2021/04/22 更新

写真a

イエトミ ヒロシ
家富 洋
IYETOMI Hiroshi
所属
教育研究院 自然科学系 数理物質科学系列 教授
自然科学研究科 数理物質科学専攻 教授
理学部 理学科 教授
職名
教授
外部リンク

学位

  • 理学博士 ( 1984年3月   東京大学 )

研究キーワード

  • ネットワーク科学

  • 多変量解析

  • Computational Physics

  • Plasma

  • 計算物理

  • プラズマ

  • ナノマテリアル

  • 固体電解質

  • Nanomaterial

  • Solid Electrolyte

  • Glass

  • Econophysics

  • ガラス

  • 経済物理

研究分野

  • エネルギー / プラズマ科学

  • 情報通信 / ソフトコンピューティング

  • 情報通信 / 感性情報学

  • 情報通信 / 統計科学

  • 情報通信 / 感性情報学

  • 情報通信 / 統計科学

  • 自然科学一般 / 数理物理、物性基礎

  • エネルギー / プラズマ応用科学

  • 自然科学一般 / 数理物理、物性基礎

  • 情報通信 / ソフトコンピューティング

  • エネルギー / プラズマ応用科学

  • エネルギー / プラズマ科学

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経歴(researchmap)

  • 新潟大学   理学部   教授

    2013年5月 - 現在

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  • 東京大学   大学院経済学研究科   特任教授

    2012年4月 - 2013年4月

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  • Professor, Faculty of Science, Niigata University

    2002年 - 2012年3月

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  • 新潟大学   理学部   教授

    2002年 - 2012年3月

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  • Associate Professor, Faculty of Science, Niigata University

    1995年 - 2002年

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  • 新潟大学   理学部   助教授

    1995年 - 2002年

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  • Scientist, Energy Research Laboratory, Hitachi, Ltd.

    1993年 - 1994年

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  • (株)日立製作所   エネルギー研究所   研究員

    1993年 - 1994年

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  • アルゴンヌ国立研究所   物質科学部   研究員

    1987年9月 - 1989年8月

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  • 東京大学   理学部   助手

    1984年 - 1993年

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  • Assistant Professor, Faculty of Science, University of Tokyo,

    1984年 - 1993年

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経歴

  • 新潟大学   理学部 理学科   教授

    2017年4月 - 2021年3月

  • 新潟大学   自然科学研究科 数理物質科学専攻   教授

    2013年5月 - 2021年3月

  • 新潟大学   情報数理科学   教授

    2013年5月 - 2017年3月

  • 新潟大学   学術情報基盤機構 附属図書館   館長

    2010年11月 - 2012年3月

  • 新潟大学   物理学科   教授

    2002年2月 - 2012年3月

  • 新潟大学   理学部   助教授

    1995年1月 - 2002年1月

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学歴

  • 東京大学   大学院理学系研究科   物理学

    - 1984年3月

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    国名: 日本国

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  • 東京大学   理学部   物理学

    - 1979年3月

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    国名: 日本国

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所属学協会

 

論文

  • Relationship between Macroeconomic Indicators and Economic Cycles in U.S. (vol 10, 8420, 2020) 査読

    Hiroshi Iyetomi, Hideaki Aoyama, Yoshi Fujiwara, Wataru Souma, Irena Vodenska, Hiroshi Yoshikawa

    SCIENTIFIC REPORTS10 ( 1 )   2020年8月

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    記述言語:英語   出版者・発行元:NATURE PUBLISHING GROUP  

    DOI: 10.1038/s41598-020-70100-3

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  • Relationship between Macroeconomic Indicators and Economic Cycles in U.S 査読

    Hiroshi Iyetomi, Hideaki Aoyama, Yoshi Fujiwara, Wataru Souma, Irena Vodenska, Hiroshi Yoshikawa

    SCIENTIFIC REPORTS10 ( 1 )   2020年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:NATURE PUBLISHING GROUP  

    We analyze monthly time series of 57 US macroeconomic indicators (18 leading, 30 coincidental, and 9 lagging) and 5 other trade/money indexes. Using novel methods, we confirm statistically significant co-movements among these time series and identify noteworthy economic events. The methods we use are Complex Hilbert Principal Component Analysis (CHPCA) and Rotational Random Shuffling (RRS). We obtain significant complex correlations among the US economic indicators with leads/lags. We then use the Hodge decomposition to obtain the hierarchical order of each time series. The Hodge potential allows us to better understand the lead/lag relationships. Using both CHPCA and Hodge decomposition approaches, we obtain a new lead/lag order of the macroeconomic indicators and perform clustering analysis for positively serially correlated positive and negative changes of the analyzed indicators. We identify collective negative co-movements around the Dot.com bubble in 2001 as well as the Global Financial Crisis (GFC) in October 2008. We also identify important events such as the Hurricane Katrina in August 2005 and the Oil Price Crisis in July 2008. Additionally, we demonstrate that some coincidental and lagging indicators actually show leading indicator characteristics. This suggests that there is a room for existing indicators to be improved.

