564 research outputs found

### Holography of Charged Dilaton Black Holes

We study charged dilaton black branes in $AdS_4$. Our system involves a
dilaton $\phi$ coupled to a Maxwell field $F_{\mu\nu}$ with dilaton-dependent
gauge coupling, ${1\over g^2} = f^2(\phi)$. First, we find the solutions for
extremal and near extremal branes through a combination of analytical and
numerical techniques. The near horizon geometries in the simplest cases, where
$f(\phi) = e^{\alpha\phi}$, are Lifshitz-like, with a dynamical exponent $z$
determined by $\alpha$. The black hole thermodynamics varies in an interesting
way with $\alpha$, but in all cases the entropy is vanishing and the specific
heat is positive for the near extremal solutions. We then compute conductivity
in these backgrounds. We find that somewhat surprisingly, the AC conductivity
vanishes like $\omega^2$ at T=0 independent of $\alpha$. We also explore the
charged black brane physics of several other classes of gauge-coupling
functions $f(\phi)$. In addition to possible applications in AdS/CMT, the
extremal black branes are of interest from the point of view of the attractor
mechanism. The near horizon geometries for these branes are universal,
independent of the asymptotic values of the moduli, and describe generic
classes of endpoints for attractor flows which are different from $AdS_2\times
R^2$.Comment: 33 pages, 3 figures, LaTex; v2, references added; v3, more refs
added; v4, refs added, minor correction

### Finite-Temperature Fractional D2-Branes and the Deconfinement Transition in 2+1 Dimensions

The supergravity dual to N regular and M fractional D2-branes on the cone
over \mathbb{CP}^3 has a naked singularity in the infrared. One can resolve
this singularity and obtain a regular fractional D2-brane solution dual to a
confining 2+1 dimensional N = 1 supersymmetric field theory. The confining
vacuum of this theory is described by the solution of Cvetic, Gibbons, Lu and
Pope. In this paper, we explore the alternative possibility for resolving the
singularity - the creation of a regular horizon. The black-hole solution we
find corresponds to the deconfined phase of this dual gauge theory in three
dimensions. This solution is derived in perturbation theory in the number of
fractional branes. We argue that there is a first-order deconfinement
transition. Connections to Chern--Simons matter theories, the ABJM proposal and
fractional M2-branes are presented.Comment: v3: analytic solutions are expose

### Holographic metals at finite temperature

A holographic dual description of a 2+1 dimensional system of strongly
interacting fermions at low temperature and finite charge density is given in
terms of an electron cloud suspended over the horizon of a charged black hole
in asymptotically AdS spacetime. The electron star of Hartnoll and Tavanfar is
recovered in the limit of zero temperature, while at higher temperatures the
fraction of charge carried by the electron cloud is reduced and at a critical
temperature there is a second order phase transition to a configuration with
only a charged black hole. The geometric structure implies that finite
temperature transport coefficients, including the AC electrical conductivity,
only receive contributions from bulk fermions within a finite band in the
radial direction.Comment: LaTex 16 pages, 12 figures, v2: Added reference. Error in free energy
corrected. Phase transition to AdS-RN black brane is third order rather than
second order as was claimed previousl

### AdS Phase Transitions at finite \kappa

We investigate the effect of adding a Chern-Simons term coupled to an axion
field to SU(2) Einstein-Yang-Mills in a fixed $AdS_4$/Schwarzschild background.
We show that, when the axion has no potential, there is a phase transition
between a Reissner-Nordstrom black-hole and one with a non-abelian condensate
as per the vanishing Chern-Simons case. Furthermore, by giving the axion field
a mass, one observes a phase transition between a Reissner-Nordstrom black-hole
with axion hair to a "superconducting" phase which also has a non-trivial axion
profile. We are able to perform a preliminary analysis for this interesting
case and observe that we can shift the critical temperature at which the phase
transition occurs and observe interesting features of the order parameter
scaling form.Comment: Version Published in JHE

