30 research outputs found
Charged Lifshitz Black Holes
We investigate modifications of the Lifshitz black hole solutions due to the
presence of Maxwell charge in higher dimensions for arbitrary and any
topology. We find that the behaviour of large black holes is insensitive to the
topology of the solutions, whereas for small black holes significant
differences emerge. We generalize a relation previously obtained for neutral
Lifshitz black branes, and study more generally the thermodynamic relationship
between energy, entropy, and chemical potential. We also consider the effect of
Maxwell charge on the effective potential between objects in the dual theory.Comment: Latex, 28 pages, 14 figures, some references adde
A Holographic Quantum Hall Ferromagnet
A detailed numerical study of a recent proposal for exotic states of the
D3-probe D5 brane system with charge density and an external magnetic field is
presented. The state has a large number of coincident D5 branes blowing up to a
D7 brane in the presence of the worldvolume electric and magnetic fields which
are necessary to construct the holographic state. Numerical solutions have
shown that these states can compete with the the previously known chiral
symmetry breaking and maximally symmetric phases of the D3-D5 system. Moreover,
at integer filling fractions, they are incompressible with integer quantized
Hall conductivities. In the dual superconformal defect field theory, these
solutions correspond to states which break the chiral and global flavor
symmetries spontaneously. The region of the temperature-density plane where the
D7 brane has lower energy than the other known D5 brane solutions is
identified. A hypothesis for the structure of states with filling fraction and
Hall conductivity greater than one is made and tested by numerical computation.
A parallel with the quantum Hall ferromagnetism or magnetic catalysis
phenomenon which is observed in graphene is drawn. As well as demonstrating
that the phenomenon can exist in a strongly coupled system, this work makes a
number of predictions of symmetry breaking patterns and phase transitions for
such systems.Comment: 38 pages, 7 figures, references adde
Thermodynamic Instability of Black Holes of Third Order Lovelock Gravity
In this paper, we compute the mass and the temperature of the uncharged black
holes of third order Lovelock gravity and compute the entropy through the use
of first law of thermodynamics. We perform a stability analysis by studying the
curves of temperature versus the mass parameter, and find that there exists an
intermediate thermodynamically unstable phase for black holes with hyperbolic
horizon. The existence of this unstable phase for the uncharged topological
black holes of third order Lovelock gravity does not occur in the lower order
Lovelock gravity. We also perform a stability analysis for a spherical,
7-dimensional black hole of Lovelock gravity and find that while these kinds of
black holes for small values of Lovelock coefficients have an intermediate
unstable phase, they are stable for large values of Lovelock coefficients. We
also find that there exists an intermediate unstable phase for these black
holes in higher dimensions. This stability analysis shows that the
thermodynamic stability of black holes with curved horizons is not a robust
feature of all the generalized theories of gravity.Comment: 16 pages, 8 figure
Gauss-Bonnet Black Holes and Heavy Fermion Metals
We consider charged black holes in Einstein-Gauss-Bonnet Gravity with
Lifshitz boundary conditions. We find that this class of models can reproduce
the anomalous specific heat of condensed matter systems exhibiting
non-Fermi-liquid behaviour at low temperatures. We find that the temperature
dependence of the Sommerfeld ratio is sensitive to the choice of Gauss-Bonnet
coupling parameter for a given value of the Lifshitz scaling parameter. We
propose that this class of models is dual to a class of models of
non-Fermi-liquid systems proposed by Castro-Neto et.al.Comment: 17 pages, 6 figures, pdfLatex; small corrections to figure 10 in this
versio
Chameleon Gravity, Electrostatics, and Kinematics in the Outer Galaxy
Light scalar fields are expected to arise in theories of high energy physics
(such as string theory), and find phenomenological motivations in dark energy,
dark matter, or neutrino physics. However, the coupling of light scalar fields
to ordinary (or dark) matter is strongly constrained from laboratory, solar
system, and astrophysical tests of fifth force. One way to evade these
constraints in dense environments is through the chameleon mechanism, where the
field's mass steeply increases with ambient density. Consequently, the
chameleonic force is only sourced by a thin shell near the surface of dense
objects, which significantly reduces its magnitude.
In this paper, we argue that thin-shell conditions are equivalent to
"conducting" boundary conditions in electrostatics. As an application, we use
the analogue of the method of images to calculate the back-reaction (or
self-force) of an object around a spherical gravitational source. Using this
method, we can explicitly compute the violation of equivalence principle in the
outskirts of galactic haloes (assuming an NFW dark matter profile):
Intermediate mass satellites can be slower than their larger/smaller
counterparts by as much as 10% close to a thin shell.Comment: 17 pages, 3 figure
Corner contributions to holographic entanglement entropy
The entanglement entropy of three-dimensional conformal field theories
contains a universal contribution coming from corners in the entangling
surface. We study these contributions in a holographic framework and, in
particular, we consider the effects of higher curvature interactions in the
bulk gravity theory. We find that for all of our holographic models, the corner
contribution is only modified by an overall factor but the functional
dependence on the opening angle is not modified by the new gravitational
interactions. We also compare the dependence of the corner term on the new
gravitational couplings to that for a number of other physical quantities, and
we show that the ratio of the corner contribution over the central charge
appearing in the two-point function of the stress tensor is a universal
function for all of the holographic theories studied here. Comparing this
holographic result to the analogous functions for free CFT's, we find fairly
good agreement across the full range of the opening angle. However, there is a
precise match in the limit where the entangling surface becomes smooth, i.e.,
the angle approaches , and we conjecture the corresponding ratio is a
universal constant for all three-dimensional conformal field theories. In this
paper, we expand on the holographic calculations in our previous letter
arXiv:1505.04804, where this conjecture was first introduced.Comment: 62 pages, 6 figures, 1 table; v2: minor modifications to match
published version, typos fixe