    DOI: 10.1038/s41598-020-65002-3

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  • Interindustry linkages of prices-Analysis of Japan's deflation 査読

    Yuichi Kichikawa, Hiroshi Iyetomi, Hideaki Aoyama, Yoshi Fujiwara, Hiroshi Yoshikawa

    PLOS ONE15 ( 2 )   2020年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PUBLIC LIBRARY SCIENCE  

    The interactions among macroprices with leads and lags play a significant role in explaining the behavior of an aggregate price index. Thus, to understand inflation and deflation, it is essential to explore the mechanism according to which these macroprices interact with each other. On the basis of a new method, we show that, irrespective of the sources of shocks, a robust flow of changes occurs in domestic prices from upstream to downstream. Moreover, we demonstrate that macroprices change in clusters, and we identify these clusters. Firms are not symmetric. Overall, our analysis suggests that the inertia arising from input/output linkages in production explains the behavior of aggregate prices.

    DOI: 10.1371/journal.pone.0228026

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  • Trade network reconstruction and simulation with changes in trade policy 査読

    Yuichi Ikeda, Hiroshi Iyetomi

    EVOLUTIONARY AND INSTITUTIONAL ECONOMICS REVIEW15 ( 2 ) 495 - 513   2018年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:SPRINGER HEIDELBERG  

    The interdependent nature of the global economy has become stronger with increases in international trade and investment. We propose a new model to reconstruct the international trade network and associated cost network by maximizing entropy based on local information about inward and outward trade. We show that the trade network can be successfully reconstructed using the proposed model. In addition to this reconstruction, we simulated structural changes in the international trade network caused by changing trade tariffs in the context of the government's trade policy. The simulation for the FOOD category shows that import of FOOD from the US to Japan increase drastically by halving the import cost. Meanwhile, the simulation for the MACHINERY category shows that exports from Japan to the US decrease drastically by doubling the export cost, while exports to the EU increased.

    DOI: 10.1007/s40844-018-0110-0

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  • Hierarchical communities in the walnut structure of the Japanese production network 査読

    Abhijit Chakraborty, Yuichi Kichikawa, Takashi Iino, Hiroshi Iyetomi, Hiroyasu Inoue, Yoshi Fujiwara, Hideaki Aoyama

    PLOS ONE13 ( 8 )   2018年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PUBLIC LIBRARY SCIENCE  

    This paper studies the structure of the Japanese production network, which includes one million firms and five million supplier-customer links. This study finds that this network forms a tightly-knit structure with a core giant strongly connected component (GSCC) surrounded by IN and OUT components constituting two half-shells of the GSCC, which we call awalnut structure because of its shape. The hierarchical structure of the communities is studied by the Infomap method, and most of the irreducible communities are found to be at the second level. The composition of some of the major communities, including overexpressions regarding their industrial or regional nature, and the connections that exist between the communities are studied in detail. The findings obtained here cause us to question the validity and accuracy of using the conventional input-output analysis, which is expected to be useful when firms in the same sectors are highly connected to each other.

    DOI: 10.1371/journal.pone.0202739

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  • Application of Complex Hilbert Principal Component Analysis to Financial Data 査読

    Wataru Souma, Hiroshi Iyetomi, Hiroshi Yoshikawa

    2017 IEEE 41ST ANNUAL COMPUTER SOFTWARE AND APPLICATIONS CONFERENCE (COMPSAC), VOL 2   391 - 394   2017年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    We addressed two areas of concern regarding the analysis of a financial time series with a correlation structure; coarse graining (or renormalization) and the extraction of leading and lagging structures. We introduce the complex Hilbert principal component analysis to solve these two problems, and apply them to the time series of 33 Tokyo Stock Exchange industry indices and Tokyo Stock Price Index. Our data analysis proved that the time difference between the leading indices and the lagging indices decreases when the market mode is dominant, i.e., the herd behavior of the market.

