399,253 research outputs found
The Galactic distribution of magnetic fields in molecular clouds and HII regions
{Magnetic fields exist on all scales in our Galaxy. There is a controversy
about whether the magnetic fields in molecular clouds are preserved from the
permeated magnetic fields in the interstellar medium (ISM) during cloud
formation. We investigate this controversy using available data in the light of
the newly revealed magnetic field structure of the Galactic disk obtained from
pulsar rotation measures (RMs).} % {We collected measurements of the magnetic
fields in molecular clouds, including Zeeman splitting data of OH masers in
clouds and OH or HI absorption or emission lines of clouds themselves.} % {The
Zeeman data show structures in the sign distribution of the line-of-sight
component of the magnetic field. Compared to the large-scale Galactic magnetic
fields derived from pulsar RMs, the sign distribution of the Zeeman data shows
similar large-scale field reversals. Previous such examinations were flawed in
the over-simplified global model used for the large-scale magnetic fields in
the Galactic disk.} % {We conclude that the magnetic fields in the clouds may
still ``remember'' the directions of magnetic fields in the Galactic ISM to
some extent, and could be used as complementary tracers of the large-scale
magnetic structure. More Zeeman data of OH masers in widely distributed clouds
are required.}Comment: Typo fixed in this new versio
Analytic continuation of single-particle resonance energy and wave function in relativistic mean field theory
Single-particle resonant states in spherical nuclei are studied by an
analytic continuation in the coupling constant (ACCC) method within the
framework of the self-consistent relativistic mean field (RMF) theory. Taking
the neutron resonant state in Ca as an example, we
examine the analyticity of the eigenvalue and eigenfunction for the Dirac
equation with respect to the coupling constant by means of a \pade
approximant of the second kind. The RMF-ACCC approach is then applied to
Zr and, for the first time, this approach is employed to investigate
both the energies, widths and wave functions for resonant states close
to the continuum threshold. Predictions are also compared with corresponding
results obtained from the scattering phase shift method.Comment: 19 pages, 9 figure
The Chinese-French SVOM mission for Gamma-Ray Burst studies
We present the Space-based multi-band astronomical Variable Objects Monitor
mission (SVOM) decided by the Chinese National Space Agency (CNSA) and the
French Space Agency (CNES). The mission which is designed to detect about 80
Gamma-Ray Bursts (GRBs) of all known types per year, will carry a very
innovative scientific payload combining a gamma-ray coded mask imagers
sensitive in the range 4 keV to 250 keV, a soft X-ray telescope operating
between 0.5 to 2 keV, a gamma-ray spectro-photometer sensitive in the range 50
keV to 5 MeV, and an optical telescope able to measure the GRB afterglow
emission down to a magnitude limit M with a 300 s exposure. A particular
attention will be also paid to the follow-up in making easy the observation of
the SVOM detected GRB by the largest ground based telescopes.
Scheduled for a launch in 2013, it will provide fast and reliable GRB
positions, will measure the broadband spectral energy distribution and temporal
properties of the prompt emission, and will quickly identify the optical
afterglows of detected GRBs, including those at very high redshift.Comment: Proceedings of the SF2A conference, Paris, 200
Switching speed distribution of spin-torque-induced magnetic reversal
The switching probability of a single-domain ferromagnet under spin-current
excitation is evaluated using the Fokker-Planck equation(FPE). In the case of
uniaxial anisotropy, the FPE reduces to an ordinary differential equation in
which the lowest eigenvalue determines the slowest switching
events. We have calculated by using both analytical and numerical
methods. It is found that the previous model based on thermally distributed
initial magnetization states \cite{Sun1} can be accurately justified in some
useful limiting conditions.Comment: The 10th Joint MMM/Intermag, HA-0
Multi chiral-doublets in one single nucleus
Adiabatic and configuration-fixed constraint triaxial relativistic mean field
(RMF) approaches are developed for the first time and a new phenomenon, the
existence of multi chiral-doublets (MD), i.e., more than one pairs of
chiral doublets bands in one single nucleus, is suggested for nuclei in A~100
region, typically for Rh, based on the triaxial deformations together
with their corresponding proton and neutron configurations.Comment: 10 pages, 4 figure
Grand Unified Yukawa Matrix Ansatz: The Standard Model Fermion Mass, Quark Mixing and CP Violation Parameters
We propose a new mass matrix ansatz: At the grand unified (GU) scale, the
standard model (SM) Yukawa coupling matrix elements are integer powers of the
square root of the GU gauge coupling constant \varepsilon \equiv
\sqrt{\alpha_{\text{GU}}}, multiplied by order unity random complex numbers. It
relates the hierarchy of the SM ermion masses and quark mixings to the gauge
coupling constants, greatly reducing the SM parameters, and can give good
fitting results of the SM fermion mass, quark mixing and CP violation
parameters. This is a neat but very effective ansatz.Comment: 4 pages (two columns), by REVTeX 4, 2 tables, no figures, version for
publication in CP
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