136 research outputs found
Planar quark scattering at strong coupling and universality
We discuss scattering of fundamental matter in the planar and strong coupling
limit via the AdS/CFT correspondence, generalizing the recently proposed
calculation for adjoint matter due to Alday and Maldacena [arXiv:0705.0303].
Color decomposition of quark amplitudes is a key property allowing to repeat
the procedure in the case of fundamental matter and to derive the relation of
these strong coupling amplitudes to minimal area problems. We present the
results for two different D3-D7 systems, one is only conformal in the planar
limit and the other is exactly conformal. Our results suggest a universal
behavior of scattering amplitudes at strong coupling and planar limit (both for
gluons and quarks).Comment: 13 pages, 4 figures, JHEP format. v2: added references and minor
corrections. v3: following arXiv:0710.0393 we change our claim about a
minimal surface solution without spike singularities. We make the appropriate
corrections where necessar
A Matrix Model for AdS2
A matrix quantum mechanics with potential and an SL(2,R)
conformal symmetry is conjectured to be dual to two-dimensional type 0A string
theory on AdS with units of RR flux.Comment: 12 page
M-Theory Giant Gravitons with C field
We find giant graviton configurations of an M5-brane probe in the D=11
supergravity background generated by a stack of non-threshold (M2,M5) bound
states. The M5-brane probe shares three directions with the background and
wraps a two-sphere transverse to the bound states. For a particular value of
the worldvolume gauge field of the PST formalism, there exist solutions of the
equations of motion for which the M5-brane probe behaves as a wave propagating
in the (M2,M5) background. We have checked that the probe breaks the
supersymmetry of the background exactly as a massless particle moving along the
trajectory of its center of mass.Comment: 11 pages, LaTeX; v2: references adde
Non-commutative holography and scattering amplitudes in a large magnetic background
We study planar gluon scattering amplitudes and Wilson loops in
non-commutative gauge theory. Our main results are:
1. We find the map between observables in non-commutative gauge theory and
their holographic dual. In that map, the region near the boundary of the
gravitational dual describes the physics in terms of T-dual variables.
2. We show that in the presence of a large magnetic background and a UV
regulator, a planar gluon scattering amplitude reduces to a complex polygon
Wilson loop expectation value, dressed by a tractable polarization dependent
factor.Comment: 26 pages. v2: corrected section 4, reference adde
Squashed Giants: Bound States of Giant Gravitons
We consider giant gravitons in the maximally supersymmetric type IIB
plane-wave, in the presence of a constant NSNS B-field background. We show that
in response to the background B-field the giant graviton would take the shape
of a deformed three-sphere, the size and shape of which depend on the B-field,
and that the giant becomes classically unstable once the B-field is larger than
a critical value B_{cr}. In particular, for the B-field which is
(anti-)self-dual under the SO(4) isometry of the original giant S^3, the closed
string metric is that of a round S^3, while the open string metric is a
squashed three-sphere. The squashed giant can be interpreted as a bound state
of a spherical three-brane and circular D-strings. We work out the spectrum of
geometric fluctuations of the squashed giant and study its stability. We also
comment on the gauge theory which lives on the brane (which is generically a
noncommutative theory) and a possible dual gauge theory description of the
deformed giant.Comment: Latex file, 32 pages, 6 .eps figures; v3: typos correcte
The Conformal Limit of the 0A Matrix Model and String Theory on AdS(2)
We analyze the conformal limit of the matrix model describing flux
backgrounds of two dimensional type 0A string theory. This limit is believed to
be dual to an AdS(2) background of type 0A string theory. We show that the
spectrum of this limit is identical to that of a free fermion on AdS(2),
suggesting that there are no closed string excitations in this background.Comment: 17 pages, 1 figur
A Holographic View on Matrix Model of Black Hole
We investigate a deformed matrix model proposed by Kazakov et.al. in relation
to Witten's two-dimensional black hole. The existing conjectures assert the
equivalence of the two by mapping each to a deformed c=1 theory called the
sine-Liouville theory. We point out that the matrix theory in question may be
naturally interpreted as a gauged quantum mechanics deformed by insertion of an
exponentiated Wilson loop operator, which gives us more direct and holographic
map between the two sides. The matrix model in the usual scaling limit must
correspond to the bosonic SL(2,R)/U(1) theory in genus expansion but exact in
\alpha'. We successfully test this by computing the Wilson loop expectation
value and comparing it against the bulk computation. For the latter, we employ
the \alpha'-exact geometry proposed by Dijkgraaf, Verlinde, and Verlinde, which
was further advocated by Tseytlin. We close with comments on open problems.Comment: LaTeX, 19 page
Noncritical String Correlators, Finite-N Matrix Models and the Vortex Condensate
We carry out a systematic study of correlation functions of momentum modes in
the Euclidean c=1 string, as a function of the radius and to all orders in
perturbation theory. We obtain simple explicit expressions for several classes
of correlators in terms of special functions. The Normal Matrix Model is found
to be a powerful calculational tool that computes c=1 string correlators even
at finite N. This enables us to obtain a simple combinatoric formula for the
2n-point function of unit momentum modes, which after T-duality determines the
vortex condensate. We comment on possible applications of our results to
T-duality at c=1 and to the 2d black hole/vortex condensate problem.Comment: 38 pages, LaTe
Thermodynamics of R-charged Black Holes in AdS(5) From Effective Strings
It is well known that the thermodynamics of certain near-extremal black holes
in asymptotically flat space can be lifted to an effective string description
created from the intersection of D-branes. In this paper we present evidence
that the semiclassical thermodynamics of near-extremal R-charged black holes in
AdS(5)xS(5) is described in a similar manner by effective strings created from
the intersection of giant gravitons on the S(5). We also present a free fermion
description of the supersymmetric limit of the one-charge black hole, and we
give a crude catalog of the microstates of the two and three-charge black holes
in terms of operators in the dual conformal field theory.Comment: v2: references and typos corrected, 24 pages, latex2
Reverse Monte Carlo modeling of amorphous silicon
An implementation of the Reverse Monte Carlo algorithm is presented for the
study of amorphous tetrahedral semiconductors. By taking into account a number
of constraints that describe the tetrahedral bonding geometry along with the
radial distribution function, we construct a model of amorphous silicon using
the reverse monte carlo technique. Starting from a completely random
configuration, we generate a model of amorphous silicon containing 500 atoms
closely reproducing the experimental static structure factor and bond angle
distribution and in improved agreement with electronic properties. Comparison
is made to existing Reverse Monte Carlo models, and the importance of suitable
constraints beside experimental data is stressed.Comment: 6 pages, 4 PostScript figure
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