    DOI: 10.1109/COMPSAC.2017.63

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  • Backbone of credit relationships in the Japanese credit market 査読

    Luca Marotta, Salvatore Micciche, Yoshi Fujiwara, Hiroshi Iyetomi, Hideaki Aoyama, Mauro Gallegati, Rosario N. Mantegna

    EPJ DATA SCIENCE5   2016年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:SPRINGEROPEN  

    We detect the backbone of the weighted bipartite network of the Japanese credit market relationships. The backbone is detected by adapting a general method used in the investigation of weighted networks. With this approach we detect a backbone that is statistically validated against a null hypothesis of uniform diversification of loans for banks and firms. Our investigation is done year by year and it covers more than thirty years during the period from 1980 to 2011. We relate some of our findings with economic events that have characterized the Japanese credit market during the last years. The study of the time evolution of the backbone allows us to detect changes occurred in network size, fraction of credit explained, and attributes characterizing the banks and the firms present in the backbone.

    DOI: 10.1140/epjds/s13688-016-0071-7

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  • Interdependencies and Causalities in Coupled Financial Networks 査読

    Irena Vodenska, Hideaki Aoyama, Yoshi Fujiwara, Hiroshi Iyetomi, Yuta Arai

    PLOS ONE11 ( 3 )   2016年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PUBLIC LIBRARY SCIENCE  

    We explore the foreign exchange and stock market networks for 48 countries from 1999 to 2012 and propose a model, based on complex Hilbert principal component analysis, for extracting significant lead-lag relationships between these markets. The global set of countries, including large and small countries in Europe, the Americas, Asia, and the Middle East, is contrasted with the limited scopes of targets, e.g., G5, G7 or the emerging Asian countries, adopted by previous works. We construct a coupled synchronization network, perform community analysis, and identify formation of four distinct network communities that are relatively stable over time. In addition to investigating the entire period, we divide the time period into into "mild crisis," (1999-2002), "calm," (2003-2006) and "severe crisis" (2007-2012) sub-periods and find that the severe crisis period behavior dominates the dynamics in the foreign exchange-equity synchronization network. We observe that in general the foreign exchange market has predictive power for the global stock market performances. In addition, the United States, German and Mexican markets have forecasting power for the performances of other global equity markets.

    DOI: 10.1371/journal.pone.0150994

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  • Dynamics of Commodity Price Fluctuations in Japan 査読

    Yoshi Fujiwara, Hideaki Aoyama, Hiroshi Iyetomi, Hiroshi Yoshikawa

    PROCEEDINGS OF ECCS 2014: EUROPEAN CONFERENCE ON COMPLEX SYSTEMS   297 - 308   2016年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:SPRINGER  

    Deflation is a most important economic problem having been faced by Japan, and also developed countries in Europe, under zero interest rate. How individual prices influence each other, namely the dynamics of a large number of commodity prices and fluctuations plays a crucial role there. By using hundreds of individual commodities and their prices that comprise the import price, corporate goods price and consumer price indices, we show that price fluctuations have frequencies and synchronizations specific to space and time. Space means industrial sectors for the commodities and how they are located in the supplier-customer network. Temporal structure includes background movement due to deflation, inflation and exogenous shocks such as VAT (consumption tax) rate changes, the Lehman shock and so forth, but also endogenous shocks or mutual influences among the commodities.

    DOI: 10.1007/978-3-319-29228-1_25

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  • Bank-Firm Credit Network in Japan: An Analysis of a Bipartite Network 査読

    Luca Marotta, Salvatore Micciche, Yoshi Fujiwara, Hiroshi Iyetomi, Hideaki Aoyama, Mauro Gallegati, Rosario N. Mantegna

    PLOS ONE10 ( 5 )   2015年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PUBLIC LIBRARY SCIENCE  

    We investigate the networked nature of the Japanese credit market. Our investigation is performed with tools of network science. In our investigation we perform community detection with an algorithm which is identifying communities composed of both banks and firms. We show that the communities obtained by directly working on the bipartite network carry information about the networked nature of the Japanese credit market. Our analysis is performed for each calendar year during the time period from 1980 to 2011. To investigate the time evolution of the networked structure of the credit market we introduce a new statistical method to track the time evolution of detected communities. We then characterize the time evolution of communities by detecting for each time evolving set of communities the overexpression of attributes of firms and banks. Specifically, we consider as attributes the economic sector and the geographical location of firms and the type of banks. In our 32-year-long analysis we detect a persistence of the over-expression of attributes of communities of banks and firms together with a slow dynamic of changes from some specific attributes to new ones. Our empirical observations show that the credit market in Japan is a networked market where the type of banks, geographical location of firms and banks, and economic sector of the firm play a role in shaping the credit relationships between banks and firms.

