I=2I=2 ππ\pi\pi potential in the HAL QCD method with all-to-all propagators

In this paper, we perform the first application of the hybrid method (exact low modes plus stochastically estimated high modes) for all-to-all propagators to the HAL QCD method. We calculate the HAL QCD potentials in the $I=2$ $\pi\pi$ scattering in order to see how statistical fluctuations of the potential behave under the hybrid method. All of the calculations are performed with the 2+1 flavor gauge configurations on $16^3 \times 32$ lattice at the lattice spacing $a \approx 0.12$ fm and $m_{\pi} \approx 870$ MeV. It is revealed that statistical errors for the potential are enhanced by stochastic noises introduced by the hybrid method, which, however, are shown to be reduced by increasing the level of dilutions, in particular, that of space dilutions. From systematic studies, we obtain a guiding principle for a choice of dilution types/levels and a number of eigenvectors to reduce noise contaminations to the potential while keeping numerical costs reasonable. We also confirm that we can obtain the scattering phase shifts for the $I=2$ $\pi\pi$ system by the hybrid method within a reasonable numerical cost, which are consistent with the result obtained with the conventional method. The knowledge we obtain in this study will become useful to investigate hadron resonances which require quark annihilation diagrams such as the $\rho$ meson by the HAL QCD potential with the hybrid method.Comment: 20 pages, 10 figures, published version in PTE

I=2ππ potential in the HAL QCD method with all-to-all propagators

In this paper, we perform the first application of the hybrid method (exact low modes plus stochastically estimated high modes) for all-to-all propagators to the HAL QCD method. We calculate the HAL QCD potentials in the I=2ππ scattering in order to see how statistical fluctuations of the potential behave under the hybrid method. All of the calculations are performed with the 2+1 flavor gauge configurations on a 163×32 lattice at the lattice spacing a≈0.12 fm and mπ≈870 MeV. It is revealed that statistical errors for the potential are enhanced by stochastic noises introduced by the hybrid method, which, however, are shown to be reduced by increasing the level of dilutions, in particular, that of space dilutions. From systematic studies, we obtain a guiding principle for a choice of dilution types/levels and a number of eigenvectors to reduce noise contamination to the potential while keeping numerical costs reasonable. We also confirm that we can obtain the scattering phase shifts for the I=2ππ system by the hybrid method within a reasonable numerical cost; these phase shifts are consistent with the result obtained with the conventional method. The knowledge that we obtain in this study will become useful for the investigation of hadron resonances that require quark annihilation diagrams such as the ρ meson by the HAL QCD potential with the hybrid method

Author Correction: Fish proliferation and rare-earth deposition by topographically induced upwelling at the late Eocene cooling event (Scientific Reports, (2020), 10, 1, (9896), 10.1038/s41598-020-66835-8)

金沢大学理工研究域地球社会基盤学系An amendment to this paper has been published and can be accessed via a link at the top of the paper. © 2020, The Author(s)

Fish proliferation and rare-earth deposition by topographically induced upwelling at the late Eocene cooling event

金沢大学理工研究域地球社会基盤学系The deep-sea clay that covers wide areas of the pelagic ocean bottom provides key information about open-ocean environments but lacks age-diagnostic calcareous or siliceous microfossils. The marine osmium isotope record has varied in response to environmental changes and can therefore be a useful stratigraphic marker. In this study, we used osmium isotope ratios to determine the depositional ages of pelagic clays extraordinarily rich in fish debris. Much fish debris was deposited in the western North and central South Pacific sites roughly 34.4 million years ago, concurrent with a late Eocene event, a temporal expansion of Antarctic ice preceding the Eocene–Oligocene climate transition. The enhanced northward flow of bottom water formed around Antarctica probably caused upwelling of deep-ocean nutrients at topographic highs and stimulated biological productivity that resulted in the proliferation of fish in pelagic realms. The abundant fish debris is now a highly concentrated source of industrially critical rare-earth elements. © 2020, The Author(s)

