150 research outputs found
Applications of hidden symmetries to black hole physics
This work is a brief review of applications of hidden symmetries to black
hole physics. Symmetry is one of the most important concepts of the science. In
physics and mathematics the symmetry allows one to simplify a problem, and
often to make it solvable. According to the Noether theorem symmetries are
responsible for conservation laws. Besides evident (explicit) spacetime
symmetries, responsible for conservation of energy, momentum, and angular
momentum of a system, there also exist what is called hidden symmetries, which
are connected with higher order in momentum integrals of motion. A remarkable
fact is that black holes in four and higher dimensions always possess a set
(`tower') of explicit and hidden symmetries which make the equations of motion
of particles and light completely integrable. The paper gives a general review
of the recently obtained results. The main focus is on understanding why at all
black holes have something (symmetry) to hide.Comment: This is an extended version of the talks at NEB-14 conference
(June,Ioannina,Greece) and JGRG20 meeting (September, Kyoto, Japan
Predicting Potential Distribution of Orchis Galilaea in Lebanon Using GIS
Orchis galilaea is the only Lebanese orchid that is restricted geographically to Lebanon,
Palestine and Jordan. It is a terrestrial orchid that attracts its pollinator by sexual deception
while offering no reward. The full distribution of this orchid in Lebanon has not been
determined. This study is part of ongoing research into the population dynamics of the
orchid to form a management plan for its conservation. A Geographic Information System
(GIS) was used to identify the habitat characteristics of O. galilaea and map its
distribution in Lebanon by combining known locations with digital layers of
environmental variables, including topography, land cover, soil type, geology and
precipitation. Classes within each environmental parameter were defined and weighted
according to their frequency of occurrence at extant sites. A predictive GIS model was
developed by overlaying the five layers of the habitat characteristics. The predicted
distribution map of O. galilaea was then validated by confirming presence of the orchid
in the predicted locations and absence in the unsuitable areas through exploration field
trips. Eighty five locations were surveyed and seven previously unknown populations of
O. galilaea were discovered. These new O. galilaea locations were all correctly predicted
by the model as potential habitat. The accuracy of the model was confirmed as it was
significantly more likely to find the orchid in predicted suitable habitat compared with
unsuitable habitat. Combining ecological habitat characteristics using GIS proved to be a
useful tool to successfully predict the potential distribution of O. galilaea in Lebanon and
will assist in planning its conservation measures
Closed conformal Killing-Yano tensor and geodesic integrability
Assuming the existence of a single rank-2 closed conformal Killing-Yano
tensor with a certain symmetry we show that there exist mutually commuting
rank-2 Killing tensors and Killing vectors. We also discuss the condition of
separation of variables for the geodesic Hamilton-Jacobi equations.Comment: 17 pages, no figure, LaTe
Color Glass Condensate in Brane Models or Don't Ultra High Energy Cosmic Rays Probe Scale ?
In a previous work hep-ph/0203165 we have studied propagation of relativistic
particles in the bulk for some of most popular brane models. Constraints have
been put on the parameter space of these models by calculating the time delay
due to propagation in the bulk of particles created during the interaction of
Ultra High Energy Cosmic Rays with protons in the terrestrial atmosphere. The
question was however raised that probability of hard processes in which bulk
modes can be produced is small and consequently, the tiny flux of UHECRs can
not constrain brane models. Here we use Color Glass Condensate (CGC) model to
show that effects of extra dimensions are visible not only in hard processes
when the incoming particle hits a massive Kaluza-Klein mode but also through
the modification of soft/semi-hard parton distribution. At classical level, for
an observer in the CM frame of UHECR and atmospheric hadrons, color charge
sources are contracted to a thin sheet with a width inversely proportional to
the energy of the ultra energetic cosmic ray hadron and consequently they can
see an extra dimension with comparable size. Due to QCD interaction a short
life swarm of partons is produced in front of the sheet and its partons can
penetrate to the extra-dimension bulk. This reduces the effective density of
partons on the brane or in a classical view creates a delay in the arrival of
the most energetic particles if they are reflected back due to the warping of
the bulk. In CGC approximation the density of swarm at different distance from
the classical sheet can be related and therefore it is possible (at least
formally) to determine the relative fraction of partons in the bulk and on the
brane at different scales. Results of this work are also relevant to the test
of brane models in hadron colliders like LHC.Comment: 17 pages, 3 figures. Text is modified to highlight the relation
between the distribution gluons at high and low rapidity scales. v3:
