194 research outputs found
D-brane Construction of the 5D NHEK Dual
Extremal but non-supersymmetric charged black holes with SU(2)_L spin in IIB
string theory compactified to five dimensions on K^3 x S^1 are considered.
These have a near-horizon or NHEK region with an enhanced SL(2,R)_L conformal
symmetry. It is shown that the NHEK geometry has a second, inequivalent,
asymptotically flat extension in which the radius of the S^1 becomes infinite
but the radius of the angular circles of SU(2)_L orbits approach a constant.
The asymptotic charges associated to the second solution identify it as a 5D
D1-D5-Taub-NUT black string with certain nonzero worldvolume charge densities,
temperatures and chemical potentials. The dual of the NHEK geometry is then
identified as an IR limit of this wrapped brane configuration.Comment: 11 page
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
Particle Dynamics in Weakly Charged Extreme Kerr Throat
We study dynamics of a test charged particle moving in a weakly charged
extreme Kerr throat. Dynamical equations of the particle motion are solved in
quadratures. We show explicitly that the Killing tensor of the Kerr spacetime
becomes reducible in the extreme Kerr throat geometry. Special types of motion
of particles and light are discussed.Comment: The paper is prepared for the fest volume devoted to 75th Birthday of
Mario Castagnin
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
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
Incompressible Fluids of the de Sitter Horizon and Beyond
There are (at least) two surfaces of particular interest in eternal de Sitter
space. One is the timelike hypersurface constituting the lab wall of a static
patch observer and the other is the future boundary of global de Sitter space.
We study both linear and non-linear deformations of four-dimensional de Sitter
space which obey the Einstein equation. Our deformations leave the induced
conformal metric and trace of the extrinsic curvature unchanged for a fixed
hypersurface. This hypersurface is either timelike within the static patch or
spacelike in the future diamond. We require the deformations to be regular at
the future horizon of the static patch observer. For linearized perturbations
in the future diamond, this corresponds to imposing incoming flux solely from
the future horizon of a single static patch observer. When the slices are
arbitrarily close to the cosmological horizon, the finite deformations are
characterized by solutions to the incompressible Navier-Stokes equation for
both spacelike and timelike hypersurfaces. We then study, at the level of
linearized gravity, the change in the discrete dispersion relation as we push
the timelike hypersurface toward the worldline of the static patch. Finally, we
study the spectrum of linearized solutions as the spacelike slices are pushed
to future infinity and relate our calculations to analogous ones in the context
of massless topological black holes in AdS.Comment: 27 pages, 8 figure
The holographic fluid dual to vacuum Einstein gravity
We present an algorithm for systematically reconstructing a solution of the
(d+2)-dimensional vacuum Einstein equations from a (d+1)-dimensional fluid,
extending the non-relativistic hydrodynamic expansion of Bredberg et al in
arXiv:1101.2451 to arbitrary order. The fluid satisfies equations of motion
which are the incompressible Navier-Stokes equations, corrected by specific
higher derivative terms. The uniqueness and regularity of this solution is
established to all orders and explicit results are given for the bulk metric
and the stress tensor of the dual fluid through fifth order in the hydrodynamic
expansion. We establish the validity of a relativistic hydrodynamic description
for the dual fluid, which has the unusual property of having a vanishing
equilibrium energy density. The gravitational results are used to identify
transport coefficients of the dual fluid, which also obeys an interesting and
exact constraint on its stress tensor. We propose novel Lagrangian models which
realise key properties of the holographic fluid.Comment: 31 pages; v2: references added and minor improvements, published
versio
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
Causality and the AdS Dirichlet problem
The (planar) AdS Dirichlet problem has previously been shown to exhibit
superluminal hydrodynamic sound modes. This problem is defined by bulk
gravitational dynamics with Dirichlet boundary conditions imposed on a rigid
timelike cut-off surface. We undertake a careful examination of this set-up and
argue that, in most cases, the propagation of information between points on the
Dirichlet hypersurface is nevertheless causal with respect to the induced light
cones. In particular, the high-frequency dynamics is causal in this sense.
There are however two exceptions and both involve boundary gravitons whose
propagation is not constrained by the Einstein equations. These occur in i)
AdS, where the boundary gravitons generally do not respect the induced
light cones on the boundary, and ii) Rindler space, where they are related to
the infinite speed of sound in incompressible fluids. We discuss implications
for the fluid/gravity correspondence with rigid Dirichlet boundaries and for
the black hole membrane paradigm.Comment: 29 pages, 5 figures. v2: added refs. v3: minor clarification
From Petrov-Einstein to Navier-Stokes in Spatially Curved Spacetime
We generalize the framework in arXiv:1104.5502 to the case that an embedding
may have a nonvanishing intrinsic curvature. Directly employing the Brown-York
stress tensor as the fundamental variables, we study the effect of finite
perturbations of the extrinsic curvature while keeping the intrinsic metric
fixed. We show that imposing a Petrov type I condition on the hypersurface
geometry may reduce to the incompressible Navier-Stokes equation for a fluid
moving in spatially curved spacetime in the near-horizon limit.Comment: 17 pages, references added, generalizing the metric form in part 3,
version published in JHE
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