The tremendous potential of deep-sea mud as a source of rare-earth elements

金沢大学理工研究域地球社会基盤学系Potential risks of supply shortages for critical metals including rare-earth elements and yttrium (REY) have spurred great interest in commercial mining of deep-sea mineral resources. Deep-sea mud containing over 5,000 ppm total REY content was discovered in the western North Pacific Ocean near Minamitorishima Island, Japan, in 2013. This REY-rich mud has great potential as a rare-earth metal resource because of the enormous amount available and its advantageous mineralogical features. Here, we estimated the resource amount in REY-rich mud with Geographical Information System software and established a mineral processing procedure to greatly enhance its economic value. The resource amount was estimated to be 1.2 Mt of rare-earth oxide for the most promising area (105 km2 × 0-10 mbsf), which accounts for 62, 47, 32, and 56 years of annual global demand for Y, Eu, Tb, and Dy, respectively. Moreover, using a hydrocyclone separator enabled us to recover selectively biogenic calcium phosphate grains, which have high REY content (up to 22,000 ppm) and constitute the coarser domain in the grain-size distribution. The enormous resource amount and the effectiveness of the mineral processing are strong indicators that this new REY resource could be exploited in the near future. © 2018 The Author(s)

Prediction of Acid Mine Drainage Treatment by Open Limestone-Alkaline Material Channel and Implications for the Large Scale Implementation of Passive Treatment

In decades, various studies on passive treatment methods of acid mine drainage (AMD) have been actively conducted in order to reduce the cost of AMD treatment. Open limestone channel is one of the most common methods and has already been implemented mainly in overseas. On the other hand, it is difficult to secure large channels in Japan due to its topography, we need to consider the use of alkaline materials with higher acid neutralization potential which enables successful treatment with narrower space. In this study, therefore, PAdeCS, a cement-derived environmental remediation agent, was used to remove the harmful metal elements by neutralization treatment. Then, we developed a simulation model assuming a combined system of open limestone channel and alkaline material (PAdeCS) channel and predicted the behavior of harmful metal elements within the combined channel. The simulation results showed that PAdeCS has extremely high acid neutralization potential, that high temperature is advantageous for neutralization treatment of harmful metal elements, and that the channel design needs to be changed depending on the initial drainage composition. Finally, a new flowchart for selecting the appropriate passive treatment method was proposed, which consists of three steps of the preferential removal of Fe, neutralization by limestone, and additional treatments

Partial wave decomposition on the lattice and its applications to the HAL QCD method

The approximated partial-wave decomposition method for discrete data on a cubic lattice, developed by Misner, is applied to the calculation of S-wave hadron-hadron scatterings by the HAL QCD method in lattice QCD. We consider the Nambu-Bethe-Salpeter (NBS) wave function for the spin-singlet ΛcN system calculated in (2+1)-flavor QCD on a (32a  fm)3 lattice with lattice spacing a≃0.0907  fm and mπ≃700  MeV. We find that by Misner's method the l=0 component can be successfully extracted from the NBS wave function projected to the A+1 representation of the cubic group, which contains small l≥4 components. Furthermore, while the higher partial-wave components are enhanced so as to produce significant comb-like structures in the conventional HAL QCD potential if the Laplacian approximated by the usual second-order difference is applied to the NBS wave function, such structures are found to be absent in the potential extracted by Misner's method, where the Laplacian can be evaluated analytically for each partial-wave component. Despite the difference in the potentials, the two methods give almost identical results on the central values and magnitude of statistical errors for the fits of the potentials, and consequently on the scattering phase shifts. This indicates not only that Misner's method works well in lattice QCD with the HAL QCD method, but also that the contaminations from higher partial waves in the study of S-wave scatterings are well under control even in the conventional HAL QCD method. It will be of interest to study interactions in higher partial-wave channels in the HAL QCD method with Misner's decomposition, where the utility of this new technique may become clearer

Derivation of Flotation Kinetic Model Combining Surface Property Analysis and Kinetics

Copper sulfide minerals are the major raw materials for copper products. Copper sulfide minerals are mined at copper mines and concentrated by flotation process. In recent years, the mining of refractory copper ores, which is difficult to concentrate by flotation due to their fine grain size, presence of multiple copper mineral species, and fluctuation of the content ratio of these minerals in feed ore. In addition, the hydrophilization of copper mineral surfaces due to oxidation and the mineral content variation of ore result in poor and unpredictable performance of flotation operation. In this study, therefore, we focused on the activation of the copper mineral surfaces using sodium hydrosulfide (NaHS) to render the surfaces hydrophobic and tried to quantify the effect of the fluctuation of mineral content ratio by using a new flotation kinetic model. Two samples showing different content ratios of chalcocite, bornite, and chalcopyrite and having fully oxidized surface were used in the flotation tests. We established a new flotation kinetic model by considering the reaction between the copper mineral surface and NaHS and the depression of floatability by adsorption of hydrogen sulfide ions onto the copper mineral surface. As a result, a good relation was confirmed between the model and the flotation test results for both ore samples. This result showed that our model can accurately predict the flotation results of refractory copper ores and will encourage the further usage of these refractory copper ores in the future