23,655 research outputs found
N=5 three-algebras and 5-graded Lie superalgebras
We discuss a generalization of N=6 three-algebras to N=5 three-algebras in
connection to anti-Lie triple systems and basic Lie superalgebras of type II.
We then show that the structure constants defined in anti-Lie triple systems
agree with those of N=5 superconformal theories in three dimensions.Comment: 15 pages, v3: typos corrected, references added, and published
versio
Land use/land cover mapping (1:25000) of Taiwan, Republic of China by automated multispectral interpretation of LANDSAT imagery
Three methods were tested for collection of the training sets needed to establish the spectral signatures of the land uses/land covers sought due to the difficulties of retrospective collection of representative ground control data. Computer preprocessing techniques applied to the digital images to improve the final classification results were geometric corrections, spectral band or image ratioing and statistical cleaning of the representative training sets. A minimal level of statistical verification was made based upon the comparisons between the airphoto estimates and the classification results. The verifications provided a further support to the selection of MSS band 5 and 7. It also indicated that the maximum likelihood ratioing technique can achieve more agreeable classification results with the airphoto estimates than the stepwise discriminant analysis
Mode-medium instability and its correction with a Gaussian reflectivity mirror
A high power CO2 laser beam is known to deteriorate after a few microseconds due to a mode-medium instability (MMI) which results from an intensity dependent heating rate related to the vibrational-to-translational decay of the upper and lower CO2 lasing levels. An iterative numerical technique is developed to model the time evolution of the beam as it is affected by the MMI. The technique is used to study the MMI in an unstable CO2 resonator with a hard-edge output mirror for different parameters like the Fresnel number and the gas density. The results show that the mode of the hard edge unstable resonator deteriorates because of the diffraction ripples in the mode. A Gaussian-reflectivity mirror was used to correct the MMI. This mirror produces a smoother intensity profile which significantly reduces the effects of the MMI. Quantitative results on peak density variation and beam quality are presented
From Linked Data to Relevant Data -- Time is the Essence
The Semantic Web initiative puts emphasis not primarily on putting data on
the Web, but rather on creating links in a way that both humans and machines
can explore the Web of data. When such users access the Web, they leave a trail
as Web servers maintain a history of requests. Web usage mining approaches have
been studied since the beginning of the Web given the log's huge potential for
purposes such as resource annotation, personalization, forecasting etc.
However, the impact of any such efforts has not really gone beyond generating
statistics detailing who, when, and how Web pages maintained by a Web server
were visited.Comment: 1st International Workshop on Usage Analysis and the Web of Data
(USEWOD2011) in the 20th International World Wide Web Conference (WWW2011),
Hyderabad, India, March 28th, 201
Tunneling between helical Majorana modes and helical Luttinger liquids
We propose and study the charge transport through single and double quantum
point contacts setup between helical Majorana modes and an interacting helical
Luttinger liquid. We show that the differential conductance decreases for
stronger repulsive interactions and that the point contacts become insulating
above a critical interaction strength. For a single point contact, the
differential conductance as a function of bias voltage shows a series of peaks
due to Andreev reflection of electrons in the Majorana modes. In the case of
two point contacts, interference phenomena make the structure of the individual
resonance peaks less universal and show modulations with different separation
distance between the contacts. For small separation distance the overall
features remain similar to the case of a single point contact.Comment: v.2: 14 pages, 11 figures; adding one figure, an appendix, and some
minor change
Enhanced damping of ion acoustic waves in dense plasmas
A theory for the ion acoustic wave damping in dense plasmas and warm dense
matter, accounting for the Umklapp process, is presented. A higher decay rate
compared to the prediction from the Landau damping theory is predicted for
high-Z dense plasmas where the electron density ranges from to and the electron temperature is moderately higher
than the Fermi energy
Non-equilibrium Transport in the Anderson model of a biased Quantum Dot: Scattering Bethe Ansatz Phenomenology
We derive the transport properties of a quantum dot subject to a source-drain
bias voltage at zero temperature and magnetic field. Using the Scattering Bethe
Anstaz, a generalization of the traditional Thermodynamic Bethe Ansatz to open
systems out of equilibrium, we derive exact results for the quantum dot
occupation out of equilibrium and, by introducing phenomenological spin- and
charge-fluctuation distribution functions in the computation of the current,
obtain the differential conductance for large U/\Gamma. The Hamiltonian to
describe the quantum dot system is the Anderson impurity Hamiltonian and the
current and dot occupation as a function of voltage are obtained numerically.
We also vary the gate voltage and study the transition from the mixed valence
to the Kondo regime in the presence of a non-equilibrium current. We conclude
with the difficulty we encounter in this model and possible way to solve them
without resorting to a phenomenological method.Comment: 20 pages, 20 figures, published versio
Theory of plasmon decay in dense plasmas and warm dense matter
The decay of the Langmuir waves in dense plasmas is not accurately predicted
by the prevalent Landau damping theory. A dielectric function theory is
introduced, predicting much higher damping than the Landau damping theory. This
strong damping is in better agreement with the experimentally observed data in
metals. It is shown that the strong plasmon decay leads to the existence of a
parameter regime where the backward Raman scattering is unstable while the
forward Raman scattering is stable. This regime may be used to create intense
x-ray pulses, by means of the the backward Raman compression. The optimal pulse
duration and intensity is estimated
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