224 research outputs found
Generalized hidden symmetries and the Kerr-Sen black hole
We elaborate on basic properties of generalized Killing-Yano tensors which
naturally extend Killing-Yano symmetry in the presence of skew-symmetric
torsion. In particular, we discuss their relationship to Killing tensors and
the separability of various field equations. We further demonstrate that the
Kerr-Sen black hole spacetime of heterotic string theory, as well as its
generalization to all dimensions, possesses a generalized closed conformal
Killing-Yano 2-form with respect to a torsion identified with the 3-form
occuring naturally in the theory. Such a 2-form is responsible for complete
integrability of geodesic motion as well as for separability of the scalar and
Dirac equations in these spacetimes.Comment: 33 pages, no figure
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
A Deformation of Sasakian Structure in the Presence of Torsion and Supergravity Solutions
We discuss a deformation of Sasakian structure in the presence of totally
skew-symmetric torsion by introducing odd dimensional manifolds whose metric
cones are K\"ahler with torsion. It is shown that such a geometry inherits
similar properties to those of Sasakian geometry. As an example of them, we
present an explicit expression of local metrics and see how Sasakian structure
is deformed by the presence of torsion. We also demonstrate that our example of
the metrics admits the existence of hidden symmetries described by non-trivial
odd-rank generalized closed conformal Killing-Yano tensors. Furthermore, using
these metrics as an {\it ansatz}, we construct exact solutions in five
dimensional minimal (un-)gauged supergravity and eleven dimensional
supergravity. Finally, we discuss the global structures of the solutions and
obtain regular metrics on compact manifolds in five dimensions, which give
natural generalizations of Sasaki--Einstein manifolds and
. We also discuss regular metrics on non-compact manifolds in eleven
dimensions.Comment: 38 pages, 1 table, v2: version to appear in Class. Quant. Gra
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
Symmetries of the Dirac operator with skew-symmetric torsion
In this paper, we consider the symmetries of the Dirac operator derived from
a connection with skew-symmetric torsion. We find that the generalized
conformal Killing-Yano tensors give rise to symmetry operators of the massless
Dirac equation, provided an explicitly given anomaly vanishes. We show that
this gives rise to symmetries of the Dirac operator in the case of strong
Kahler with torsion (KT) and strong hyper-Kahler with torsion (HKT) manifolds
Some Spacetimes with Higher Rank Killing-Stackel Tensors
By applying the lightlike Eisenhart lift to several known examples of
low-dimensional integrable systems admitting integrals of motion of
higher-order in momenta, we obtain four- and higher-dimensional Lorentzian
spacetimes with irreducible higher-rank Killing tensors. Such metrics, we
believe, are first examples of spacetimes admitting higher-rank Killing
tensors. Included in our examples is a four-dimensional supersymmetric pp-wave
spacetime, whose geodesic flow is superintegrable. The Killing tensors satisfy
a non-trivial Poisson-Schouten-Nijenhuis algebra. We discuss the extension to
the quantum regime
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
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