192 research outputs found
Wilson Loops in the Higgs Phase of Large N Field Theories on the Conifold
We study the quark-antiquark interaction in the large N limit of the
superconformal field theory on D-3branes at a Calabi-Yau conical singularity.
We compute the Wilson loop in the AdS_5xT^{11} supergravity background for the
SU(2N)x SU(2N) theory. We also calculate the Wilson loop for the Higgs phase
where the gauge group is broken to SU(N)x SU(N)x SU_D(N). This corresponds to a
two center configuration with some of the branes at the singularity and the
rest of them at a smooth point. The calculation exhibits the expected Coulomb
dependence for the interaction. The angular distribution of the BPS states is
different than the one for a spherical horizon.Comment: Latex2e file. 19 pages. Final versio
Boundary Causality vs Hyperbolicity for Spherical Black Holes in Gauss-Bonnet
We explore the constraints boundary causality places on the allowable
Gauss-Bonnet gravitational couplings in asymptotically AdS spaces, specifically
considering spherical black hole solutions. We additionally consider the
hyperbolicity properties of these solutions, positing that
hyperbolicity-violating solutions are sick solutions whose causality properties
provide no information about the theory they reside in. For both signs of the
Gauss-Bonnet coupling, spherical black holes violate boundary causality at
smaller absolute values of the coupling than planar black holes do. For
negative coupling, as we tune the Gauss-Bonnet coupling away from zero, both
spherical and planar black holes violate hyperbolicity before they violate
boundary causality. For positive coupling, the only hyperbolicity-respecting
spherical black holes which violate boundary causality do not do so appreciably
far from the planar bound. Consequently, eliminating hyperbolicity-violating
solutions means the bound on Gauss-Bonnet couplings from the boundary causality
of spherical black holes is no tighter than that from planar black holes.Comment: 17 pages, 6 figure
Jet Quenching and Holographic Thermalization with a Chemical Potential
We investigate jet quenching of virtual gluons and thermalization of a
strongly-coupled plasma with a non-zero chemical potential via the
gauge/gravity duality. By tracking a charged shell falling in an asymptotic
AdS background for and , which is characterized by the
AdS-Reissner-Nordstr\"om-Vaidya (AdS-RN-Vaidya) geometry, we extract a
thermalization time of the medium with a non-zero chemical potential. In
addition, we study the falling string as the holographic dual of a virtual
gluon in the AdS-RN-Vaidya spacetime. The stopping distance of the massless
particle representing the tip of the falling string in such a spacetime could
reveal the jet quenching of an energetic light probe traversing the medium in
the presence of a chemical potential. We find that the stopping distance
decreases when the chemical potential is increased in both AdS-RN and
AdS-RN-Vaidya spacetimes, which correspond to the thermalized and thermalizing
media respectively. Moreover, we find that the soft gluon with an energy
comparable to the thermalization temperature and chemical potential in the
medium travels further in the non-equilibrium plasma. The thermalization time
obtained here by tracking a falling charged shell does not exhibit,
generically, the same qualitative features as the one obtained studying
non-local observables. This indicates that --holographically-- the definition
of thermalization time is observer dependent and there is no unambiguos
definition.Comment: 25 pages, 15 figures, minor modification, references adde
Strong Subadditivity, Null Energy Condition and Charged Black Holes
Using the Hubeny-Rangamani-Takayanagi (HRT) conjectured formula for
entanglement entropy in the context of the AdS/CFT correspondence with
time-dependent backgrounds, we investigate the relation between the bulk null
energy condition (NEC) of the stress-energy tensor with the strong
sub-additivity (SSA) property of entanglement entropy in the boundary theory.
In a background that interpolates between an AdS to an
AdS-Reissner-Nordstrom-type geometry, we find that generically there always
exists a critical surface beyond which the violation of NEC would naively
occur. However, the extremal area surfaces that determine the entanglement
entropy for the boundary theory, can penetrate into this forbidden region only
for certain choices for the mass and the charge functions in the background.
This penetration is then perceived as the violation of SSA in the boundary
theory. We also find that this happens only when the critical surface lies
above the apparent horizon, but not otherwise. We conjecture that SSA, which is
thus non-trivially related to NEC, also characterizes the entire time-evolution
process along which the dual field theory may thermalize.Comment: 27 pages, v3 matches the published versio
Weak Field Collapse in AdS: Introducing a Charge Density
We study the effect of a non-vanishing chemical potential on the
thermalization time of a strongly coupled large gauge theory in
-dimensions, using a specific bottom-up gravity model in asymptotically
AdS space. We first construct a perturbative solution to the gravity-equations,
which dynamically interpolates between two AdS black hole backgrounds with
different temperatures and chemical potentials, in a perturbative expansion of
a bulk neutral scalar field. In the dual field theory, this corresponds to a
quench dynamics by a marginal operator, where the corresponding coupling serves
as the small parameter in which the perturbation is carried out. The evolution
of non-local observables, such as the entanglement entropy, suggests that
thermalization time decreases with increasing chemical potential. We also
comment on the validity of our perturbative analysis.Comment: 1+48 pages, multiple figures, published in JHE
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