    DOI: 10.1371/journal.pone.0123079

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  • Equilibrium distribution of labor productivity: a theoretical model 査読

    Hideaki Aoyama, Hiroshi Iyetomi, Hiroshi Yoshikawa

    JOURNAL OF ECONOMIC INTERACTION AND COORDINATION10 ( 1 ) 57 - 66   2015年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:SPRINGER HEIDELBERG  

    We construct a theoretical model for equilibrium distribution of workers across sectors with different labor productivity, assuming that a sector can accommodate a limited number of workers which depends only on its productivity. A general formula for such distribution of productivity is obtained, using the detail-balance condition necessary for equilibrium in the Ehrenfest-Brillouin model. We also carry out an empirical analysis on the average number of workers in given productivity sectors on the basis of an exhaustive dataset in Japan. The theoretical formula succeeds in explaining the two distinctive observational facts in a unified way, that is, a Boltzmann distribution with negative temperature on low-to-medium productivity side and a decreasing part in a power-law form on high productivity side.

    DOI: 10.1007/s11403-013-0118-9

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  • Complex principle component analysis on dynamic correlation structure in price index data 査読

    Yuichi Kichikawa, Yuta Arai, Hiroshi Iyetomi

    KNOWLEDGE-BASED AND INTELLIGENT INFORMATION & ENGINEERING SYSTEMS 19TH ANNUAL CONFERENCE, KES-201560   1836 - 1845   2015年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:ELSEVIER SCIENCE BV  

    We carry out multivariate time series analysis on price indices of individual goods and services collected over the last 35 years in Japan. Adoption of the complex principal component analysis (CPCA) enables us to have a new insight into dynamic correlation structure involved in the price data. The CPCA is based on complexification of real data using the Hilbert transformation; lead-lag relations between individual prices manifest in a form of instantaneous phases of the complex time series. The correlation matrix in the CPCA is purified by adopting the random matrix theory as a null hypothesis for removal of statistical noises. We identify four significant eigenmodes for price movement which are free from seasonal variations. Each of them has different characteristics of dynamical correlations and is shown to be responsive to different economic events. (C) 2015 The Authors. Published by Elsevier B.V.

    DOI: 10.1016/j.procs.2015.08.294

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  • Dynamic Stock Correlation Network 査読

    Yuta Arai, Takeo Yoshikawa, Hiroshi Iyetomi

    KNOWLEDGE-BASED AND INTELLIGENT INFORMATION & ENGINEERING SYSTEMS 19TH ANNUAL CONFERENCE, KES-201560   1826 - 1835   2015年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:ELSEVIER SCIENCE BV  

    Financial markets are the outcome of highly complex interactions among a number of agents. Such a complex system possibly contains all sorts of features, e.g., not only static but also dynamic. Here we study dynamic correlations hidden in the S&P 500 market by adopting a combined method of the Complex Principal Component Analysis (CPCA) and the Random Matrix Theory (RMT). The CPCA is entirely dependent on complexification of time series using the Hilbert transformation and enables us to extract correlations between stock prices moving with different phases to one another. The RMT serves as a null hypothesis for distinguishing true correlations from noisy financial data. The extracted information on dynamic correlations of the market is projected onto a correlation network in which pairs of stocks with phase difference smaller than certain threshold are linked with strength of their correlations as weight. We then detect communities of comoving stocks in the network and also elucidate lead-lag relationship between those communities. (C) 2015 The Authors. Published by Elsevier B.V.

    DOI: 10.1016/j.procs.2015.08.293

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  • Complex Principal Component Analysis of Dynamic Correlations in Financial Markets 査読

    Yuta Arai, Takeo Yoshikawa, Hiroshi Iyetomi

    INTELLIGENT DECISION TECHNOLOGIES255   111 - 119   2013年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IOS PRESS  

    Integration of principal component analysis (PCA) with random matrix theory (RMT) has been successful in analyzing cross correlations between stock price movements in financial markets. RMT is used as a null hypothesis to distinguish between genuine cross correlations and noises. In this paper, we develop a RMT-aided complex PCA method based on the Hilbert transformation of time series. The complex data thus generated carry dynamic information in a form of instantaneous phase; the conventional PCA is entirely dependent on simultaneous correlations in time. Accordingly RMT is generalized to be adaptable to complex PCA. The data set analyzed here is daily returns in Tokyo Stock Exchange (TSE) spanning from 1996 to 2006. Diagonalization of the complex correlation matrix enables us to find that a small number of the eigenvalues certainly deviate from the RMT prediction. The largest eigenvalue represents a market mode in which all of the stock prices move in a collective way. The eigenvectors of the other remaining large eigenvalues clearly show formation of stock groups as characterized by business sectors and also indicates existence of dynamical correlations between some sectors.

