179,403 research outputs found
Black Box White Arrow
The present paper proposes a new and systematic approach to the so-called
black box group methods in computational group theory. Instead of a single
black box, we consider categories of black boxes and their morphisms. This
makes new classes of black box problems accessible. For example, we can enrich
black box groups by actions of outer automorphisms.
As an example of application of this technique, we construct Frobenius maps
on black box groups of untwisted Lie type in odd characteristic (Section 6) and
inverse-transpose automorphisms on black box groups encrypting .
One of the advantages of our approach is that it allows us to work in black
box groups over finite fields of big characteristic. Another advantage is
explanatory power of our methods; as an example, we explain Kantor's and
Kassabov's construction of an involution in black box groups encrypting .
Due to the nature of our work we also have to discuss a few methodological
issues of the black box group theory.
The paper is further development of our text "Fifty shades of black"
[arXiv:1308.2487], and repeats parts of it, but under a weaker axioms for black
box groups.Comment: arXiv admin note: substantial text overlap with arXiv:1308.248
Sunspot rotation, filament, and flare: The event on 2000 February 10
We find that a sunspot with positive polarity had an obvious
counter-clockwise rotation and resulted in the formation and eruption of an
inverse S-shaped filament in NOAA active region (AR) 08858 from 2000 February 9
to 10. The sunspot had two umbrae which rotated around each other by 195
degrees within about twenty-four hours. The average rotation rate was nearly 8
degrees per hour. The fastest rotation in the photosphere took place during
14:00UT to 22:01UT on February 9, with the rotation rate of nearly 16 degrees
per hour. The fastest rotation in the chromosphere and the corona took place
during 15:28UT to 19:00UT on February 9, with the rotation rate of nearly 20
degrees per hour. Interestingly, the rapid increase of the positive magnetic
flux just occurred during the fastest rotation of the rotating sunspot, the
bright loop-shaped structure and the filament. During the sunspot rotation, the
inverse S-shaped filament gradually formed in the EUV filament channel. The
filament experienced two eruptions. In the first eruption, the filament rose
quickly and then the filament loops carrying the cool and the hot material were
seen to spiral into the sunspot counterclockwise. About ten minutes later, the
filament became active and finally erupted. The filament eruption was
accompanied with a C-class flare and a halo coronal mass ejection (CME). These
results provide evidence that sunspot rotation plays an important role in the
formation and eruption of the sigmoidal active-region filament.Comment: 20 pages, 9 figures, Accepted for publication in Ap
Interchange reconnection associated with a confined filament eruption: Implications for the source of transient cold-dense plasma in solar winds
The cold-dense plasma is occasionally detected in the solar wind with in situ
data, but the source of the cold-dense plasma remains illusive. Interchange
reconnections (IRs) between closed fields and nearby open fields are well known
to contribute to the formation of solar winds. We present a confined filament
eruption associated with a puff-like coronal mass ejection (CME) on 2014
December 24. The filament underwent successive activations and finally erupted,
due to continuous magnetic flux cancellations and emergences. The confined
erupting filament showed a clear untwist motion, and most of the filament
material fell back. During the eruption, some tiny blobs escaped from the
confined filament body, along newly-formed open field lines rooted around the
south end of the filament, and some bright plasma flowed from the north end of
the filament to remote sites at nearby open fields. The newly-formed open field
lines shifted southward with multiple branches. The puff-like CME also showed
multiple bright fronts and a clear southward shift. All the results indicate an
intermittent IR existed between closed fields of the confined erupting filament
and nearby open fields, which released a portion of filament material (blobs)
to form the puff-like CME. We suggest that the IR provides a possible source of
cold-dense plasma in the solar wind
Comparison of Adaptive Optics Scanning Light Ophthalmoscopic Fluorescein Angiography and Offset Pinhole Imaging
Recent advances to the adaptive optics scanning light ophthalmoscope (AOSLO) have enabled finer in vivo assessment of the human retinal microvasculature. AOSLO confocal reflectance imaging has been coupled with oral fluorescein angiography (FA), enabling simultaneous acquisition of structural and perfusion images. AOSLO offset pinhole (OP) imaging combined with motion contrast post-processing techniques, are able to create a similar set of structural and perfusion images without the use of exogenous contrast agent. In this study, we evaluate the similarities and differences of the structural and perfusion images obtained by either method, in healthy control subjects and in patients with retinal vasculopathy including hypertensive retinopathy, diabetic retinopathy, and retinal vein occlusion. Our results show that AOSLO OP motion contrast provides perfusion maps comparable to those obtained with AOSLO FA, while AOSLO OP reflectance images provide additional information such as vessel wall fine structure not as readily visible in AOSLO confocal reflectance images. AOSLO OP offers a non-invasive alternative to AOSLO FA without the need for any exogenous contrast agent
Matrix product solution to an inhomogeneous multi-species TASEP
We study a multi-species exclusion process with inhomogeneous hopping rates.
This model is equivalent to a Markov chain on the symmetric group that
corresponds to a random walk in the affine braid arrangement. We find a matrix
product representation for the stationary state of this model. We also show
that it is equivalent to a graphical construction proposed by Ayyer and
Linusson, which generalizes Ferrari and Martin's construction
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