40,312 research outputs found
Evolving Network With Different Edges
We proposed an evolving network model constituted by the same nodes but
different edges. The competition between nodes and different links were
introduced. Scale free properties have been found in this model by continuum
theory. Different network topologies can be generated by some tunable
parameters. Simulation results consolidate the prediction.Comment: 14 pages, 9 figures, some contents revised, fluctuation of x degree
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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
[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
Effects of Capping on the (Ga,Mn)As Magnetic Depth Profile
Annealing can increase the Curie temperature and net magnetization in
uncapped (Ga,Mn)As films, effects that are suppressed when the films are capped
with GaAs. Previous polarized neutron reflectometry (PNR) studies of uncapped
(Ga,Mn)As revealed a pronounced magnetization gradient that was reduced after
annealing. We have extended this study to (Ga,Mn)As capped with GaAs. We
observe no increase in Curie temperature or net magnetization upon annealing.
Furthermore, PNR measurements indicate that annealing produces minimal
differences in the depth-dependent magnetization, as both as-grown and annealed
films feature a significant magnetization gradient. These results suggest that
the GaAs cap inhibits redistribution of interstitial Mn impurities during
annealing.Comment: 12 pages, 3 figures, submitted to Applied Physics Letter
Stochastic Physics, Complex Systems and Biology
In complex systems, the interplay between nonlinear and stochastic dynamics,
e.g., J. Monod's necessity and chance, gives rise to an evolutionary process in
Darwinian sense, in terms of discrete jumps among attractors, with punctuated
equilibrium, spontaneous random "mutations" and "adaptations". On an
evlutionary time scale it produces sustainable diversity among individuals in a
homogeneous population rather than convergence as usually predicted by a
deterministic dynamics. The emergent discrete states in such a system, i.e.,
attractors, have natural robustness against both internal and external
perturbations. Phenotypic states of a biological cell, a mesoscopic nonlinear
stochastic open biochemical system, could be understood through such a
perspective.Comment: 10 page
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
A Kind of Affine Weighted Moment Invariants
A new kind of geometric invariants is proposed in this paper, which is called
affine weighted moment invariant (AWMI). By combination of local affine
differential invariants and a framework of global integral, they can more
effectively extract features of images and help to increase the number of
low-order invariants and to decrease the calculating cost. The experimental
results show that AWMIs have good stability and distinguishability and achieve
better results in image retrieval than traditional moment invariants. An
extension to 3D is straightforward
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