36,293 research outputs found
Dynamical quantum phase transitions in the dissipative Lipkin-Meshkov-Glick model and proposed realization in optical cavity QED
We present an optical cavity QED configuration that is described by a
dissipative version of the Lipkin-Meshkov-Glick model of an infinitely
coordinated spin system. This open quantum system exhibits both first- and
second-order non-equilibrium quantum phase transitions as a single, effective
field parameter is varied. Light emitted from the cavity offers measurable
signatures of the critical behavior, including that of the spin-spin
entanglement.Comment: 4 pages, 4 figures, typos corrected and other minor change
A comparative study of online news retrieval and presentation strategies
We introduce a news retrieval system on which we evaluated three alternative presentation strategies for online news retrieval. We used a user-oriented and task-oriented evaluation framework. The interfaces studied were Image, giving a grid of thumbnails for each story together with query-based summaries presented as tooltips, Summary, which displayed the summary information alongside each thumbnail, and Cluster, which grouped similar stories together and used the same display format as Image. The evaluation showed that the Summary Interface was preferred to the Image Interface, and that the Cluster Interface was helpful to users with a set task to complete. The implications of this study are also discussed in this paper
Drilling system design project 1967: final report of frame design committee
This report outlines the recommendations of the Frame
Design Committee for the final design of the machine, each
major part of the structure being considered individually
in the following sections :
1. Worktables
2. Guide and Slideways
3. Drill Head Support Structure
4. Swarf Disposal and Coolant Supply
5. General Constructio
Improved zinc oxide thermal control coatings
Ferricyanide/ferrocyanide couple prevents zinc oxide pigment degradation in thermal control coatings. Chemical couple retards physical optical property changes
Beaming effect from increased-index photonic crystal waveguides
We study the beaming effect of light for the case of increased-index photonic
crystal (PhC) waveguides, formed through the omission of low-dielectric media
in the waveguide region. We employ the finite-difference time-domain numerical
method for characterizing the beaming effect and determining the mechanisms of
loss and the overall efficiency of the directional emission. We find that,
while this type of PhC waveguides is capable of producing a highly collimated
emission as was demonstrated experimentally, the inherent characteristics of
the structure result in a restrictively low efficiency in the coupling of light
into the collimated beam of light.Comment: 4 pages, 5 figures, submitted to Applied Physics
Non-Simply-Connected Gauge Groups and Rational Points on Elliptic Curves
We consider the F-theory description of non-simply-connected gauge groups
appearing in the E8 x E8 heterotic string. The analysis is closely tied to the
arithmetic of torsion points on an elliptic curve. The general form of the
corresponding elliptic fibration is given for all finite subgroups of E8 which
are applicable in this context. We also study the closely-related question of
point-like instantons on a K3 surface whose holonomy is a finite group. As an
example we consider the case of the heterotic string on a K3 surface having the
E8 gauge symmetry broken to (E6 x SU(3))/Z3 or SU(9)/Z3 by point-like
instantons with Z3 holonomy.Comment: 15 pages, 2 embedded figures, some spurious U(1)'s remove
Animal models of Zika virus infection, pathogenesis, and immunity
Zika virus (ZIKV) is an emerging mosquito-transmitted flavivirus that now causes epidemics affecting millions of people on multiple continents. The virus has received global attention because of some of its unusual epidemiological and clinical features, including persistent infection in the male reproductive tract and sexual transmission, an ability to cross the placenta during pregnancy and infect the developing fetus to cause congenital malformations, and its association with Guillain-Barré syndrome in adults. This past year has witnessed an intensive effort by the global scientific community to understand the biology of ZIKV and to develop pathogenesis models for the rapid testing of possible countermeasures. Here, we review the recent advances in and utility and limitations of newly developed mouse and nonhuman primate models of ZIKV infection and pathogenesis
Tall sections from non-minimal transformations
In previous work, we have shown that elliptic fibrations with two sections,
or Mordell-Weil rank one, can always be mapped birationally to a Weierstrass
model of a certain form, namely, the Jacobian of a model.
Most constructions of elliptically fibered Calabi-Yau manifolds with two
sections have been carried out assuming that the image of this birational map
was a "minimal" Weierstrass model. In this paper, we show that for some
elliptically fibered Calabi-Yau manifolds with Mordell-Weil rank-one, the
Jacobian of the model is not minimal. Said another way,
starting from a Calabi-Yau Weierstrass model, the total space must be blown up
(thereby destroying the "Calabi-Yau" property) in order to embed the model into
. In particular, we show that the elliptic fibrations studied
recently by Klevers and Taylor fall into this class of models.Comment: 16 page
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