1,267 research outputs found
Global Entanglement for Multipartite Quantum States
Based on the residual entanglement [9] (Phys. Rev. A \textbf{71}, 044301
(2005)), we present the global entanglement for a multipartite quantum state.
The measure is shown to be also obtained by the bipartite partitions of the
multipartite state. The distinct characteristic of the global entanglement is
that it consists of the sum of different entanglement contributions. The
measure can provide sufficient and necessary condition of fully separability
for pure states and be conveniently extended to mixed states by minimizing the
convex hull. To test the sufficiency of the measure for mixed states, we
evaluate the global entanglement of bound entangled states. The properties of
the measure discussed finally show the global entanglement is an entanglement
monotone.Comment: 6 page
Genuine tripartite entanglement monotone of dimensional systems
A genuine tripartite entanglement monotone is presented for -dimensional tripartite pure states by introducing a new
entanglement measure for bipartite pure states. As an application, we consider
the genuine tripartite entanglement of the ground state of the exactly solvable
isotropic spin-1/2 chain with three-spin interaction. It is shown that the
singular behavior of the genuine tripartite entanglement exactly signals a
quantum phase transition.Comment: 5 page
Investigation of passive flow control techniques to enhance the stall characteristics of a microlight aircraft
This report investigates the enhancement of aerodynamic stall characteristics of a Skyranger microlight aircraft by the use of passive flow control techniques, namely vortex generators and turbulators. Each flow control device is designed and scaled to application conditions. Force balance measurements and surface oil flow visualisation are carried out on a half-model of the microlight to further investigate the nature of the flow on the aircraft with and without the flow control devices. The results indicate a clear advantage to the use of turbulators compared with vortex generators. Turbulators increased the maximum lift coefficient by 2.8%, delayed the onset of stall by increasing the critical angle by 17.6% and reduced the drag penalty at both lower (pre-stall) and higher angles of attack by 8% compared to vortex generators. With vortex generators applied, the results indicated a delayed stall with an increase in the critical angle by 2% and a reduced drag penalty at higher angles of attack
Resources and student achievement – evidence from a Swedish policy reform
This paper utilizes a policy change to estimate the effect of teacher density on student performance. We find that an increase in teacher density has a positive effect on student achievement. The baseline estimate – obtained by using the grade point average as the outcome variable – implies that resource increases corresponding to the class-size reduction in the STAR-experiment (i.e., a reduction of 7 students) improves performance by 2.6 percentile ranks (or 0.08 standard deviations). When we use test score data for men, potentially a more objective measure of student performance, the effect of resources appears to be twice the size of the baseline estimate.Student performance; teacher/student ratio; policy reform; differences-in-differences
Abc3-Mediated Efflux of an Endogenous Digoxin-like Steroidal Glycoside by Magnaporthe oryzae Is Necessary for Host Invasion during Blast Disease
10.1371/journal.ppat.1002888PLoS Pathogens88
On the Conductance Sum Rule for the Hierarchical Edge States of the Fractional Quantum Hall Effect
The conductance sum rule for the hierarchical edge channel currents of a
Fractional Quantum Hall Effect state is derived analytically within the
Haldane-Halperin hierarchy scheme. We provide also an intuitive interpretation
for the hierarchical drift velocities of the edge excitations.Comment: 11 pages, no figure, Revtex 3.0, IC/93/329, ASITP-93-5
Measurement of Surface Machining Damage in Ceramics
Machining damage in hot pressed (NCI32) silicon nitride, due to surface grinding and polishing, has been simulated by dragging a Knoop indentor across the surface of optically polished samples. The reflection coefficient of the cracks thus generated was measured versus frequency, and was found to be in excellent agreement with the theoretical calculations of Achenbach and Brind1. We found that the long slot-like cracks were closed at the top (about 20% of the total crack depth), which was due to the residual stress introduced when the samples were scratched. By taking into consideration the crack closure, and with the results of our scattering measurements, we were able to make failure stress predictions with an accuracy of better than 10%
Internal friction and Jahn-Teller effect in the charge-ordered La1-xCaxMnO3 (0.5<x<0.87)
The Jahn-Teller effect in the charge-ordered (CO) state for La1-xCaxMnO3
(0.5<x<0.87) was studied by measuring the low-temperature powder x-ray
diffraction, internal friction, and shear modulus. We find that the
electron-lattice interaction with the static Jahn-Teller distortion is the
strongest near x=0.75 in the CO state. It was particularly observed that a
crossover of the Jahn-Teller vibration mode from Q2 to Q3 near x=0.75 induces
crossovers of the crystal structure from tetragonally compressed to
tetragonally elongated orthorhombic, and of the magnetic structure from CE-type
to C-type near x=0.75. The experimental results give strong evidence that the
Jahn-Teller effect not only plays a key role in stabilizing the CO state, but
also determines the magnetic and crystal structures in the CO state for
La1-xCaxMnO3.Comment: 13 pages, 3 figures, PD
ac Josephson effect in the resonant tunneling through mesoscopic superconducting junctions
We investigate ac Josephson effect in the resonant tunneling through
mesoscopic superconducting junctions. In the presence of microwave irradiation,
we show that the trajectory of multiple Andreev reflections can be closed by
emitting or absorbing photons. Consequently, photon-assisted Andreev states are
formed and play the role of carrying supercurrent. On the Shapiro steps, dc
component appears when the resonant level is near a series of positions with
spacing of half of the microwave frequency. Analytical result is derived in the
limit of infinite superconducting gap, based on which new features of ac
Josephson effect are revealed.Comment: 11 pages, 3 figure
Intense duskside lower band chorus waves observed by Van Allen Probes: Generation and potential acceleration effect on radiation belt electrons
Abstract Local acceleration driven by whistler mode chorus waves largely accounts for the enhancement of radiation belt relativistic electron fluxes, whose favored region is usually considered to be the plasmatrough with magnetic local time approximately from midnight through dawn to noon. On 2 October 2013, the Van Allen Probes recorded a rarely reported event of intense duskside lower band chorus waves (with power spectral density up to 10-3nT 2/Hz) in the low-latitude region outside of L=5. Such chorus waves are found to be generated by the substorm-injected anisotropic suprathermal electrons and have a potentially strong acceleration effect on the radiation belt energetic electrons. This event study demonstrates the possibility of broader spatial regions with effective electron acceleration by chorus waves than previously expected. For such intense duskside chorus waves, the occurrence probability, the preferential excitation conditions, the time duration, and the accurate contribution to the long-term evolution of radiation belt electron fluxes may need further investigations in future
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