity variation can tune microstructure. Compressive strength of sintered materials generally increased with total solute concentration, sucrose concentration, viscosity, and FFV. Due to the wide variety of microstructure, strength also varied over a wide range, 23–128 MPa
Supersymmetric Many-particle Quantum Systems with Inverse-square Interactions
The development in the study of supersymmetric many-particle quantum systems
with inverse-square interactions is reviewed. The main emphasis is on quantum
systems with dynamical OSp(2|2) supersymmetry. Several results related to
exactly solved supersymmetric rational Calogero model, including shape
invariance, equivalence to a system of free superoscillators and non-uniqueness
in the construction of the Hamiltonian, are presented in some detail. This
review also includes a formulation of pseudo-hermitian supersymmetric quantum
systems with a special emphasis on rational Calogero model. There are quite a
few number of many-particle quantum systems with inverse-square interactions
which are not exactly solved for a complete set of states in spite of the
construction of infinitely many exact eigen functions and eigenvalues. The
Calogero-Marchioro model with dynamical SU(1,1|2) supersymmetry and a quantum
system related to short-range Dyson model belong to this class and certain
aspects of these models are reviewed. Several other related and important
developments are briefly summarized.Comment: LateX, 65 pages, Added Acknowledgment, Discussions and References,
Version to appear in Jouranl of Physics A: Mathematical and Theoretical
(Commissioned Topical Review Article
Radiating black holes in Einstein-Yang-Mills theory and cosmic censorship
Exact nonstatic spherically symmetric black-hole solution of the higher
dimensional Einstein-Yang-Mills equations for a null dust with Yang-Mills gauge
charge are obtained by employing Wu-Yang \textit{ansatz}, namely, HD-EYM Vaidya
solution. It is interesting to note that gravitational contribution of YM gauge
charge for this ansatz is indeed opposite (attractive rather than repulsive)
that of Maxwell charge. It turns out that the gravitational collapse of null
dust with YM gauge charge admit strong curvature shell focusing naked
singularities violating cosmic censorship. However, there is significant
shrinkage of the initial data space for a naked singularity of the HD-Vaidya
collapse due to presence of YM gauge charge. The effect of YM gauge charge on
structure and location of the apparent and event horizons is also discussed.Comment: 9 RevTeX pages, 1 figur
The toxic continuum from incivility to violence: What can HRD do
Abstract The frequency, intensity, and duration of uncivil behavior should be a concern to leaders in any organization. All too often seemingly isolated, subtle uncivil incidents (e.g., instigating a joke) can lead to patterns of uncivil behavior (e.g., bullying) and even physical violence. Each is a form of aggressive behavior. Inasmuch as uncivil behavior is linked to poorer individual-(e.g., job performance) and organizational-level (e.g., costs) outcomes, human resource development (HRD) is increasingly being called to implement useful strategies for dealing effectively with this vital workplace issue. The article traces the more subtle forms of uncivil behavior that tend to be ambiguous in intent to more intentional forms of uncivil behavior, that is, bullying and physical violence. The article suggests that HRD can make a strong, positive contribution to reducing the likelihood of uncivil behaviors, which in turn can play a meaningful role in increasing the success of the organization. Finally, a summary of the eight articles are presented that comprise this issue
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