15,546 research outputs found
Joint CLT for several random sesquilinear forms with applications to large-dimensional spiked population models
published_or_final_versio
Excitation Energy as a Basic Variable to Control Nuclear Disassembly
Thermodynamical features of Xe system is investigated as functions of
temperature and freeze-out density in the frame of lattice gas model. The
calculation shows different temperature dependence of physical observables at
different freeze-out density. In this case, the critical temperature when the
phase transition takes place depends on the freeze-out density. However, a
unique critical excitation energy reveals regardless of freeze-out density when
the excitation energy is used as a variable insteading of temperature.
Moreover, the different behavior of other physical observables with temperature
due to different vanishes when excitation energy replaces temperature.
It indicates that the excitation energy can be seen as a more basic quantity to
control nuclear disassembly.Comment: 3 pages, 2 figures, Revte
A Chandra ACIS view of the Thermal Composite Supernova Remnant 3C391
We present a 60 ks Chandra ACIS-S observation of the thermal composite
supernova remnant 3C391. The southeast-northwest elongated morphology is
similar to that previously found in radio and X-ray studies. This observation
unveils a highly clumpy structure of the remnant. Detailed spatially resolved
spectral analysis for the small-scale features reveals that the interior gas is
generally of normal metal abundance and has approached or basically reached
ionization equilibrium. The hydrogen column density increases from southeast to
northwest. Three mechanisms, radiative rim, thermal conduction, and cloudlet
evaporation, may all play roles in the X-ray appearance of 3C391 as a "thermal
composite" remnant, but there are difficulties with each of them in explaining
some physical properties. Comparatively, the cloudlet evaporation model is
favored by the main characteristics such as the highly clumpy structure and the
uniform temperature and density distribution over most of the remnant. The
directly measured postshock temperature also implies a young age, about 4 kyr,
for the remnant. The postshock gas pressure derived from the NE and SW rims,
which harbor maser spots, is consistent with the estimate for the maser
regions. An unresolved X-ray source is observed on the northwest border and its
spectrum is best fitted by a power-law.Comment: aastex, 27 pages (including 4 figures), to appear in the ApJ 1 Dec.
2004, v616 issu
Quantum lattice fluctuations in a model electron-phonon system
An analytical approach, based on the unitary transformation method, has been
developed to study the effect of quantum lattice fluctuations on the ground
state of a model electron-phonon system. To study nonadiabatic case, the
Green's function method is used to implement the perturbation treatment. The
phase diagram and the density of states of fermions are obtained. We show that
when electron-phonon coupling constant decreases or phonon
frequency increases the lattice dimerization and the gap in the
fermion spectrum decrease gradually. At some critical value the system becomes
gapless and the lattice dimerization disappears. The inverse-square-root
singularity of the density of states at the gap edge in the adiabatic case
disappears because of the nonadiabatic effect, which is consistent with the
measurement of optical conductivity in quasi-one-dimensional systems.Comment: 9 pages, 4 ps figures include
Quantifying solar superactive regions with vector magnetic field observations
The vector magnetic field characteristics of superactive regions (SARs) hold
the key for understanding why SARs are extremely active and provide the
guidance in space weather prediction. We aim to quantify the characteristics of
SARs using the vector magnetograms taken by the Solar Magnetic Field Telescope
at Huairou Solar Observatory Station. The vector magnetic field characteristics
of 14 SARs in solar cycles 22 and 23 were analyzed using the following four
parameters: 1) the magnetic flux imbalance between opposite polarities, 2) the
total photospheric free magnetic energy, 3) the length of the magnetic neutral
line with its steep horizontal magnetic gradient, and 4) the area with strong
magnetic shear. Furthermore, we selected another eight large and inactive
active regions (ARs), which are called fallow ARs (FARs), to compare them with
the SARs. We found that most of the SARs have a net magnetic flux higher than
7.0\times10^21 Mx, a total photospheric free magnetic energy higher than
1.0\times10^24 erg/cm, a magnetic neutral line with a steep horizontal magnetic
gradient (\geq 300 G/Mm) longer than 30 Mm, and an area with strong magnetic
shear (shear angle \geq 80\degree) greater than 100 Mm^2. In contrast, the
values of these parameters for the FARs are mostly very low. The Pearson
\c{hi}2 test was used to examine the significance of the difference between the
SARs and FARs, and the results indicate that these two types of ARs can be
fairly distinguished by each of these parameters. The significance levels are
99.55%, 99.98%, 99.98%, and 99.96%, respectively. However, no single parameter
can distinguish them perfectly. Therefore we propose a composite index based on
these parameters, and find that the distinction between the two types of ARs is
also significant with a significance level of 99.96%. These results are useful
for a better physical understanding of the SAR and FARComment: 9 pages, 3 figures, 2 table
Reply to "Comment on 'Fano resonance for Anderson Impurity Systems' "
In a recent Comment, Kolf et al. (cond-mat/0503669) state that our analysis
of the Fano resonance for Anderson impurity systems [Luo et al., Phys. Rev.
Lett 92, 256602 (2004)] is incorrect. Here we want to point out that their
comments are not based on firm physical results and their criticisms are
unjustified and invalid.Comment: 1 page, 1 figure, to appear in PR
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