published versio
Uniqueness of Rotating Charged Black Holes in Five-Dimensional Minimal Gauged Supergravity
We study a five-dimensional spacetime admitting, in the presence of torsion,
a non-degenerate conformal Killing-Yano 2-form which is closed with respect to
both the usual exterior differentiation and the exterior differentiation with
torsion. Furthermore, assuming that the torsion is closed and co-closed with
respect to the exterior differentiation with torsion, we prove that such a
spacetime is the only spacetime given by the Chong-Cvetic-Lu-Pope solution for
stationary, rotating charged black holes with two independent angular momenta
in five-dimensional minimal gauged supergravity.Comment: Dedicated to Nihat Berker on the occasion of his 60th birthday; 13
pages, REVTe
Kerr-NUT-de Sitter Curvature in All Dimensions
We explicitly calculate the Riemannian curvature of D-dimensional metrics
recently discussed by Chen, Lu and Pope. We find that they can be concisely
written by using a single function. The Einstein condition which corresponds to
the Kerr-NUT-de Sitter metric is clarified for all dimensions. It is shown that
the metrics are of type D.Comment: 10 page
Stationary strings and branes in the higher-dimensional Kerr-NUT-(A)dS spacetimes
We demonstrate complete integrability of the Nambu-Goto equations for a
stationary string in the general Kerr-NUT-(A)dS spacetime describing the
higher-dimensional rotating black hole. The stationary string in D dimensions
is generated by a 1-parameter family of Killing trajectories and the problem of
finding a string configuration reduces to a problem of finding a geodesic line
in an effective (D-1)-dimensional space. Resulting integrability of this
geodesic problem is connected with the existence of hidden symmetries which are
inherited from the black hole background. In a spacetime with p mutually
commuting Killing vectors it is possible to introduce a concept of a
-brane, that is a p-brane with the worldvolume generated by these fields
and a 1-dimensional curve. We discuss integrability of such -branes in the
Kerr-NUT-(A)dS spacetime.Comment: 8 pages, no figure
Closed conformal Killing-Yano tensor and uniqueness of generalized Kerr-NUT-de Sitter spacetime
The higher-dimensional Kerr-NUT-de Sitter spacetime describes the general
rotating asymptotically de Sitter black hole with NUT parameters. It is known
that such a spacetime possesses a rank-2 closed conformal Killing-Yano (CKY)
tensor as a ``hidden'' symmetry which provides the separation of variables for
the geodesic equations and Klein-Gordon equations. We present a classification
of higher-dimensional spacetimes admitting a rank-2 closed CKY tensor. This
provides a generalization of the Kerr-NUT-de Sitter spacetime. In particular,
we show that the Kerr-NUT-de Sitter spacetime is the only spacetime with a
non-degenerate CKY tensor.Comment: 24 pages, LaTeX; v2: references added, published versio
Multicentre evaluation of the Naída Ci Q70 sound processor: Feedback from cochlear implant users and professionals
The aim of this survey was to gather data from both implant recipients and professionals on the ease of use of the Naída CI Q70 (Naída CI) sound processor from Advanced Bionics and on the usefulness of the new functions and features available. A secondary objective was to investigate fitting practices with the new processor. A comprehensive user satisfaction survey was conducted in a total of 186 subjects from 24 centres. In parallel, 23 professional questionnaires were collected from 11 centres. Overall, there was high satisfaction with the Naída CI processor from adults, children, experienced and new CI users as well as from professionals. The Naída CI processor was shown as being easy to use by all ages of recipients and by professionals. The majority of experienced CI users rated the Naída CI processor as being similar or better than their previous processor in all areas surveyed. The Naída CI was recommended by the professionals for fitting in all populations. Features like UltraZoom, ZoomControl and DuoPhone would not be fitted to very young children in contrast to adults. Positive ratings were obtained for ease of use, comfort and usefulness of the new functions and features of the Naída CI sound processor. Seventy-seven percent of the experienced CI users rated the new processor as being better than their previous sound processor from a general point of view. The survey also showed that fitting practices were influenced by the age of the user
Hidden Symmetries and Black Holes
The paper contains a brief review of recent results on hidden symmetries in
higher dimensional black hole spacetimes. We show how the existence of a
principal CKY tensor (that is a closed conformal Killing-Yano 2-form) allows
one to generate a `tower' of Killing-Yano and Killing tensors responsible for
hidden symmetries. These symmetries imply complete integrability of geodesic
equations and the complete separation of variables in the Hamilton-Jacobi,
Klein-Gordon, Dirac and gravitational perturbation equations in the general
Kerr-NUT-(A)dS metrics. Equations of the parallel transport of frames along
geodesics in these spacetimes are also integrable.Comment: 13 pages, 3 figures. To appear in the proceedings of the NEB-13
conferenc
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