41,929 research outputs found
Possible discovery of the r-process characteristics in the abundances of metal-rich barium stars
We study the abundance distributions of a sample of metal-rich barium stars
provided by Pereira et al. (2011) to investigate the s- and r-process
nucleosynthesis in the metal-rich environment. We compared the theoretical
results predicted by a parametric model with the observed abundances of the
metal-rich barium stars. We found that six barium stars have a significant
r-process characteristic, and we divided the barium stars into two groups: the
r-rich barium stars (, [La/Nd]\,) and normal barium stars. The
behavior of the r-rich barium stars seems more like that of the metal-poor
r-rich and CEMP-r/s stars. We suggest that the most possible formation
mechanism for these stars is the s-process pollution, although their abundance
patterns can be fitted very well when the pre-enrichment hypothesis is
included. The fact that we can not explain them well using the s-process
nucleosynthesis alone may be due to our incomplete knowledge on the production
of Nd, Eu, and other relevant elements by the s-process in metal-rich and super
metal-rich environments (see details in Pereira et al. 2011).Comment: 5 pages, 5 figures, accepted for publication in A&
Light Fan Driven by a Relativistic Laser Pulse
When a relativistic laser pulse with a high photon density interacts with a specially tailored thin foil target, a strong torque is exerted on the resulting spiral-shaped foil plasma, or “light fan.” Because of its structure, the latter can gain significant orbital angular momentum (OAM), and the opposite OAM is imparted to the reflected light, creating a twisted relativistic light pulse. Such an interaction scenario is demonstrated by particle-in-cell simulation as well as analytical modeling, and should be easily verifiable in the laboratory. As an important characteristic, the twisted relativistic light pulse has a strong torque and ultrahigh OAM density
coupling constant
We calculate the coupling
using light cone QCD sum rule. Our result is
.Comment: RevTex, 5 pages + 1 PS figur
Loschmidt echo and fidelity decay near an exceptional point
Non-Hermitian classical and open quantum systems near an exceptional point
(EP) are known to undergo strong deviations in their dynamical behavior under
small perturbations or slow cycling of parameters as compared to Hermitian
systems. Such a strong sensitivity is at the heart of many interesting
phenomena and applications, such as the asymmetric breakdown of the adiabatic
theorem, enhanced sensing, non-Hermitian dynamical quantum phase transitions
and photonic catastrophe. Like for Hermitian systems, the sensitivity to
perturbations on the dynamical evolution can be captured by Loschmidt echo and
fidelity after imperfect time reversal or quench dynamics. Here we disclose a
rather counterintuitive phenomenon in certain non-Hermitian systems near an EP,
namely the deceleration (rather than acceleration) of the fidelity decay and
improved Loschmidt echo as compared to their Hermitian counterparts, despite
large (non-perturbative) deformation of the energy spectrum introduced by the
perturbations. This behavior is illustrated by considering the fidelity decay
and Loschmidt echo for the single-particle hopping dynamics on a tight-binding
lattice under an imaginary gauge field.Comment: 11 pages, 6 figures, to appear in Annalen der Physi
The sino-german 6cm polarization survey of the galactic plane: A summary
We have finished the 6cm polarization survey of the Galactic plane using the
Urumqi 25m radio telescope. It covers 10deg<l<230deg in Galactic longitude and
|b| <5deg in Galactic latitude. The new polarization maps not only reveal new
properties of the diffuse magnetized interstellar medium, but also are very
useful for studying individual objects such as Hii regions, which may act as
Faraday screens with strong regular magnetic fields inside, and supernova
remnants for their polarization properties and spectra. The high sensitivity of
the survey enables us to discover two new SNRs G178.2-4.2 and G25.3-2.1 and a
number of Hii regions.Comment: 10 pages, 1 figure. International Journal of Modern Physics:
Conference Series (IJMPCS) for Proceedings of 3rd Galileo-Xu Guangqi meetin
Observation of strong-coupling pairing with weakened Fermi-surface nesting at optimal hole doping in CaNaFeAs
We report an angle-resolved photoemission investigation of optimally-doped
CaNaFeAs. The Fermi surface topology of this compound
is similar to that of the well-studied BaKFeAs
material, except for larger hole pockets resulting from a higher hole
concentration per Fe atoms. We find that the quasi-nesting conditions are
weakened in this compound as compared to BaKFeAs. As
with BaKFeAs though, we observe nearly isotropic
superconducting gaps with Fermi surface-dependent magnitudes. A small variation
in the gap size along the momentum direction perpendicular to the surface is
found for one of the Fermi surfaces. Our superconducting gap results on all
Fermi surface sheets fit simultaneously very well to a global gap function
derived from a strong coupling approach, which contains only 2 global
parameters.Comment: 5 pages, 4 figure
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