### Thermodynamics of string black hole with hyperscaling violation

In this paper, we start with black brane and construct specific space-time
which violates hyperscaling. In order to obtain the string solution we apply
Null-Melvin-Twist and $KK$-reduction. By using the difference action method we
study thermodynamics of system to obtain Hawking-Page phase transition. In
order to have hyperscaling violation we need to consider $\theta=\frac{d}{2}.$
In that case the free energy $F$ is always negative and our solution is thermal
radiation without a black hole. Therefore we find that there is not any
Hawking-Page transition. Also, we discuss the stability of system and all
thermodynamical quantities.Comment: 12 pages. Accepted for publication in EPJ

### Charged Dilatonic AdS Black Branes in Arbitrary Dimensions

We study electromagnetically charged dilatonic black brane solutions in
arbitrary dimensions with flat transverse spaces, that are asymptotically AdS.
This class of solutions includes spacetimes which possess a bulk region where
the metric is approximately invariant under Lifshitz scalings. Given fixed
asymptotic boundary conditions, we analyze how the behavior of the bulk up to
the horizon varies with the charges and derive the extremality conditions for
these spacetimes.Comment: References update

### The influence of D-branes' backreaction upon gravitational interactions between open strings

We argue that gravitational interactions between open strings ending on
D3-branes are largely shaped by the D3-branes' backreaction. To this end we
consider classical open strings coupled to general relativity in Poincare AdS5
backgrounds. We compute the linear gravitational backreaction of a static
string extending up to the Poincare horizon, and deduce the potential energy
between two such strings. If spacetime is non-compact, we find that the
gravitational potential energy between parallel open strings is independent of
the strings' inertial masses and goes like 1/r at large distance r. If the
space transverse to the D3-branes is suitably compactified, a collective mode
of the graviton propagates usual four-dimensional gravity. In that case the
backreaction of the D3-branes induces a correction to the Newtonian potential
energy that violates the equivalence principle. The observed enhancement of the
gravitational attraction is specific to string theory; there is no similar
effect for point-particles.Comment: 28 pages, 7 figures. Typos corrected, minor addition

### Assessing a candidate IIA dual to metastable supersymmetry-breaking

We analyze the space of linearized non-supersymmetric deformations around a
IIA solution found by Cvetic, Gibbons, Lu and Pope (CGLP) in hep-th/0101096. We
impose boundary conditions aimed at singling out among those perturbations
those describing the backreaction of anti-D2 branes on the CGLP background. The
corresponding supergravity solution is a would-be dual to a metastable
supersymmetry-breaking state. However, it turns out that this candidate bulk
solution is inevitably riddled with IR divergences of its flux densities and
action, whose physical meaning and implications for models of string cosmology
call for further investigation.Comment: 33 pages. v2: reference added, clarifications in the introductio

### Anisotropic Drag Force from 4D Kerr-AdS Black Holes

Using AdS/CFT we investigate the effect of angular-momentum-induced
anisotropy on the instantaneous drag force of a heavy quark. The dual
description is that of a string moving in the background of a Kerr-AdS black
holes. The system exhibits the expected focussing of jets towards the impact
parameter plane. We put forward that we can use the connection between this
focussing behavior and the angular momentum induced pressure gradient to
extrapolate the pressure gradient correction to the drag force that can be used
for transverse elliptic flow in realistic RHIC. The result is recognizable as a
relativistic pressure gradient force.Comment: 22 pages and 4 figure

### Holographic Anyons in the ABJM Theory

We consider the holographic anyons in the ABJM theory from three different
aspects of AdS/CFT correspondence. First, we identify the holographic anyons by
using the field equations of supergravity, including the Chern-Simons terms of
the probe branes. We find that the composite of Dp-branes wrapped over CP3 with
the worldvolume magnetic fields can be the anyons. Next, we discuss the
possible candidates of the dual anyonic operators on the CFT side, and find the
agreement of their anyonic phases with the supergravity analysis. Finally, we
try to construct the brane profile for the holographic anyons by solving the
equations of motion and Killing spinor equations for the embedding profile of
the wrapped branes. As a by product, we find a BPS spiky brane for the dual
baryons in the ABJM theory.Comment: 1+33 pages, 3 figures; v2 discussion for D4-D6 case added, references
added; v3 comments adde

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