Importance of Prolate Neutrino Radiation in Core-Collapse Supernovae: The Reason for the Prolate Geometry of SN1987A?

We have carried out 2-D simulations of core-collapse supernova explosions. The local neutrino radiation field is assumed to have its maximum value either at the symmetry (polar) axis or on the equatorial plane. These lead to the prolate and oblate explosions, respectively. We find that the gain of the explosion energy in the prolate explosion evolves more predominately than that in the oblate one when the total neutrino luminosity is given. Namely, the prolate explosion is more energetic than the oblate one. One of the authors (Shimizu et al. 2001) showed for the first time that globally anisotropic neutrino radiation produces more powerful explosion than the spherical neutrino radiation does. In our previous study (Madokoro et al. 2003), we improved the numerical code of Shimizu et al. and demonstrated that the globally anisotropic neutrino radiation yields more energetic explosion than spatially-fluctuated neutrino radiation does. Together with the result of this paper, we conclude that the globally anisotropic (prolate) neutrino radiation is the most effective way of increasing the explosion energy among various types of explosions investigated in these studies. We discuss the reason for this. Our result is suggestive of the fact that the expanding materials of SN1987A is observed to have a prolate geometry.Comment: 15 pages, including 7 figures, to appear in PAS

Global Anisotropy Versus Small-Scale Fluctuations in Neutrino Flux in Core-Collapse Supernova Explosions

Effects of small-scale fluctuations in the neutrino radiation on core-collapse supernova explosions are examined. Through a parameter study with a fixed radiation field of neutrinos, we find substantial differences between the results of globally anisotropic neutrino radiation and those with fluctuations. As the number of modes of fluctuations increases, the shock positions, entropy distributions, and explosion energies approach those of spherical explosion. We conclude that global anisotropy of the neutrino radiation is the most effective mechanism of increasing the explosion energy when the total neutrino luminosity is given. This supports the previous statement on the explosion mechanism by Shimizu and coworkers.Comment: 14 pages, including 12 figures. To be published in the Astrophysical Journa

Stochastic Estimation of Nuclear Level Density in the Nuclear Shell Model: An Application to Parity-Dependent Level Density in 58^{58}Ni

We introduce a novel method to obtain level densities in large-scale shell-model calculations. Our method is a stochastic estimation of eigenvalue count based on a shifted Krylov-subspace method, which enables us to obtain level densities of huge Hamiltonian matrices. This framework leads to a successful description of both low-lying spectroscopy and the experimentally observed equilibration of $J^\pi=2^+$ and $2^-$ states in $^{58}$Ni in a unified manner.Comment: 13 pages, 4 figure

Core-Collapse Supernovae Induced by Anisotropic Neutrino Radiation

We demonstrate the important role of anisotropic neutrino radiation on the mechanism of core-collapse supernova explosions. Through a new parameter study with a fixed radiation field of neutrinos, we show that prolate explosions caused by globally anisotropic neutrino radiation is the most effective mechanism of increasing the explosion energy when the total neutrino luminosity is given. This is suggestive of the fact that the expanding materials of SN 1987A has a prolate geometry.Comment: in Proceedings of Int. conf. in hohour of the 60th birthday of Marcel Arnould, The Future Astronuclear Physics, From microscopic puzzles to macroscopic nightmares, Eds. H.M.J. Boffin et al., EAS Publication Series, EDP Sciences, in press (2004

Dynamical Modulation of Wintertime Synoptic-Scale Cyclone Activity over the Japan Sea due to Changbai Mountain in the Korean Peninsula

The dynamical impact of the Changbai Mountain Range in the Korean Peninsula on the extratropical cyclone activity over the Japan Sea in early winter is examined using the Weather Research Forecasting model. We have conducted two independent long-term integrations over 15 winter months (December only) from 2000 to 2014 with and without modified topography. The results show that the Changbai Mountain Range plays a vital role in increasing cyclone track frequency, low-level poleward eddy heat flux, and the local deepening rate over the Japan Sea through enhancement of the lower-tropospheric baroclinic zone (LTBZ). This mountain range gives rise to activation of the synoptic-scale cyclone activity over that region. From our case study on three typical cyclones, it is found that mesoscale structures in the vicinity of a cyclone’s center are dynamically modulated when it passes through the LTBZ and that cyclogenesis is triggered around that zone. A vorticity budget analysis shows that the stretching term relevant to enhanced low-level convergence plays a dominant role in intensifying cyclonic vorticities. We confirmed that the composite features of the three typical cases are consistent with the statistical ones of the dynamical modulation of the Changbai Mountain on synoptic-scale cyclone activity

Nanoscale Cu Wiring by Electrodeposition in Supercritical Carbon Dioxide Emulsified Electrolyte

Novel electrodeposition (ED) techniques utilizing supercritical carbon dioxide (scCO2) emulsions (SCE) are introduced. ScCO2 has low surface tension and high compatibility with hydrogen. Thus, this method is applied in fine Cu wiring to allow the complete filling of Cu into nanoscale confined space. The electrochemical reactions are carried out in emulsions composed of an aqueous electrolyte, scCO2, and surfactants. Three aspects in fine Cu wiring will be introduced, which are the dissolution of the Cu seed layer in the SCE, the gap-filling capability of the ED-SCE, and the contamination in the plated Cu. At first, the dissolution of the Cu seed layer in the SCE was observed. In order to prevent the dissolution of the Cu seed layer, the addition of Cu particles into the SCE was found to be effective. The electrolyte containing the SCE and the Cu particles is named scCO2 suspension (SCS). The gap-filling capability was evaluated using test element groups (TEGs) with patterns of vias with a diameter of 70 nm and an aspect ratio of 5. Many defects were observed in the vias filled using the conventional electrodeposition (CONV) method. On the other hand, defect-free fillings were obtained by the ED-SCS method. Because of the high-pressure environment needed to form the scCO2, the reaction cells are usually batch-type high-pressure vessels. In order to improve the feasibility of the ED-SCS technique, a continuous-flow reaction system is also proposed and examined using a round-type large-area TEG with a diameter of 300 mm. Complete fillings were obtained for vias with a diameter of 60 nm and an aspect ratio of 5 on the large-area TEG. This result was in good agreement with that of the batch-type reaction system and demonstrated the successful application of the continuous-flow system with ED-SCS