22,065 research outputs found
Mass of Rotating Black Holes in Gauged Supergravities
The masses of several recently-constructed rotating black holes in gauged
supergravities, including the general such solution in minimal gauged
supergravity in five dimensions, have until now been calculated only by
integrating the first law of thermodynamics. In some respects it is more
satisfactory to have a calculation of the mass that is based directly upon the
integration of a conserved quantity derived from a symmetry principal. In this
paper, we evaluate the masses for the newly-discovered rotating black holes
using the conformal definition of Ashtekar, Magnon and Das (AMD), and show that
the results agree with the earlier thermodynamic calculations. We also consider
the Abbott-Deser (AD) approach, and show that this yields an identical answer
for the mass of the general rotating black hole in five-dimensional minimal
gauged supergravity. In other cases we encounter discrepancies when applying
the AD procedure. We attribute these to ambiguities or pathologies of the
chosen decomposition into background AdS metric plus deviations when scalar
fields are present. The AMD approach, involving no decomposition into
background plus deviation, is not subject to such complications. Finally, we
also calculate the Euclidean action for the five-dimensional solution in
minimal gauged supergravity, showing that it is consistent with the quantum
statistical relation.Comment: Typos corrected and references update
The image ray transform for structural feature detection
The use of analogies to physical phenomena is an exciting paradigm in computer vision that allows unorthodox approaches to feature extraction, creating new techniques with unique properties. A technique known as the "image ray transform" has been developed based upon an analogy to the propagation of light as rays. The transform analogises an image to a set of glass blocks with refractive index linked to pixel properties and then casts a large number of rays through the image. The course of these rays is accumulated into an output image. The technique can successfully extract tubular and circular features and we show successful circle detection, ear biometrics and retinal vessel extraction. The transform has also been extended through the use of multiple rays arranged as a beam to increase robustness to noise, and we show quantitative results for fully automatic ear recognition, achieving 95.2% rank one recognition across 63 subjects
Transonic Elastic Model for Wiggly Goto-Nambu String
The hitherto controversial proposition that a ``wiggly" Goto-Nambu cosmic
string can be effectively represented by an elastic string model of exactly
transonic type (with energy density inversely proportional to its tension
) is shown to have a firm mathematical basis.Comment: 8 pages, plain TeX, no figure
A Killing tensor for higher dimensional Kerr-AdS black holes with NUT charge
In this paper, we study the recently discovered family of higher dimensional
Kerr-AdS black holes with an extra NUT-like parameter. We show that the inverse
metric is additively separable after multiplication by a simple function. This
allows us to separate the Hamilton-Jacobi equation, showing that geodesic
motion is integrable on this background. The separation of the Hamilton-Jacobi
equation is intimately linked to the existence of an irreducible Killing
tensor, which provides an extra constant of motion. We also demonstrate that
the Klein-Gordon equation for this background is separable.Comment: LaTeX, 14 pages. v2: Typo corrected and equation added. v3: Reference
added, introduction expanded, published versio
Extremal Black Hole/CFT Correspondence in (Gauged) Supergravities
We extend the investigation of the recently proposed Kerr/CFT correspondence
to large classes of rotating black hole solutions in gauged and ungauged
supergravities. The correspondence, proposed originally for four-dimensional
Kerr black holes, asserts that the quantum states in the near-horizon region of
an extremal rotating black hole are holographically dual to a two-dimensional
chiral theory whose Virasoro algebra arises as an asymptotic symmetry of the
near-horizon geometry. In fact in dimension D there are [(D-1)/2] commuting
Virasoro algebras. We consider a general canonical class of near-horizon
geometries in arbitrary dimension D, and show that in any such metric, the
[(D-1)/2] central charges each imply, via the Cardy formula, a microscopic
entropy that agrees with the Bekenstein-Hawking entropy of the associated
extremal black hole. In the remainder of the paper we show for most of the
known rotating black hole solutions of gauged supergravity, and for the
ungauged supergravity solutions with four charges in D=4 and three charges in
D=5, that their extremal near-horizon geometries indeed lie within the
canonical form. This establishes that in all these examples, the microscopic
