173 research outputs found
Boundary Terms, Spinors and Kerr/CFT
Similarly as in AdS/CFT, the requirement that the action for spinors be
stationary for solutions to the Dirac equation with fixed boundary conditions
determines the form of the boundary term that needs to be added to the standard
Dirac action in Kerr/CFT. We determine this boundary term and make use of it to
calculate the two-point function for spinor fields in Kerr/CFT. This two-point
function agrees with the correlator of a two dimensional relativistic conformal
field theory.Comment: 15 page
Absorption cross section in warped AdS_3 black hole revisited
We investigate the absorption cross section for minimal-coupled scalars in
the warped AdS_3 black hole. According to our calculation, the cross section
reduces to the horizon area in the low energy limit as usually expected in
contrast to what was previously found. We also calculate the greybody factor
and find that the effective temperatures for the two chiral CFT's are
consistent with that derived from the quasinormal modes. Observing the
conjectured warped AdS/CFT correspondence, we suspect that a specific sector of
the CFT operators with the desired conformal dimension could be responsible for
the peculiar thermal behaviour of the warped AdS_3 black hole.Comment: 16+1 pages, typos corrected, references and footnotes adde
Greybody Factors and Charges in Kerr/CFT
We compute greybody factors for near extreme Kerr black holes in D=4 and D=5.
In D=4 we include four charges so that our solutions can be continuously
deformed to the BPS limit. In D=5 we include two independent angular momenta so
Left-Right symmetry is incorporated. We discuss the CFT interpretation of our
emission amplitudes, including the overall frequency dependence and the
dependence on all black hole parameters. We find that all additional parameters
can be incorporated Kerr/CFT, with central charge independent of U(1) charges.Comment: 27 pages. v2: typos fixed, references adde
Holographic Descriptions of Black Rings
In this paper, we investigate the holographic descriptions of two kinds of
black rings, the neutral doubly rotating black ring and the dipole charged
black ring. For generic nonextremal black rings, the information of holographic
CFT duals, including the central charges and left- and right-moving
temperatures, could be read from the thermodynamics at the outer and inner
horizons, as suggested in arXiv:1206.2015. To confirm these pictures, we study
the extreme black rings in the well-established formalism. We compute the
central charges of dual CFTs by doing asymptotic symmetry group analysis in the
stretched horizon formalism, and find exact agreements. Moreover, we study the
superradiant scattering of a scalar field off the near-extremal black rings and
obtain the scattering amplitudes, which are in good match with the CFT
predictions.Comment: 23 pages, no figures; some text overlap with arXiv:1206.201
Hidden and Generalized Conformal Symmetry of Kerr-Sen Spacetimes
It is recently conjectured that generic non-extremal Kerr black hole could be
holographically dual to a hidden conformal field theory in two dimensions.
Moreover, it is known that there are two CFT duals (pictures) to describe the
charged rotating black holes which correspond to angular momentum and
electric charge of the black hole. Furthermore these two pictures can be
incorporated by the CFT duals (general picture) that are generated by
modular group. The general conformal structure can be
revealed by looking at charged scalar wave equation in some appropriate values
of frequency and charge. In this regard, we consider the wave equation of a
charged massless scalar field in background of Kerr-Sen black hole and show in
the "near region", the wave equation can be reproduced by the Casimir operator
of a local hidden conformal
symmetry. We can find the exact agreement between macroscopic and microscopic
physical quantities like entropy and absorption cross section of scalars for
Kerr-Sen black hole. We then find an extension of vector fields that in turn
yields an extended local family of hidden conformal symmetries, parameterized by one
parameter. For some special values of the parameter, we find a copy of
hidden conformal algebra for the charged
Gibbons-Maeda-Garfinkle-Horowitz-Strominger black hole in the strong deflection
limit.Comment: 16 pages, new material and results added, extensive improvements in
interpretation of results, references adde
Holographic description of Kerr-Bolt-AdS-dS Spacetimes
We show that there exists a holographic 2D CFT description of a
Kerr-Bolt-AdS-dS spacetime. We first consider the wave equation of a massless
