2,802 research outputs found
Low temperature properties of holographic condensates
In the current work we study various models of holographic superconductors at
low temperature. Generically the zero temperature limit of those models are
solitonic solution with a zero sized horizon. Here we generalized simple
version of those zero temperature solutions to small but non-zero temperature
T. We confine ourselves to cases where near horizon geometry is AdS^4. At a
non-zero temperature a small horizon would form deep inside this AdS^4 which
does not disturb the UV physics. The resulting geometry may be matched with the
zero temperature solution at an intermediate length scale. We understand this
matching from separation of scales by setting up a perturbative expansion in
gauge potential. We have a better analytic control in abelian case and
quantities may be expressed in terms of hypergeometric function. From this we
calculate low temperature behavior of various quatities like entropy, charge
density and specific heat etc. We also calculate various energy gaps associated
with p-wave holographic superconductor to understand the underlying pairing
mechanism. The result deviates significantly from the corresponding weak
coupling BCS counterpart.Comment: 17 Page
Universality of the diffusion wake in the gauge-string duality
As a particle moves through a fluid, it may generate a laminar wake behind
it. In the gauge-string duality, we show that such a diffusion wake is created
by a heavy quark moving through a thermal plasma and that it has a universal
strength when compared to the total drag force exerted on the quark by the
plasma. The universality extends over all asymptotically anti-de Sitter
supergravity constructions with arbitrary scalar matter. We discuss how these
results relate to the linearized hydrodynamic approximation and how they bear
on our understanding of di-hadron correlators in heavy ion collisions.Comment: 36 pages, 4 figure
Massive-Scalar Absorption by Extremal p-branes
We study the absorption probability of minimally-coupled massive scalars by
extremal p-branes. In particular, we find that the massive scalar wave equation
under the self-dual string background has the same form as the massless scalar
wave equation under the dyonic string background. Thus it can be cast into the
form of a modified Mathieu equation and solved exactly. Another example that we
can solve exactly is that of the D=4 two-charge black hole with equal charges,
for which we obtain the closed-form absorption probability. We also obtain the
leading-order absorption probabilities for D3-, M2- and M5-branes.Comment: Latex, 11 pages, reference adde
Zero Temperature Limit of Holographic Superconductors
We consider holographic superconductors whose bulk description consists of
gravity minimally coupled to a Maxwell field and charged scalar field with
general potential. We give an analytic argument that there is no "hard gap":
the real part of the conductivity at low frequency remains nonzero (although
typically exponentially small) even at zero temperature. We also numerically
construct the gravitational dual of the ground state of some holographic
superconductors. Depending on the charge and dimension of the condensate, the
infrared theory can have emergent conformal or just Poincare symmetry. In all
cases studied, the area of the horizon of the dual black hole goes to zero in
the extremal limit, consistent with a nondegenerate ground state.Comment: 27 pages, 8 figure
Non-supersymmetric deformations of the dual of a confining gauge theory
We introduce a computational technique for studying non-supersymmetric
deformations of domain wall solutions of interest in AdS/CFT. We focus on the
Klebanov-Strassler solution, which is dual to a confining gauge theory. From an
analysis of asymptotics we find that there are three deformations that leave
the ten-dimensional supergravity solution regular and preserve the global
bosonic symmetries of the supersymmetric solution. Also, we show that there are
no regular near-extremal deformations preserving the global symmetries, as one
might expect from the existence of a gap in the gauge theory.Comment: 18 pages, latex, published as JHEP 0305 (2003) 03
The gauge-string duality and heavy ion collisions
I review at a non-technical level the use of the gauge-string duality to
study aspects of heavy ion collisions, with special emphasis on the trailing
string calculation of heavy quark energy loss. I include some brief
speculations on how variants of the trailing string construction could provide
a toy model of black hole formation and evaporation. This essay is an invited
contribution to "Forty Years of String Theory" and is aimed at philosophers and
historians of science as well as physicists.Comment: 21 page
p-wave Holographic Superconductors and five-dimensional gauged Supergravity
We explore five-dimensional and
SO(6) gauged supergravities as frameworks for condensed matter applications.
These theories contain charged (dilatonic) black holes and 2-forms which have
non-trivial quantum numbers with respect to U(1) subgroups of SO(6). A question
of interest is whether they also contain black holes with two-form hair with
the required asymptotic to give rise to holographic superconductivity. We first
consider the case, which contains a complex two-form potential
which has U(1) charge . We find that a slight
generalization, where the two-form potential has an arbitrary charge , leads
to a five-dimensional model that exhibits second-order superconducting
transitions of p-wave type where the role of order parameter is played by
, provided . We identify the operator that condenses
in the dual CFT, which is closely related to Super Yang-Mills
theory with chemical potentials. Similar phase transitions between R-charged
black holes and black holes with 2-form hair are found in a generalized version
of the gauged supergravity Lagrangian where the two-forms have
charge .Comment: 35 pages, 14 figure
Exact Absorption Probability in the Extremal Six-Dimensional Dyonic String Background
We show that the minimally coupled massless scalar wave equation in the
background of an six-dimensional extremal dyonic string (or D1-D5 brane
intersection) is exactly solvable, in terms of Mathieu functions. Using this
fact, we calculate absorption probabilities for these scalar waves, and present
the explicit results for the first few low energy corrections to the
leading-order expressions. For a specific tuning of the dyonic charges one can
reach a domain where the low energy absorption probability goes to zero with
inverse powers of the logarithm of the energy. This is a dividing domain
between the regime where the low energy absorption probability approaches zero
with positive powers of energy and the regime where the probability is an
oscillatory function of the logarithm of the energy. By the conjectured AdS/CFT
correspondence, these results shed novel light on the strongly coupled
two-dimensional field theory away from its infrared conformally invariant fixed
point (the strongly coupled ``non-critical'' string).Comment: Latex (3 times), 23 page
Asymptotic Symmetry and the General Black Hole Solution in Ads_3 Gravity
We describe the Brown-Henneaux asymptotic symmetry of the general black holes
in the Chern-Simons gauge theory of the gauge group . We make it clear that the vector-like subgroup plays an essential role in describing the asymptotic symmetry
consistently. We find a quite general black hole solution in the
gravity theory. The solution is specified by an infinite number of conserved
quantities which constitute a family of mapping from to the gauge group.
The BTZ black hole is one of the simplest case.Comment: 19 pages, no figur
Greybody factor for D3-branes in B field
We calculate the effect of noncommutative spacetime on the greybody factor on
the supergravity side. For this purpose we introduce a system of D3-branes with
a constant NS -field along their world volume directions ().
Considering the propagation of minimally coupled scalar with non-zero momentum
along(), we derive an exact form of the greybody factor in field.
It turns out that . This means that the
presence of -field (the noncommutativity) suppresses the potential barrier
surrounding the black hole. As a result, it comes out the increase of greybody
factor.Comment: some discussions and references are added, 10 pages, no figure,
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