33,076 research outputs found
Propagating wave in active region-loops, located over the solar disk observed by the Interface Region Imaging Spectrograph
We aim to ascertain the physical parameters of a propagating wave over the
solar disk detected by the Interface Region Imaging Spectrograph (IRIS). Using
imaging data from the IRIS and the Solar Dynamic Observatory (SDO), we tracked
bright spots to determine the parameters of a propagating transverse wave in
active region (AR) loops triggered by activation of a filament. Deriving the
Doppler velocity of Si IV line from spectral observations of IRIS, we have
determined the rotating directions of active region loops which are relevant to
the wave. On 2015 December 19, a filament was located on the polarity inversion
line of the NOAA AR 12470. The filament was activated and then caused a C 1.1
two-ribbon flare. Between the flare ribbons, two rotation motions of a set of
bright loops were observed to appear in turn with opposite directions.
Following the end of the second rotation, a propagating wave and an associated
transverse oscillation were detected in these bright loops. In 1400 A channel,
there was bright material flowing along the loops in a wave-like manner, with a
period of ~128 s and a mean amplitude of ~880 km. For the transverse
oscillation, we tracked a given loop and determine the transverse positions of
the tracking loop in a limited longitudinal range. In both of 1400 A and 171 A
channels, approximately four periods are distinguished during the transverse
oscillation. The mean period of the oscillation is estimated as ~143 s and the
displacement amplitude as between ~1370 km and ~690 km. We interpret these
oscillations as a propagating kink wave and obtain its speed of ~1400 km s-1.
Our observations reveal that a flare associated with filament activation could
trigger a kink propagating wave in active region loops over the solar disk.Comment: Accepted for publication in A&
q-deformed Supersymmetric t-J Model with a Boundary
The q-deformed supersymmetric t-J model on a semi-infinite lattice is
diagonalized by using the level-one vertex operators of the quantum affine
superalgebra . We give the bosonization of the boundary
states. We give an integral expression of the correlation functions of the
boundary model, and derive the difference equations which they satisfy.Comment: LaTex file 18 page
The Dynamical Yang-Baxter Relation and the Minimal Representation of the Elliptic Quantum Group
In this paper, we give the general forms of the minimal matrix (the
elements of the -matrix are numbers) associated with the Boltzmann
weights of the interaction-round-a-face (IRF) model and the minimal
representation of the series elliptic quantum group given by Felder
and Varchenko. The explicit dependence of elements of -matrices on spectral
parameter are given. They are of five different forms (A(1-4) and B). The
algebra for the coefficients (which do not depend on ) are given. The
algebra of form A is proved to be trivial, while that of form B obey
Yang-Baxter equation (YBE). We also give the PBW base and the centers for the
algebra of form B.Comment: 23 page
Note on the Algebra of Screening Currents for the Quantum Deformed W-Algebra
With slight modifications in the zero modes contributions, the positive and
negative screening currents for the quantum deformed W-algebra W_{q,p}(g) can
be put together to form a single algebra which can be regarded as an elliptic
deformation of the universal enveloping algebra of \hat{g}, where g is any
classical simply-laced Lie algebra.Comment: LaTeX file, 9 pages. Errors in Serre relation corrected. Two
references to Awata,H. et al adde
Window on Higgs Boson: Fourth Generation Decays Revisited
Direct and indirect searches of the Higgs boson suggest that 113 GeV
170 GeV is likely. With the LEP era over and the
Tevatron Run II search via arduous, we revisit a case where
or jets could arise via strong pair
production. In contrast to 10 years ago, the tight electroweak constraint on
-- (hence --) splitting reduces FCNC
, rates, making naturally competitive.
Such a "cocktail solution" is precisely the mix that could evade the CDF search
for , and the may well be lurking below the top. In
light of the Higgs program, this two-in-one strategy should be pursued.Comment: 4 pages, RevTex, 4 eps figures, One more figure, version to be
published in Phys. Rev.
OVI, NV and CIV in the Galactic Halo: II. Velocity-Resolved Observations with Hubble and FUSE
We present a survey of NV and OVI (and where available CIV) in the Galactic
halo, using data from the Far Ultraviolet Spectroscopic Explorer (FUSE) and the
Hubble Space Telescope (HST) along 34 sightlines. These ions are usually
produced in nonequilibrium processes such as shocks, evaporative interfaces, or
rapidly cooling gas, and thus trace the dynamics of the interstellar medium.
Searching for global trends in integrated and velocity-resolved column density
ratios, we find large variations in most measures, with some evidence for a
systematic trend of higher ionization (lower NV/OVI column density ratio) at
larger positive line-of-sight velocities. The slopes of log[N(NV)/N(OVI)] per
unit velocity range from -0.015 to +0.005, with a mean of
-0.0032+/-0.0022(r)+/-0.0014(sys) dex/(km/s). We compare this dataset with
models of velocity-resolved high-ion signatures of several common physical
structures. The dispersion of the ratios, OVI/NV/CIV, supports the growing
belief that no single model can account for hot halo gas, and in fact some
models predict much stronger trends than are observed. It is important to
understand the signatures of different physical structures to interpret
specific lines of sight and future global surveys.Comment: ApJ in press 43 pages, 22 fig
Anti-shielding Effect and Negative Temperature in Instantaneously Reversed Electric Fields and Left-Handed Media
The connections between the anti-shielding effect, negative absolute
temperature and superluminal light propagation in both the instantaneously
reversed electric field and the left-handed media are considered in the present
paper. The instantaneous inversion of the exterior electric field may cause the
electric dipoles into the state of negative absolute temperature and therefore
give rise to a negative effective mass term of electromagnetic field (i. e.,
the electromagnetic field propagating inside the negative-temperature medium
will acquire an imaginary rest mass), which is said to result in the potential
superluminality effect of light propagation in this anti-shielding dielectric.
In left-handed media, such phenomena may also arise.Comment: 9 pages, Late
Coherent control of plasma dynamics
Coherent control of a system involves steering an interaction to a final
coherent state by controlling the phase of an applied field. Plasmas support
coherent wave structures that can be generated by intense laser fields. Here,
we demonstrate the coherent control of plasma dynamics in a laser wakefield
electron acceleration experiment. A genetic algorithm is implemented using a
deformable mirror with the electron beam signal as feedback, which allows a
heuristic search for the optimal wavefront under laser-plasma conditions that
is not known a priori. We are able to improve both the electron beam charge and
angular distribution by an order of magnitude. These improvements do not simply
correlate with having the `best' focal spot, since the highest quality vacuum
focal spot produces a greatly inferior electron beam, but instead correspond to
the particular laser phase that steers the plasma wave to a final state with
optimal accelerating fields
Detecting outliers with foreign patch interpolation
In medical imaging, outliers can contain hypo/hyper-intensities, minor deformations, or completely altered anatomy. To detect these irregularities it is helpful to learn the features present in both normal and abnormal images. However this is difficult because of the wide range of possible abnormalities and also the number of ways that normal anatomy can vary naturally. As such, we leverage the natural variations in normal anatomy to create a range of synthetic abnormalities. Specifically, the same patch region is extracted from two independent samples and replaced with an interpolation between both patches. The interpolation factor, patch size, and patch location are randomly sampled from uniform distributions. A wide residual encoder decoder is trained to give a pixel-wise prediction of the patch and its interpolation factor. This encourages the network to learn what features to expect normally and to identify where foreign patterns have been introduced. The estimate of the interpolation factor lends itself nicely to the derivation of an outlier score. Meanwhile the pixel-wise output allows for pixel- and subject- level predictions using the same model. Our code is available at https://github.com/jemtan/FP
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