    DOI: 10.3233/978-1-61499-264-6-111

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  • Comparative Study of Correlations in Financial Markets 査読

    Takeo Yoshikawa, Yuta Arai, Hiroshi Iyetomi

    INTELLIGENT DECISION TECHNOLOGIES255   104 - 110   2013年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IOS PRESS  

    We elucidate correlations among stock price movements in S&P 500 and Tokyo Stock Exchange (TSE) taking advantage of the concept of community in networks. The correlation matrix, purified by random matrix theory, is regarded as the adjacency matrix for a stock correlation network. The network thus constructed has links with weights of either sign depending on whether stocks are correlated (positive) or anticorrelated (negative). Community is defined here as a group of stocks related to each other with positive correlation coefficients. The community detection allows us to find that the stocks in S&P 500 are split up into four communities with two conflicting triangular relations. In TSE, there exists three communities of stocks forming a conflicting triangle. We thus see that the frustrated correlation structure is common to the well-developed financial markets.

    DOI: 10.3233/978-1-61499-264-6-104

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  • Temporal Change of Community Structure in the Japanese Credit Network 査読

    Yuki Matsuura, Takashi Iino, Hiroshi Iyetomi

    INTELLIGENT DECISION TECHNOLOGIES255   399 - 408   2013年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IOS PRESS  

    Possibility of risk contagion over an entire financial system may be elucidated by studying relationship among creditors and borrowers. Here we study temporal change of community structure of a credit network formed by banks and listed firms through their financial relations over the last 30 years in Japan; the communities may be regarded as reflecting concentration of risk. The network is a bipartite graph consisting of two species of nodes connected with bidirectional links. The direction of links is identified with that of risk flows and their weights are relative loans with respect to the targets. In a partial credit network obtained only with the links pointing from firms toward banks, the city banks forms one major community in most of the time period to share risk when firms go wrong. On the other hand, a partial network only with the links from banks toward firms is decomposed into communities of similar size each of which has its own city bank. Finally we take overlapping parts of the two community sets to find cores of the risk concentration in the credit network.

    DOI: 10.3233/978-1-61499-264-6-399

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  • ECONOPHYSICS 2011 - THE HITCHHIKER'S GUIDE TO THE ECONOMY Preface 査読

    Hideaki Aoyama, Yoshi Fujiwara, Hiroshi Iyetomi, Aki-Hiro Sato

    PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT ( 194 ) I - II   2012年

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    記述言語:英語   出版者・発行元:PROGRESS THEORETICAL PHYSICS PUBLICATION OFFICE  

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  • Modeling of Climate Data in Terms of AR(1) Process Contaminated with Noise 査読

    Yuta Arai, Hiroshi Iyetomi

    INTELLIGENT DECISION TECHNOLOGIES (IDT'2012), VOL 216   415 - 422   2012年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:SPRINGER-VERLAG BERLIN  

    It is widely recognized that teleconnections (correlations between climates at remote places) such as El Nino play a crucial role in understanding abnormal weather phenomena. To extract such correlations in multivariate climate data, the random matrix theory (RMT) combined with the principal component analysis (PCA) can be successfully used; the RMT has power to distinguish between statistically meaningful correlations and noises. Here we demonstrate that sea level pressure (SLP), which is one of basic meteorological measurements for teleconnections, have characteristic autocorrelations. Unfortunately the standard RMT is not able to distinguish between autocorrelations and cross-correlations. We show that an AR(1) process contaminated with noise reproduces the autocorrelations of the SLP quite well. Then we estimate autocorrelation effects on the eigenvalue distribution of the SLP correlation matrix, which makes the extraction procedure of genuine cross-correlations more reliable.