entropies of the dual CFTs agree with the Bekenstein-Hawking entropies of the
extremal rotating black holes.Comment: 32 pages, references added and minor typos fixe
Holographic Screening Length in a Hot Plasma of Two Sphere
We study the screening length of a quark-antiquark pair moving in a hot
plasma living in two sphere manifold using AdS/CFT correspondence where
the background metric is four dimensional Schwarzschild-AdS black hole. The
geodesic solution of the string ends at the boundary is given by a stationary
motion in the equatorial plane as such the separation length of
quark-antiquark pair is parallel to the angular velocity . The
screening length and the bound energy are computed numerically using
Mathematica. We find that the plots are bounded from below by some functions
related to the momentum transfer of the drag force configuration. We
compare the result by computing the screening length in the quark-antiquark
reference frame where the gravity dual are "Boost-AdS" and Kerr-AdS black
holes. Finding relations of the parameters of both black holes, we argue that
the relation between mass parameters of the Schwarzschild-AdS black
hole and of the Kerr-AdS black hole in high temperature is given by
, where is the angular momentum
parameter.Comment: Major revision: title changed, adding authors, 13 pages, 8 figures,
etc. Accepted for publication in European Physical Journal
Geometric scaling in high-energy QCD at nonzero momentum transfer
We show how one can obtain geometric scaling properties from the
Balitsky-Kovchegov (BK) equation. We start by explaining how, this property
arises for the b-independent BK equation. We show that it is possible to extend
this model to the full BK equation including momentum transfer. The saturation
scale behaves like max(q,Q_T) where q is the momentum transfer and Q_T a
typical scale of the target.Comment: 4 pages, 2 figures. Talk given by G. Soyez at the "Rencontres de
Moriond", 12-19 March 2005, La Thuile, Ital
Phase Structure of Kerr-AdS Black Hole
We study the critical phenomena of Kerr-AdS black hole. Phase structures are
observed at different temperatures, , and with various
features. We discuss the thermal stability considering the isothermal
compressibility and how phase transitions related to each other. The asymptotic
value of the angular momentum also has an implication on separating stable and
unstable part. Near critical temperature , the order parameter is
determined to calculate the critical exponents. All the critical exponents
(,,,)=(0,1/2,1,3) are identical to that of mean
field systems. We plot the phase diagram near this critical point, and discuss
the scaling symmetry of the free energy.Comment: 21 pages, 6 figures, contents revise
Rotating Black Holes in Higher Dimensions with a Cosmological Constant
We present the metric for a rotating black hole with a cosmological constant
and with arbitrary angular momenta in all higher dimensions. The metric is
given in both Kerr-Schild and Boyer-Lindquist form. In the Euclidean-signature
case, we also obtain smooth compact Einstein spaces on associated S^{D-2}
bundles over S^2, infinitely many for each odd D\ge 5. Applications to string
theory and M-theory are indicated.Comment: 8 pages, Latex. Short version, with more compact notation, of
hep-th/0404008. To appear in Phys. Rev. Let
Late acceleration and crossing in induced gravity
We study the cosmological evolution on a brane with induced gravity within a
bulk with arbitrary matter content. We consider a Friedmann-Robertson-Walker
brane, invariantly characterized by a six-dimensional group of isometries. We
derive the effective Friedmann and Raychaudhuri equations. We show that the
Hubble expansion rate on the brane depends on the covariantly defined
integrated mass in the bulk, which determines the energy density of the
generalized dark radiation. The Friedmann equation has two branches,
distinguished by the two possible values of the parameter \ex=\pm 1. The
branch with \ex=1 is characterized by an effective cosmological constant and
accelerated expansion for low energy densities. Another remarkable feature is
that the contribution from the generalized dark radiation appears with a
negative sign. As a result, the presence of the bulk corresponds to an
effective negative energy density on the brane, without violation of the weak
energy condition. The transition from a period of domination of the matter
energy density by non-relativistic brane matter to domination by the
generalized dark radiation corresponds to a crossing of the phantom divide
.Comment: 7 pages, no figures, RevTex 4.0; (v2) new references are added, minor
corrections and expanded discussion; (v3) additional comments at the end of
section III, minor corrections and several new references are added, to match
published version in Phys. Rev.
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