2,259 research outputs found
Electric-Magnetic Duality and Topological Insulators
We work out the action of the SL(2,Z) electric-magnetic duality group for an
insulator with a non-trivial permittivity, permeability and theta-angle. This
theory has recently been proposed to be the correct low-energy effective action
for topological insulators. As applications, we give manifestly SL(2,Z)
covariant expressions for the Faraday rotation at orthogonal incidence at the
interface of two such materials, as well as for the induced magnetic and
electric charges, slightly clarifying the meaning of expressions previously
derived in the literature. We also use electric-magnetic duality to find a
gravitational dual for a strongly coupled version of this theory using the
AdS/CFT correspondence.Comment: 4 pages; version accepted by PR
Notes on Properties of Holographic Matter
Probe branes with finite worldvolume electric flux in the background created
by a stack of Dp branes describe holographically strongly interacting
fundamental matter at finite density. We identify two quantities whose leading
low temperature behavior is independent of the dimensionality of the probe
branes: specific heat and DC conductivity. This behavior can be inferred from
the dynamics of the fundamental strings which provide a good description of the
probe branes in the regime of low temperatures and finite densities. We also
comment on the speed of sound on the branes and the temperature dependence of
DC conductivity at vanishing charge density.Comment: 18 pages, 2 figures; v2: corrected error in Section 6, conclusions
unchanged; v3: improved figures and added clarifying comment
Critical Exponents from AdS/CFT with Flavor
We use the AdS/CFT correspondence to study the thermodynamics of massive N=2
supersymmetric hypermultiplet flavor fields coupled to N=4 supersymmetric
SU(Nc) Yang-Mills theory, formulated on curved four-manifolds, in the limits of
large Nc and large 't Hooft coupling. The gravitational duals are probe
D-branes in global thermal AdS. These D-branes may undergo a topology-changing
transition in the bulk. The D-brane embeddings near the point of the topology
change exhibit a scaling symmetry. The associated scaling exponents can be
either real- or complex-valued. Which regime applies depends on the
dimensionality of a collapsing submanifold in the critical embedding. When the
scaling exponents are complex-valued, a first-order transition associated with
the flavor fields appears in the dual field theory. Real scaling exponents are
expected to be associated with a continuous transition in the dual field
theory. For one example with real exponents, the D7-brane, we study the
transition in detail. We find two field theory observables that diverge at the
critical point, and we compute the associated critical exponents. We also
present analytic and numerical evidence that the transition expresses itself in
the meson spectrum as a non-analyticity at the critical point. We argue that
the transition we study is a true phase transition only when the 't Hooft
coupling is strictly infinite.Comment: 31 pages, 21 eps files in 12 figures; v2 added one reference and one
footnote, version published in JHE
Bedside differentiation of vestibular neuritis from central "vestibular pseudoneuritis".
Acute unilateral peripheral and central vestibular lesions
can cause similar signs and symptoms, but they require
different diagnostics and management. We therefore
correlated clinical signs to differentiate vestibular neuritis
(40 patients) from central ‘‘vestibular pseudoneuritis’’ (43
patients) in the acute situation with the final diagnosis
assessed by neuroimaging. Skew deviation was the only
specific but non-sensitive (40%) sign for pseudoneuritis.
None of the other isolated signs (head thrust test,
saccadic pursuit, gaze evoked nystagmus, subjective
visual vertical) were reliable; however, multivariate
logistic regression increased their sensitivity and specificity
to 92%
Particle-vortex duality from 3D bosonization
We provide a simple derivation of particle-vortex duality in d=2+1
dimensions. Our starting point is a relativistic form of flux attachment,
designed to transmute the statistics of particles. From this seed, we derive a
web of new dualities. These include particle-vortex duality for bosons as well
as the recently discovered counterpart for fermions.US Department of Energy (Grant ID: DE-SC0011637), Science and Technology Facilities Council, European Research Council under the European Union’s Seventh Framework Programme (FP7/2007-2013) (GrantID: STG 279943, “Strongly Coupled Systems”), Stanford Institute for Theoretical Physics, University of WashingtonThis is the final version of the article. It first appeared from the American Physical Society via http://dx.doi.org/10.1103/PhysRevX.6.03104
The Stress-Energy Tensor of Flavor Fields from AdS/CFT
We use the AdS/CFT correspondence to study the transport properties of
massive N=2 hypermultiplet fields in an N=4 SU(Nc) super-Yang-Mills theory
plasma in the large Nc, large 't Hooft coupling limit, and in the presence of a
baryon number chemical potential and external electric and magnetic fields. In
particular, we compute the flavor fields' contribution to the stress-energy
tensor. We find infrared divergences in the stress-energy tensor, arising from
the flavor fields' constant rate of energy and momentum loss. We regulate these
divergences and extract the energy and momentum loss rates from the divergent
terms. We also check our result in various limits in which the divergences are
absent. The supergravity dual is a system of D7-branes, with a particular
configuration of worldvolume fields, probing an AdS-Schwarzschild background.
The supergravity calculation amounts to computing the stress-energy tensor of
the D7-branes.Comment: 32 pages; v2, added one footnote in section 2.2, added one reference,
version published in JHE
Completeness of non-normalizable modes
We establish the completeness of some characteristic sets of non-normalizable
modes by constructing fully localized square steps out of them, with each such
construction expressly displaying the Gibbs phenomenon associated with trying
to use a complete basis of modes to fit functions with discontinuous edges. As
well as being of interest in and of itself, our study is also of interest to
the recently introduced large extra dimension brane-localized gravity program
of Randall and Sundrum, since the particular non-normalizable mode bases that
we consider (specifically the irregular Bessel functions and the associated
Legendre functions of the second kind) are associated with the tensor
gravitational fluctuations which occur in those specific brane worlds in which
the embedding of a maximally four-symmetric brane in a five-dimensional anti-de
Sitter bulk leads to a warp factor which is divergent. Since the brane-world
massless four-dimensional graviton has a divergent wave function in these
particular cases, its resulting lack of normalizability is thus not seen to be
any impediment to its belonging to a complete basis of modes, and consequently
its lack of normalizability should not be seen as a criterion for not including
it in the spectrum of observable modes. Moreover, because the divergent modes
we consider form complete bases, we can even construct propagators out of them
in which these modes appear as poles with residues which are expressly finite.
Thus even though normalizable modes appear in propagators with residues which
are given as their finite normalization constants, non-normalizable modes can
just as equally appear in propagators with finite residues too -- it is just
that such residues will not be associated with bilinear integrals of the modes.Comment: 34 pages, 6 figures. Revte
Bubbling Geometries for Half BPS Wilson lines
We consider the supergravity backgrounds that correspond to supersymmetric
Wilson line operators in the context of AdS/CFT correspondence. We study the
gravitino and dilatino conditions of the IIB supergravity under the appropriate
ansatz, and obtain some necessary conditions for a supergravity background that
preserves the same symmetry as the supersymmetric Wilson lines. The
supergravity solutions are characterized by continuous version of maya
diagrams. This diagram is related to the eigenvalue distribution of the
Gaussian matrix model. We also consider the similar backgrounds of the
11-dimensional supergravity.Comment: 25 pages, 9 figures. v2:typos corrected. v3:added the differential
conditions and comments at the end of section 2. typos correcte
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