    DOI: 10.1007/978-3-642-29920-9_42

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  • Directional Bias between Communities of a Production Network in Japan 査読

    Takashi Iino, Hiroshi Iyetomi

    INTELLIGENT DECISION TECHNOLOGIES (IDT'2012), VOL 216   273 - 280   2012年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:SPRINGER-VERLAG BERLIN  

    We investigate a production network constructed by about 800 thousand firms in Japan with focus on its transaction flow between communities. Communities detected by maximizing modularity often contain nodes with common properties such as characterized by regions or industry sectors. Communities may thus upstream-downstream relationship according to their characteristics. Such directional bias of the connections between communities is evaluated through a polarization matrix of the network direction. We also devise a visualization method for directed network based on physical model. We attempt to draw a map of Japanese transaction flow in viewpoint of community structure.

    DOI: 10.1007/978-3-642-29920-9_28

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  • Detection of Comoving Groups in a Financial Market 査読

    Takeo Yoshikawa, Takashi Iino, Hiroshi Iyetomi

    INTELLIGENT DECISION TECHNOLOGIES (IDT'2012), VOL 115   481 - 486   2012年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:SPRINGER-VERLAG BERLIN  

    We reported a correlation structure hidden in the Tokyo Stock Exchange (TSE) market at KES-IDT2011. By regarding the TSE market as a network (stocks and correlation coefficients correspond to nodes and weights of links between nodes, respectively) and minimizing the Frustration among nodes, the stocks were decomposed into four comoving groups forming communities. Three of them are strongly anticorrelated to each other, and the remainder is comparatively neutral to the rest of the communities. In this paper we further extend the previous work to detect tightly-coupled groups within the communities; "Hamiltonian" is used instead of the Frustration. The Hamiltonian has two parameters which control degree of strength for correlations to be extracted. It is found that six sectors (Electric Appliance, Banks, Electric Power & Supply, Information & Communication, Securities & Commodity Futures, and Insurance) form strong cores in the communities.

    DOI: 10.1007/978-3-642-29977-3_48

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  • Labor Productivity Distribution with Negative Temperature 査読

    Hiroshi Iyetomi

    PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT ( 194 ) 135 - 143   2012年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PROGRESS THEORETICAL PHYSICS PUBLICATION OFFICE  

    Exhaustive financial data of firms in Japan enables us to shed light on how the labor productivity, defined here as value added produced by one worker in a year, is diverse across firms and workers. Statistical equilibrium theory reinforced with the concept of negative temperature turns out to be useful to explain the empirical facts on a major part of the distribution of workers over labor productivity states, where particle and single-particle energy are replaced by worker and labor productivity, respectively. The zero-temperature state in the negative temperature regime corresponds to the optimized state for the current mainstream economics, where all workers are allocated to a state of the highest productivity. Significant difference in temperature is observed between the manufacturing and nonmanufacturing sectors. The negative temperature in the nonmanufacturing sector is three times lower than that in the manufacturing sector, indicating that the former may suffer from a much wider demand gap. In contrast, the two sectors are almost in equilibrium with respect to exchange of workers.

    DOI: 10.1143/PTPS.194.135

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  • Numerical Study of Generalized Random Correlation Matrices: Autocorrelation Effects 査読

    Yuta Arai, Hiroshi Iyetomi

    PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT ( 194 ) 84 - 93   2012年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PROGRESS THEORETICAL PHYSICS PUBLICATION OFFICE  

    We report the numerical calculations of the maximal eigenvalue for random correlation matrices which contain autocorrelations in data. Here the AR(1) model is adopted for such a study, we work out an empirical formula for autocorrelation correction of the maximal eigenvalue, which are accurate in a wide range of parameters. As an application of this formula, we propose a criterion to single out statistically meaningful correlations in the principal component analysis. The new criterion within the AR(1) model incorporates autocorrelation effects into the current method based on the random matrix theory.

    DOI: 10.1143/PTPS.194.84

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  • Observation of Frustrated Correlation Structure in a Well-Developed Financial Market 査読

    Takeo Yoshikawa, Takashi Iino, Hiroshi Iyetomi

    PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT ( 194 ) 55 - 63   2012年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PROGRESS THEORETICAL PHYSICS PUBLICATION OFFICE  

    We approach the correlation structure in the Tokyo Stock Exchange (TSE) market through a concept of community of network. To construct a network, the correlation matrix of stock price changes, purified by random matrix theory, is regarded as an adjacency matrix. The stock correlation network thus constructed has negatively weighted links as well as positively weighted links. By extracting groups in which stocks are mainly interconnected by positive links, we find that the stocks decomposed into four comoving groups forming communities, three of which are strongly anticorrelated to each other, and the remainder is comparatively neutral to the rest of the communities. The conflicting triangle relationship between communities may cause complicated behavior in a well-development market such as TSE. Additionally, it is observed that some industrial sectors form distinctive coherent groups and others are separated to competing communities.

