5,407 research outputs found
Angular and Abundance Distribution of High-energy Gamma Rays and Neutrons Simulated by GEANT4 Code for Solar Flares
In the solar flare observed on June 3, 2012, high energy gamma-rays and
neutrons were observed. The event includes a remarkable feature of a high
neutron/gamma-ratio in the secondary particles. We have examined whether this
high n/-ratio can be explained by simulation. As a result of
simulations using the GEANT4 program, the high n/-ratio may be
reproduced for the case that helium and other heavy ions were dominantly
accelerated in the flare.Comment: submitted to the Proceeding of The 20th International Symposium on
Very High Energy Cosmic Ray Interaction (ISVHECRI 2018, Nagoya, Japan),
Europian Physics Journa
Effect of Impurities with Internal Structure on Multiband Superconductors - Possible Enhancement of Transition Temperature -
We study inelastic (dynamical) impurity scattering effects in two-band
superconductors with the same ( wave) or different ( wave) sign
order parameters. We focus on the enhancement of the superconducting transition
temperature by magnetic interband scattering with the interchange
of crystal-field singlet ground and multiplet excited states. Either the
-wave or -wave state is favored by the impurity-mediated
pairing, which depends on the magnetic and nonmagnetic scattering strengths
derived from the hybridization of the impurity states with the conduction
bands. The details are examined for the singlet-triplet configuration that is
suggestive of Pr impurities in the skutterudite superconductor
LaOsSb.Comment: 14 pages, 5 figures, to appear in J. Phys. Soc. Jpn. Vol. 79, No. 9
(2010
Phase diagram of orbital-selective Mott transitions at finite temperatures
Mott transitions in the two-orbital Hubbard model with different bandwidths
are investigated at finite temperatures. By means of the self-energy functional
approach, we discuss the stability of the intermediate phase with one orbital
localized and the other itinerant, which is caused by the orbital-selective
Mott transition (OSMT). It is shown that the OSMT realizes two different
coexistence regions at finite temperatures in accordance with the recent
results of Liebsch. We further find that the particularly interesting behavior
emerges around the special condition and J=0, which includes a new type
of the coexistence region with three distinct states. By systematically
changing the Hund coupling, we establish the global phase diagram to elucidate
the key role played by the Hund coupling on the Mott transitions.Comment: 4 pages, 6 figure
Relationships Between Wood Density and Annual Growth Rate Components in Balsam Fir (Abies Balsamea)
This study examined relationships of wood density components with annual growth rate components (or annual ring width components) in juvenile wood and mature wood of balsam fir [Abies balsamea (L.) Mill.]. The relationships were studied at two different levels: 1) inter-tree level (between trees), and 2) intra-tree level (within a tree). In addition, juvenile-mature wood correlations for these characteristics were investigated. Wood density and annual ring width components of individual growth rings were measured by X-ray densitometry. Based on tree averages (at the inter-tree level), wood density is significantly correlated with its components (earlywood density, latewood density) and latewood percentage in both juvenile wood and mature wood; and earlywood density and latewood percentage are the two most important parameters in determining the overall wood density of the tree. Wood density, however, is not significantly correlated with annual growth rate (ring width) in either juvenile wood or mature wood, although a weakly negative correlation tends to strengthen in mature wood. This suggests that the relationship between wood density and annual growth rate in this species may vary with cambial age. Intra-ring wood density variation (IDV) shows a positive correlation with wood density traits, latewood width, and latewood percentage in both juvenile wood and mature wood, whereas a weakly negative correlation of IDV with ring width and earlywood width exists in balsam fir. Latewood traits are the most important parameters in determining the intra-ring wood density uniformity. At the intra-tree level (based on ring averages within a tree), relationships between wood density components and ring width components are similar to those found between the trees, although some relationships, to some extent, vary with tree. For each wood density trait, the juvenile-mature wood correlation is significant but moderate. For this species, earlywood density in juvenile wood seems to be the best parameter for predicting mature wood density
Orbital-selective Mott transitions in the degenerate Hubbard model
We investigate the Mott transitions in two-band Hubbard models with different
bandwidths. Applying dynamical mean field theory, we discuss the stability of
itinerant quasi-particle states in each band. We demonstrate that separate Mott
transitions occur at different Coulomb interaction strengths in general, which
merge to a single transition only under special conditions. This kind of
behavior may be relevant for the physics of the single-layer ruthenates,
CaSrRuO.Comment: 4 pages, 4 figure
Measurement by FIB on the ISS: Two Emissions of Solar Neutrons Detected?
A new type of solar neutron detector (FIB) was launched onboard the Space
Shuttle Endeavour on July 16, 2009, and it began collecting data at the
International Space Station (ISS) on August 25, 2009. This paper summarizes the
three years of observations obtained by the solar neutron detector FIB until
the end of July 2012. The solar neutron detector FIB can determine both the
energy and arrival direction of neutrons. We measured the energy spectra of
background neutrons over the SAA region and elsewhere, and found the typical
trigger rates to be 20 counts/sec and 0.22 counts/sec, respectively. It is
possible to identify solar neutrons to within a level of 0.028 counts/sec,
provided that directional information is applied. Solar neutrons were observed
in association with the M-class solar flares that occurred on March 7 (M3.7)
and June 7 (M2.5) of 2011. This marked the first time that neutrons were
observed in M-class solar flares. A possible interpretaion of the prodcution
process is provided.Comment: 36 pages, 16 figures, and 3 Tables; Advanced in Astronmy, 2012,
Special issue on Cosmic Ray Variablity:Century of Its Obseravtion
First-order quantum phase transition in the orthogonal-dimer spin chain
We investigate the low-energy properties of the orthogonal-dimer spin chain
characterized by a frustrated dimer-plaquette structure. When the competing
antiferromagnetic couplings are varied, the first-order quantum phase
transition occurs between the dimer and the plaquette phases, which is
accompanied by nontrivial features due to frustration: besides the
discontinuity in the lowest excitation gap at the transition point, a sharp
level-crossing occurs for the spectrum in the plaquette phase. We further
reveal that the plateau in the magnetization curve at 1/4 of the full moment
dramatically changes its character in the vicinity of the critical point. It is
argued that the first-order phase transition in this system captures some
essential properties found in the two-dimensional orthogonal-dimer model
proposed for .Comment: 7 pages, submitted to Phys. Rev.
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