204,659 research outputs found
Toward parton equilibration with improved parton interaction matrix elements
The Quark-Gluon Plasma can be produced in high energy heavy ion collisions
and how it equilibrates is important for the extraction of the properties of
strongly interacting matter. A radiative transport model can be used to reveal
interesting characteristics of Quark-Gluon Plasma thermalization. For example,
screened parton interactions always lead to partial pressure isotropization.
Systems with different initial pressure anisotropies evolve toward the same
asymptotic evolution. In particular, radiative processes are crucial for the
chemical equilibration of the system. Matrix elements under the soft and
collinear approximation for these processes, as first derived by Gunion and
Bertsch, are widely used. A different approach is to start with the exact
matrix elements for the two to three and its inverse processes. General
features of this approach will be reviewed and the results will be compared
with the Gunion-Bertsch results. We will comment on the possible implications
of the exact matrix element approach on Quark-Gluon Plasma thermalization.Comment: Presented at the 11th International Conference on Nucleus-Nucleus
Collisions (NN2012), San Antonio, Texas, USA, 27 May-1 June 201
Kilohertz QPO Frequency and Flux Decrease in AQL X-1 and Effect of Soft X-ray Spectral Components
We report on an RXTE/PCA observation of Aql X-1 during its outburst in March
1997 in which, immediately following a Type-I burst, the broad-band 2-10 keV
flux decreased by about 10% and the kilohertz QPO frequency decreased from
813+-3 Hz to 776+-4 Hz. This change in kHz QPO frequency is much larger than
expected from a simple extrapolation of a frequency-flux correlation
established using data before the burst. Meanwhile a very low frequency noise
(VLFN) component in the broad-band FFT power spectra with a fractional
root-mean-square (rms) amplitude of 1.2% before the burst ceased to exist after
the burst. All these changes were accompanied by a change in the energy
spectral shape. If we characterize the energy spectra with a model composed of
two blackbody (BB) components and a power law component, almost all the
decrease in flux was in the two BB components. We attribute the two BB
components to the contributions from a region very near the neutron star or
even the neutron star itself and from the accretion disk, respectively.Comment: 12 pages with 4 figures, accepted for publication in ApJ Letters,
typos corrected and references update
Dynamical coupled-channel study of K* K*bar and omega phi states in a chiral quark model
A dynamical coupled-channel study of K* K*bar state with isospin 0 and omega
phi state is performed within both the chiral SU(3) quark model and the
extended chiral SU(3) quark model by solving a resonating group method (RGM)
equation. The model parameters are taken from our previous work, which gave a
satisfactory description of the energies of the octet and decuplet baryon
ground states, the binding energy of the deuteron, the nucleon-nucleon (NN)
scattering phase shifts, and the hyperon-nucleon (YN) cross sections. The
results show that the interactions of K* K*bar states are attractive, which
consequently result in K* K*bar bound states with the binding energies of about
10-70 MeV, and contrarily, no omega phi bound state is obtained. The channel
coupling effect of K* K*bar and omega phi is found to be considerably large,
which makes the binding of K* K*bar 5-45 MeV deeper. The plausible
interpretation of f_0(1710) and X(1812) being K* K*bar dominated states is
briefly discussed.Comment: 7 pages, 4 figure
Photovoltage Detection of Edge Magnetoplasmon Oscillations and Giant Magnetoplasmon Resonances in A Two-Dimensional Hole System
In our high mobility p-type AlGaAs/GaAs two-dimensional hole samples, we
originally observe the B-periodic oscillation induced by microwave (MW) in
photovoltage (PV) measurements. In the frequency range of our measurements (5 -
40 GHz), the period ({\Delta}B) is inversely proportional to the microwave
frequency (f). The distinct oscillations come from the edge magnetoplasmon
(EMP) in the high quality heavy hole system. In our hole sample with a very
large effective mass, the observation of the EMP oscillations is in neither the
low frequency limit nor the high frequency limit, and the damping of the EMP
oscillations is very weak under high magnetic fields. Simultaneously, we
observe the giant plasmon resonance signals in our measurements on the shallow
two-dimensional hole system (2DHS)
A Research and Strategy of Remote Sensing Image Denoising Algorithms
Most raw data download from satellites are useless, resulting in transmission
waste, one solution is to process data directly on satellites, then only
transmit the processed results to the ground. Image processing is the main data
processing on satellites, in this paper, we focus on image denoising which is
the basic image processing. There are many high-performance denoising
approaches at present, however, most of them rely on advanced computing
resources or rich images on the ground. Considering the limited computing
resources of satellites and the characteristics of remote sensing images, we do
some research on these high-performance ground image denoising approaches and
compare them in simulation experiments to analyze whether they are suitable for
satellites. According to the analysis results, we propose two feasible image
denoising strategies for satellites based on satellite TianZhi-1.Comment: 9 pages, 4 figures, ICNC-FSKD 201
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