    DOI: 10.1143/PTPS.194.55

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  • Coupled Oscillator Model of the Business Cycle with Fluctuating Goods Markets 査読

    Yuichi Ikeda, Hideaki Aoyama, Yoshi Fujiwara, Hiroshi Iyetomi, Kazuhiko Ogimoto, Wataru Souma, Hiroshi Yoshikawa

    PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT ( 194 ) 111 - 121   2012年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PROGRESS THEORETICAL PHYSICS PUBLICATION OFFICE  

    The sectoral synchronization observed for the Japanese business cycle in the Indices of Industrial Production data is an example of synchronization. The stability of this synchronization under a shock, e.g., fluctuation of supply or demand, is a matter of interest in physics and economics. We consider an economic system made up of industry sectors and goods markets in order to analyze the sectoral synchronization observed for the Japanese business cycle. A coupled oscillator model that exhibits synchronization is developed based on the Kuramoto model with inertia by adding goods markets, and analytic solutions of the stationary state and the coupling strength are obtained. We simulate the effects on synchronization of a sectoral shock for systems with different price elasticities and the coupling strengths. Synchronization is reproduced as an equilibrium solution in a nearest neighbor graph. Analysis of the order parameters shows that the synchronization is stable for a finite elasticity, whereas the synchronization is broken and the oscillators behave like a giant oscillator with a certain frequency additional to the common frequency for zero elasticity.

    DOI: 10.1143/PTPS.194.111

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  • Subcommunities and Their Mutual Relationships in a Transaction Network 査読

    Takashi Iino, Hiroshi Iyetomi

    PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT ( 194 ) 144 - 157   2012年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PROGRESS THEORETICAL PHYSICS PUBLICATION OFFICE  

    We investigate a Japanese transaction network consisting of about 800 thousand firms (nodes) and four million business relations (links) with focus on its modular structure. Communities detected by maximizing modularity often are dominated by firms with common features or behaviors in the network, such as characterized by regions or industry sectors. However, it is well known that the modularity optimization approach has a resolution limit problem, that is, it fails in identifying fine communities buried in large communities. To unfold such hidden structures, we apply the community detection to each of subnetworks formed by isolating those communities from the whole body. Subcommunities thus identified are composed of firms with finer regions, more specified sectors or business affiliations. Also we introduce a new idea of reduced modularity matrix to measure the strength of relations between (sub)communities.

    DOI: 10.1143/PTPS.194.144

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  • A paradigm shift from production function to production copula: statistical description of production activity of firms 査読

    Hiroshi Iyetomi, Hideaki Aoyama, Yoshi Fujiwara, Yuichi Ikeda, Wataru Souma

    QUANTITATIVE FINANCE12 ( 9 ) 1453 - 1466   2012年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ROUTLEDGE JOURNALS, TAYLOR & FRANCIS LTD  

    The heterogeneity of economic agents is emphasized in a new trend in macroeconomics. Accordingly, the new emerging discipline requires one to replace the production function, one of the key ideas in conventional economics, by an alternative that can take explicit account of the distribution of firms' production activities. In this paper we propose a new idea referred to as a production copula; a copula is an analytic means for modeling the dependence among variables. Such a production copula predicts the value added by firms with given capital and labor in a probabilistic way. It is thereby in sharp contrast to the production function, where the output of firms is completely deterministic. We demonstrate the empirical construction of a production copula using financial data of listed Japanese firms. Analysis of the data shows that there are significant correlations among capital, labor and value added, and confirms that the values added are too widely scattered to be represented by a production function. We employ four models for the production copula, that is trivariate versions of Frank, Gumbel and survival Clayton and non-exchangeable trivariate Gumbel. The latter was found to be the best.

