34,915 research outputs found
[Colored solutions of Yang-Baxter equation from representations of U_{q}gl(2)]
We study the Hopf algebra structure and the highest weight representation of
a multiparameter version of . The commutation relations as well as
other Hopf algebra maps are explicitly given. We show that the multiparameter
universal matrix can be constructed directly as a quantum double
intertwiner, without using Reshetikhin's transformation. An interesting feature
automatically appears in the representation theory: it can be divided into two
types, one for generic , the other for being a root of unity. When
applying the representation theory to the multiparameter universal
matrix, the so called standard and nonstandard colored solutions of the Yang-Baxter equation is obtained.Comment: [14]pages, latex, no figure
Unveiling Su Aurigae in the near Infrared: New high spatial resolution results using Adaptive Optics
We present here new results on circumstellar nebulosity around SU Aurigae, a
T-Tauri star of about 2 solar mass and 5 Myrs old at 152 pc in the J, H and K
bands using high resolution adaptive optics imaging (0\farcs30) with the Penn
state IR Imaging Spectrograph (PIRIS) at the 100 inch Mt. Wilson telescope.
A comparison with HST STIS optical (0.2 to 1.1 micron) images shows that the
orientation of the circumstellar nebulosity in the near-IR extends from PAs 210
to 270 degrees in H and K bands and up to 300 degrees in the J band. We call
the circumstellar nebulosity seen between 210 to 270 degrees as 'IR
nebulosity'. We find that the IR nebulosity (which extends up to 3.5 arcsecs in
J band and 2.5 arcsecs in the K band) is due to scattered light from the
central star. The IR nebulosity is either a cavity formed by the stellar
outflows or part of the circumstellar disk. We present a schematic
3-dimensional geometrical model of the disk and jet of SU Aur based on STIS and
our near-IR observations. According to this model the IR nebulosity is a part
of the circumstellar disk seen at high inclination angles. The extension of the
IR nebulosity is consistent with estimates of the disk diameter of 50 to 400 AU
in radius, from earlier mm, K band interferometric observations and SED
fittings.Comment: Accepted for publications in the Astronomical Journal, to appear in
the May issue of the Journa
DC-Prophet: Predicting Catastrophic Machine Failures in DataCenters
When will a server fail catastrophically in an industrial datacenter? Is it
possible to forecast these failures so preventive actions can be taken to
increase the reliability of a datacenter? To answer these questions, we have
studied what are probably the largest, publicly available datacenter traces,
containing more than 104 million events from 12,500 machines. Among these
samples, we observe and categorize three types of machine failures, all of
which are catastrophic and may lead to information loss, or even worse,
reliability degradation of a datacenter. We further propose a two-stage
framework-DC-Prophet-based on One-Class Support Vector Machine and Random
Forest. DC-Prophet extracts surprising patterns and accurately predicts the
next failure of a machine. Experimental results show that DC-Prophet achieves
an AUC of 0.93 in predicting the next machine failure, and a F3-score of 0.88
(out of 1). On average, DC-Prophet outperforms other classical machine learning
methods by 39.45% in F3-score.Comment: 13 pages, 5 figures, accepted by 2017 ECML PKD
Temporal and causal reasoning in deaf and hearing novice readers
Temporal and causal information in text are crucial in helping the reader form a coherent representation of a narrative. Deaf novice readers are generally poor at processing linguistic markers of causal/temporal information (i.e., connectives), but what is unclear is whether this is indicative of a more general deficit in reasoning about temporal/causal information. In Study 1, 10 deaf and 63 hearing children, matched for comprehension ability and age, were compared on a range of tasks tapping temporal/causal reasoning skills. In Study 2, 20 deaf and 32 hearing children, matched for age but not reading comprehension ability, were compared on revised versions of the tasks. The pattern of performance of the deaf was different from that of the hearing; they had difficulties when temporal and causal reasoning was text-based, but not when it was nonverbal, indicating that their global temporal/causal reasoning skills are comparable with those of their hearing counterparts
Elastic effects on relaxation volume tensor calculations
Relaxation volume tensors quantify the effect of stress on diffusion of
crystal defects. Continuum linear elasticity predicts that calculations of
these parameters using periodic boundary conditions do not suffer from
systematic deviations due to elastic image effects and should be independent of
supercell size or symmetry. In practice, however, calculations of formation
volume tensors of the interstitial in Stillinger-Weber silicon
demonstrate that changes in bonding at the defect affect the elastic moduli and
result in system-size dependent relaxation volumes. These vary with the inverse
of the system size. Knowing the rate of convergence permits accurate estimates
of these quantities from modestly sized calculations. Furthermore, within the
continuum linear elasticity assumptions the average stress can be used to
estimate the relaxation volume tensor from constant volume calculations.Comment: 31 pages, 6 figures, submitted to Phys. Rev.
First High Contrast Imaging Using a Gaussian Aperture Pupil Mask
Placing a pupil mask with a gaussian aperture into the optical train of
current telescopes represents a way to attain high contrast imaging that
potentially improves contrast by orders of magnitude compared to current
techniques. We present here the first observations ever using a gaussian
aperture pupil mask (GAPM) on the Penn State near-IR Imager and Spectrograph
(PIRIS) at the Mt. Wilson 100 telescope. Two nearby stars were
observed, Eridani and Her A. A faint companion was detected
around Her A, confirming it as a proper motion companion. Furthermore,
the observed H and K magnitudes of the companion were used to constrain its
nature. No companions or faint structure were observed for Eridani.
We found that our observations with the GAPM achieved contrast levels similar
to our coronographic images, without blocking light from the central star. The
mask's performance also nearly reached sensitivities reported for other ground
based adaptive optics coronographs and deep HST images, but did not reach
theoretically predicted contrast levels. We outline ways that could improve the
performance of the GAPM by an order of magnitude or more.Comment: 8 pages, 4 figures, accepted by ApJ letter
Long Range Interaction Models and Yangian Symmetry
The generalized Sutherland-Romer models and Yan models with internal spin
degrees are formulated in terms of the Polychronakos' approach and RTT relation
associated to the Yang-Baxter equation in consistent way. The Yangian symmetry
is shown to generate both models. We finally introduce the reflection algebra
K(u) to the long range models.Comment: 13 pages, preprint of Nankai Institute of Mathematics ( Theoretical
Physics Division ), published in Physical Review E of 1995. For hard copy,
write to Prof. Mo-lin GE directly. Do not send emails to this accoun
Entropy in the NUT-Kerr-Newman Black Holes Due to an Arbitrary Spin Field
Membrane method is used to compute the entropy of the NUT-Kerr-Newman black
holes. It is found that even though the Euler characteristic is greater than
two, the Bekenstein-Hawking area law is still satisfied. The formula relating the entropy and the Euler characteristic becomes inapplicable for
non-extreme four dimensional NUT-Kerr-Newman black holes
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