scalar field propagating in extremal Kerr-Bolt-AdS-dS spacetimes and find in
the "near region", the wave equation in extremal limit could be written in
terms of the quadratic Casimir. This suggests that there exist dual
CFT descriptions of these black holes. In the probe limit, we compute the
scattering amplitudes of the scalar off the extremal black holes and find
perfect agreement with the CFT prediction. Furthermore we study the holographic
description of the generic four dimensional non-extremal Kerr-Bolt-AdS-dS black
holes. We find that if focusing on the near-horizon region, for the massless
scalar scattering in the low-frequency limit, the radial equation could still
be rewritten as the quadratic Casimir, suggesting the existence of
dual 2D description. We read the temperatures of the dual CFT from the
conformal coordinates and obtain the central charges by studying the
near-horizon geometry of near-extremal black holes. We recover the macroscopic
entropy from the microscopic counting. We also show that for the superradiant
scattering, the retarded Green's functions and the corresponding absorption
cross sections are in perfect match with CFT prediction.Comment: 17 pages, typos corrected, references adde
Conformal mechanics inspired by extremal black holes in d=4
A canonical transformation which relates the model of a massive relativistic
particle moving near the horizon of an extremal black hole in four dimensions
and the conventional conformal mechanics is constructed in two different ways.
The first approach makes use of the action-angle variables in the angular
sector. The second scheme relies upon integrability of the system in the sense
of Liouville.Comment: V2: presentation improved, new material and references added; the
version to appear in JHE
Hidden Conformal Symmetry of Extremal Kerr-Bolt Spacetimes
We show that extremal Kerr-Bolt spacetimes have a hidden conformal symmetry.
In this regard, we consider the wave equation of a massless scalar field
propagating in extremal Kerr-Bolt spacetimes and find in the "near region", the
wave equation in extremal limit can be written in terms of the
quadratic Casimir. Moreover, we obtain the microscopic entropy of the extremal
Kerr-Bolt spacetimes also we calculate the correlation function of a
near-region scalar field and find perfect agreement with the dual 2D CFT.Comment: 13 page
Separability of Black Holes in String Theory
We analyze the origin of separability for rotating black holes in string
theory, considering both massless and massive geodesic equations as well as the
corresponding wave equations. We construct a conformal Killing-Stackel tensor
for a general class of black holes with four independent charges, then identify
two-charge configurations where enhancement to an exact Killing-Stackel tensor
is possible. We show that further enhancement to a conserved Killing-Yano
tensor is possible only for the special case of Kerr-Newman black holes. We
construct natural null congruences for all these black holes and use the
results to show that only the Kerr-Newman black holes are algebraically special
in the sense of Petrov. Modifying the asymptotic behavior by the subtraction
procedure that induces an exact SL(2)^2 also preserves only the conformal
Killing-Stackel tensor. Similarly, we find that a rotating Kaluza-Klein black
hole possesses a conformal Killing-Stackel tensor but has no further
enhancements.Comment: 27 page
Quasi-normal modes of warped black holes and warped AdS/CFT correspondence
We analytically calculate the quasi-normal modes of various perturbations of
spacelike stretched and null warped black holes. From AdS/CFT
correspondence, these quasi-normal modes are expected to appear as the poles in
momentum space of retarded Green functions of dual operators in CFT at finite
temperature. We find that this is indeed the case, after taking into account of
the subtle identification of quantum numbers. The subtlety comes from the fact
that only after appropriate coordinate transformation the asymptotic geometries
of warped black holes are the same as the ones of warped spacetimes. We
show that in general the quasi-normal modes are in good agreement with the
prediction of the warped AdS/CFT correspondence, up to a constant factor. As a
byproduct, we compute the conformal dimensions of boundary operators dual to
the perturbations. Our result gives strong support to the conjectured warped
AdS/CFT correspondence.Comment: 26 pages; typos corrected, references added; more clarifications,
match the version to appear in JHE
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