1,671 research outputs found
The stringy nature of the 2d type-0A black hole
We investigate the thermodynamics of the RR charged two-dimensional type-0A
black hole background at finite temperature, and compare with known 0A matrix
model results. It has been claimed that there is a disagreement for the free
energy between the spacetime and the dual matrix model. Here we find that this
discrepancy is sensitive to how the cutoff is implemented on the spacetime
side. In particular, the disagreement is resolved once we put the cutoff at a
fixed distance away from the horizon, as opposed to a fixed position in space.
Furthermore, the mass and the entropy of the black hole itself add up to an
analytic contribution to the free energy, which is precisely reproduced by the
0A matrix model. We also use results from the 0A matrix model to predict the
next to leading order contribution to the entropy of the black hole. Finally,
we note that the black hole is characterized by a Hagedorn growth in its
density of states below the Hagedorn temperature. This, together with other
results, suggests there is a phase transition at this temperature.Comment: 1+21 pages; v2: Substantial changes in the body of the paper, main
results the same. Clarified discussion on the thermodynamics, added section
on a phase transition, references added. v3: Typos corrected. v4: Final
version, to appear in JHE
(Anti-)Brane backreaction beyond perturbation theory
We improve on the understanding of the backreaction of anti-D6-branes in a
flux background that is mutually BPS with D6-branes. This setup is analogous to
the study of the backreaction of anti-D3-branes inserted in the KS throat, but
does not require us to smear the anti-branes or do a perturbative analysis
around the BPS background. We solve the full equations of motion near the
anti-D6-branes and show that only two boundary conditions are consistent with
the equations of motion. Upon invoking a topological argument we eliminate the
boundary condition with regular H flux since it cannot lead to a solution that
approaches the right kind of flux away from the anti-D6-brane. This leaves us
with a boundary condition which has singular, but integrable, H flux energy
density.Comment: 12 pages + appendices, 1 figure; v2: minor changes, version published
in JHE
Conformal Field Theory Interpretation of Black Hole Quasi-normal Modes
We obtain exact expressions for the quasi-normal modes of various spin for
the BTZ black hole. These modes determine the relaxation time of black hole
perturbations. Exact agreement is found between the quasi-normal frequencies
and the location of the poles of the retarded correlation function of the
corresponding perturbations in the dual conformal field theory. This then
provides a new quantitative test of the AdS/CFT correspondence.Comment: 4 pages, RevTeX, references adde
Scalar Synchrotron Radiation in the Schwarzschild-anti-de Sitter Geometry
We present a complete relativistic analysis for the scalar radiation emitted
by a particle in circular orbit around a Schwarzschild-anti-de Sitter black
hole. If the black hole is large, then the radiation is concentrated in narrow
angles- high multipolar distribution- i.e., the radiation is synchrotronic.
However, small black holes exhibit a totally different behavior: in the small
black hole regime, the radiation is concentrated in low multipoles. There is a
transition mass at , where is the AdS radius. This behavior is
new, it is not present in asymptotically flat spacetimes.Comment: 13 pages, 6 figures, published version. References adde
Building blocks of a black hole
What is the nature of the energy spectrum of a black hole ? The algebraic
approach to black hole quantization requires the horizon area eigenvalues to be
equally spaced. As stressed long ago by by Mukhanov, such eigenvalues must be
exponentially degenerate with respect to the area quantum number if one is to
understand black hole entropy as reflecting degeneracy of the observable
states. Here we construct the black hole states by means of a pair of "creation
operators" subject to a particular simple algebra, a slight generalization of
that for the harmonic oscillator. We then prove rigorously that the n-th area
eigenvalue is exactly 2 raised to the n-fold degenerate. Thus black hole
entropy qua logarithm of the number of states for fixed horizon area comes out
proportional to that area.Comment: PhysRevTeX, 14 page
Stability Constraints on Classical de Sitter Vacua
We present further no-go theorems for classical de Sitter vacua in Type II
string theory, i.e., de Sitter constructions that do not invoke
non-perturbative effects or explicit supersymmetry breaking localized sources.
By analyzing the stability of the 4D potential arising from compactification on
manfiolds with curvature, fluxes, and orientifold planes, we found that
additional ingredients, beyond the minimal ones presented so far, are necessary
to avoid the presence of unstable modes. We enumerate the minimal setups for
(meta)stable de Sitter vacua to arise in this context.Comment: 18 pages; v2: argument improved, references adde
Page charge of D-branes and its behavior in topologically nontrivial B-fields
The RR Page charges for the D(2p+1)-branes with B-field in type IIB
supergravity are constructed consistently from brane source currents. The
resulting Page charges are B-independent in the nontrivial and intricate way.
It is found that in topologically trivial B-field the Page charge is conserved,
but in the topologically nontrivial B-field it is no longer to be conserved,
instead there is a jump between two Page charges defined in each patch, and we
interpret this jump as Hanany-Witten effect.Comment: 25 pages, 4 figures, typos corrected and reference adde
Black hole collision with a scalar particle in three dimensional anti-de Sitter spacetime
We study the collision between a BTZ black hole and a test particle coupled
to a scalar field. We compute the power spectrum, the energy radiated and the
plunging waveforms for this process. We show that for late times the signal is
dominated by the quasinormal ringing. In terms of the AdS/CFT correspondence
the bulk gravity process maps into a thermal state, an expanding bubble and
gauge particles decaying into bosons of the associated operator. These latter
thermalize in a timescale predicted by the bulk theory.Comment: 5 pages, 3 figures;minor improvements; references adde
Spin chains and string theory
Recently, an impressive agreement was found between anomalous dimensions of
certain operators in N=4 SYM and rotating strings with two angular momenta in
the bulk of AdS5xS5. A one-loop field theory computation, which involves
solving a Heisenberg chain by means of the Bethe ansatz agrees with the large
angular momentum limit of a rotating string. We point out that the Heisenberg
chain can be equally well solved by using a sigma model approach. Moreover we
also show that a certain limit, akin to the BMN limit, leads exactly to the
same sigma model for a string rotating with large angular momentum. The
agreement is then at the level of the action. As an upshot we propose that the
rotating string should be identified with a coherent, semi-classical state
built out of the eigenstates of the spin chain. The agreement is then complete.
For example we show that the mean value of the spin gives, precisely, the
position of the string in the bulk. This suggests a more precise formulation of
the AdS/CFT correspondence in the large-N limit and also indicates a way to
obtain string theory duals of other gauge theories.Comment: 16 pages. LaTeX. v2: References and some comments added. v3:
References to more recent work adde
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