3,862 research outputs found
Universal fermionic spectral functions from string theory
We carry out the first holographic calculation of a fermionic response
function for a strongly coupled system with an explicit D=10 or D=11
supergravity dual. By considering the supersymmetry current, we obtain a
universal result applicable to all d=3 N=2 SCFTs with such duals. Surprisingly,
the spectral function does not exhibit a Fermi surface, despite the fact that
the system is at finite charge density. We show that it has a phonino pole and
at low frequencies there is a depletion of spectral weight with a power-law
scaling which is governed by a locally quantum critical point.Comment: 5 pages. Content the same, but significant change of presentation.
Version to be published in Phys. Rev. Let
Fivebranes Wrapped on SLAG Three-Cycles and Related Geometry
We construct ten-dimensional supergravity solutions corresponding to the near
horizon limit of IIB fivebranes wrapping special Lagrangian three-cycles of
constant curvature. The case of branes wrapping a three-sphere provides a
gravity dual of pure N=2 super-Yang-Mills theory in D=3. The non-trivial part
of the solutions are seven manifolds that admit two G_2 structures each of
which is covariantly constant with respect to a different connection with
torsion. We derive a formula for the generalised calibration for this general
class of solutions. We discuss analogous aspects of the geometry that arises
when fivebranes wrap other supersymmetric cycles which lead to Spin(7) and
SU(N) structures. In some cases there are two covariantly constant structures
and in others one.Comment: v2: 26 pages, 3 figures, 1 table. Section 7 slightly expanded,
references adde
Supersymmetric AdS Backgrounds in String and M-theory
We first present a short review of general supersymmetric compactifications
in string and M-theory using the language of G-structures and intrinsic
torsion. We then summarize recent work on the generic conditions for
supersymmetric AdS_5 backgrounds in M-theory and the construction of classes of
new solutions. Turning to AdS_5 compactifications in type IIB, we summarize the
construction of an infinite class of new Sasaki-Einstein manifolds in dimension
2k+3 given a positive curvature Kahler-Einstein base manifold in dimension 2k.
For k=1 these describe new supergravity duals for N=1 superconformal field
theories with both rational and irrational R-charges and central charge. We
also present a generalization of this construction, that has not appeared
elsewhere in the literature, to the case where the base is a product of
Kahler-Einstein manifolds.Comment: LaTeX, 35 pages, to appear in the proceedings of the 73rd Meeting
between Physicists and Mathematicians "(A)dS/CFT correspondence", Strasbourg,
September 11-13, 200
Sasaki-Einstein Metrics on S^2 x S^3
We present a countably infinite number of new explicit co-homogeneity one
Sasaki-Einstein metrics on S^2 x S^3, in both the quasi-regular and irregular
classes. These give rise to new solutions of type IIB supergravity which are
expected to be dual to N=1 superconformal field theories in four-dimensions
with compact or non-compact R-symmetry and rational or irrational central
charges, respectively.Comment: 20 pages. v2: references added, typos corrected. v3: minor typos
correcte
A New Infinite Class of Sasaki-Einstein Manifolds
We show that for every positive curvature Kahler-Einstein manifold in
dimension 2n there is a countably infinite class of associated Sasaki-Einstein
manifolds X_{2n+3} in dimension 2n+3. When n=1 we recover a recently discovered
family of supersymmetric AdS_5 x X_5 solutions of type IIB string theory, while
when n=2 we obtain new supersymmetric AdS_4 x X_7 solutions of D=11
supergravity. Both are expected to provide new supergravity duals of
superconformal field theories.Comment: 12 pages. v2: minor typos corrected, comment on generalisation to
product base manifold
Mechano-Magnetic Telemetry For Urban Infrastructure Monitoring
Many cities seek utilities monitoring with centrally managed Internet of Things (IoT) systems. This requires the development of numerous reliable low-cost wireless sensors, such as water temperature and flow meters, that can transmit information from subterranean pipes to surface-mounted receivers. Traditional radio communication systems are either unable to penetrate through multiple feet of earthen and manmade material, or have impractically large energy requirements which necessitate either frequent replacement of batteries, or a complex (and expensive) built-in energy harvesting system. Magnetic signaling systems do not suffer from this drawback: low-frequency electromagnetic waves have been shown to penetrate well through several feet of earth and water. In the past, these signals were too weak for practical use; however, this has changed with the recent proliferation of high-sensitivity magnetometers and compact rare-earth magnets.
A permanent magnet can be either rotated or vibrated to create an oscillating magnetic field. Utilizing this phenomenon, two types of magnetic transmitter are investigated in this study: one which uses a propeller to directly rotate a diametrically magnetized neodymium magnet; and a second in which a permanent magnet is oscillated back-and-forth across a novel soft-magnet Y-stator, which projects a switching magnetic field. In principle, these oscillating magnetic fields can be used for communication from subterranean infrastructure sensors—such as flow meters and leak detection devices—to an aboveground long range (LoRa) radio-networked Arduino receiver equipped with a magnetometer. Simulation software models the oscillating electromagnetic fields produced by the Y-stator configuration. Laboratory performance and field tests establish the capability of two IoT-linked leak-detection sensors that use magnetic telemetry. Remote datalogging demonstrates the viability of integrating many sensors and surface receivers into a single LoRa wireless IoT network
Molecular cloning, nucleotide sequencing, and construction of a Pasteurella haemolytica biotype A serotype 2 aroA mutant
http://www.worldcat.org/oclc/3846996
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