1,946 research outputs found
How many black holes fit on the head of a pin?
The Bekenstein-Hawking entropy of certain black holes can be computed
microscopically in string theory by mapping the elusive problem of counting
microstates of a strongly gravitating black hole to the tractable problem of
counting microstates of a weakly coupled D-brane system, which has no event
horizon, and indeed comfortably fits on the head of a pin. We show here that,
contrary to widely held beliefs, the entropy of spherically symmetric black
holes can easily be dwarfed by that of stationary multi-black-hole
``molecules'' of the same total charge and energy. Thus, the corresponding
pin-sized D-brane systems do not even approximately count the microstates of a
single black hole, but rather those of a zoo of entropically dominant
multicentered configurations.Comment: 4 pages, fourth prize in the Gravity Research Foundation Essay
competition 200
Universal features of the holographic duality: conformal anomaly and brane gravity trapping from 5d AdS Black Hole
We calculate the holographic conformal anomaly and brane Newton potential
when bulk is 5d AdS BH. It is shown that such anomaly is the same as in the
case of pure AdS or (asymptotically) dS bulk spaces, i.e. it is (bulk) metric
independent one. While Newton potential on the static brane in AdS BH is
different from the one in pure AdS space, the gravity trapping still occurs for
two branes system. This indicates to metric independence of gravity
localization.Comment: LaTeX file, 14 page
Real decoupling ghost quantization of the CGHS model for two dimensional black holes
A complete RST quantization of a CGHS model plus Strominger term is carried
out. In so doing a conformal invariant theory with is
found, that is, without ghosts contribution. The physical consequences of the
model are analysed and positive definite Hawking radiation is found.Comment: 14 pages, latex, no figures, marginal errors correcte
Universal Low-Energy Dynamics for Rotating Black Holes
Fundamental string theory has been used to show that low energy excitations
of certain black holes are described by a two dimensional conformal field
theory. This picture has been found to be extremely robust. In this paper it is
argued that many essential features of the low energy effective theory can be
inferred directly from a semiclassical analysis of the general Kerr-Newman
solution of supersymmetric four-dimensional Einstein-Maxwell gravity, without
using string theory. We consider the absorption and emission of scalars with
orbital angular momentum, which provide a sensitive probe of the black hole. We
find that the semiclassical emission rates -including superradiant emission and
greybody factors - for such scalars agree in striking detail with those
computed in the effective conformal field theory, in both four and five
dimensions. Also the value of the quantum mass gap to the lowest-lying
excitation of a charge- black hole, in Planck units, can be
derived without knowledge of fundamental string theory.Comment: 24 pages, no figures. Typos corrected, some comments adde
Microscopic Entropy of N=2 Extremal Black Holes
String theory is used to compute the microscopic entropy for several examples
of black holes in compactifications with supersymmetry. Agreement with
the Bekenstein-Hawking entropy and the moduli-independent area formula is
found in all cases.Comment: 9 pages, no figures, uses harvma
State/Operator Correspondence in Higher-Spin dS/CFT
A recently conjectured microscopic realization of the dS/CFT
correspondence relating Vasiliev's higher-spin gravity on dS to a Euclidean
CFT is used to illuminate some previously inaccessible aspects of
the dS/CFT dictionary. In particular it is argued that states of the boundary
CFT on are holographically dual to bulk states on geodesically
complete, spacelike slices which terminate on an at future
infinity. The dictionary is described in detail for the case of free scalar
excitations. The ground states of the free or critical model are dual
to dS-invariant plane-wave type vacua, while the bulk Euclidean vacuum is dual
to a certain mixed state in the CFT. CFT states created by operator
insertions are found to be dual to (anti) quasinormal modes in the bulk. A norm
is defined on the bulk Hilbert space and shown for the scalar case to be
equivalent to both the Zamolodchikov and pseudounitary C-norm of the
CFT.Comment: 24 page
Macroscopic and Microscopic Entropy of Near-Extremal Spinning Black Holes
A seven parameter family of five-dimensional black hole solutions depending
on mass, two angular momenta, three charges and the asymptotic value of a
scalar field is constructed. The entropy is computed as a function of these
parameters both from the Bekenstein-Hawking formula and from the degeneracies
of the corresponding D-brane states in string theory. The expressions agree at
and to leading order away from extremality.Comment: 7 pages, harvma
Bubbling solutions, entropy enhancement and the fuzzball proposal
In this short note we explain the main idea of the work done in
arXiv:0804.4487[hep-th] and arXiv:0812.2942[hep-th]. We present a family of
black hole microstates, the bubbling solutions. We then explain how supertubes
placed in such backgrounds have their entropy enhanced by the presence of the
background dipole charges. This indicates this could account for a large amount
in the entropy of the three charge black hole.Comment: 2 pages, contribution to the Cargese 2008 proceedings: Theory and
Particle Physics: the LHC perspective and beyon
Classical central extension for asymptotic symmetries at null infinity in three spacetime dimensions
The symmetry algebra of asymptotically flat spacetimes at null infinity in
three dimensions is the semi-direct sum of the infinitesimal diffeomorphisms on
the circle with an abelian ideal of supertranslations. The associated charge
algebra is shown to admit a non trivial classical central extension of Virasoro
type closely related to that of the anti-de Sitter case.Comment: 4 sign mistakes due to a change of conventions are corrected in
section 2, none of the conclusions are affected, takes precedence over
published version, including corrigendu
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