    DOI: 10.1080/14697688.2010.548823

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  • An ab initio analysis of electronic states associated with a silicon vacancy in cubic symmetry 査読

    T. Ogawa, K. Tsuruta, H. Iyetomi

    Solid State Communications151 ( 21 ) 1605 - 1608   2011年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The electronic orbitals localized in the vicinity of a vacancy in a silicon crystal are calculated by an ab initio method based on the density functional theory and analyzed in association with the elastic softening observed by the recent ultrasonic experiments, especially focused on an estimate of the electric quadrupole moments. The localized orbitals due to the existence of a vacancy show largely extended properties and the quadrupole moments calculated from the orbitals indicate the strong dependence on cell sizes up to 511 atoms in the basic cell. Asymptotic values of the quadrupole moments in the limit of large size are obtained by an extrapolating method. It is shown that the quadrupole moments are enhanced due to the extension of the orbitals and the ratio of the quadrupole moments of Γ5 and Γ3 symmetries agrees well with the value deduced from the experimental results. © 2011 Elsevier Inc. All rights reserved.

    DOI: 10.1016/j.ssc.2011.07.020

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  • What causes business cycles? Analysis of the Japanese industrial production data 査読

    Hiroshi Iyetomi, Yasuhiro Nakayama, Hiroshi Yoshikawa, Hideaki Aoyama, Yoshi Fujiwara, Yuichi Ikeda, Wataru Souma

    JOURNAL OF THE JAPANESE AND INTERNATIONAL ECONOMIES25 ( 3 ) 246 - 272   2011年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ACADEMIC PRESS INC ELSEVIER SCIENCE  

    Iyetomi, Hiroshi-What causes business cycles? Analysis of the Received 29 January 2010 Japanese industrial production dataWe explore what causes business cycles by analyzing the Japanese industrial production data. The methods used are spectral analysis and factor analysis. Using the random matrix theory, we show that two largest eigenvalues are significant. Taking advantage of the information revealed by disaggregated data, we identify the first dominant factor as the aggregate demand, and the second factor as inventory adjustment. They cannot be reasonably interpreted as technological shocks. We also demonstrate that in terms of two dominant factors, shipments lead production by four months. Furthermore, out-of-sample test demonstrates that the model holds up even under the 2008-2009 recession. Because a fall of output during 2008-2009 was caused by an exogenous drop in exports, it provides another justification for identifying the first dominant factor as the aggregate demand. All the findings suggest that the major cause of business cycles is real demand shocks.. Japanese Int. Economies xxx (xx) (2011) xxx-xxx. Department of Physics, Niigata University, Niigata 950-2181, Japan; Faculty of Economics, University of Tokyo, Tokyo 113-0033, Japan; Department of Physics, Kyoto University, Kyoto 606-8501, Japan; Graduate School of Simulation Studies, University of Hyogo, Kobe 6500047, Japan; Institute of Industrial Science, University of Tokyo, Tokyo 153-8505, Japan; College of Science and Technology, Nihon University, Chiba 274-8501, Japan. (C) 2011 Elsevier Inc. All rights reserved.

    DOI: 10.1016/j.jjie.2011.06.002

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  • Fluctuation-dissipation theory of input-output interindustrial relations 査読

    Hiroshi Iyetomi, Yasuhiro Nakayama, Hideaki Aoyama, Yoshi Fujiwara, Yuichi Ikeda, Wataru Souma

    PHYSICAL REVIEW E83 ( 1 )   2011年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER PHYSICAL SOC  

    In this study, the fluctuation-dissipation theory is invoked to shed light on input-output interindustrial relations at a macroscopic level by its application to indices of industrial production (IIP) data for Japan. Statistical noise arising from finiteness of the time series data is carefully removed by making use of the random matrix theory in an eigenvalue analysis of the correlation matrix; as a result, two dominant eigenmodes are detected. Our previous study successfully used these two modes to demonstrate the existence of intrinsic business cycles. Here a correlation matrix constructed from the two modes describes genuine interindustrial correlations in a statistically meaningful way. Furthermore, it enables us to quantitatively discuss the relationship between shipments of final demand goods and production of intermediate goods in a linear response framework. We also investigate distinctive external stimuli for the Japanese economy exerted by the current global economic crisis. These stimuli are derived from residuals of moving-average fluctuations of the IIP remaining after subtracting the long-period components arising from inherent business cycles. The observation reveals that the fluctuation-dissipation theory is applicable to an economic system that is supposed to be far from physical equilibrium.

    DOI: 10.1103/PhysRevE.83.016103

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  • Multiscale community analysis of a production network of firms in Japan 査読

    Takashi Iino, Hiroshi Iyetomi

    Smart Innovation, Systems and Technologies10   537 - 545   2011年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

    We investigate a production network constructed by about 800 thousand firms in Japan through four million transaction relations with focus on its community structure. Communities detected by maximizing modularity often contain nodes with common properties such as characterized by regions or industry sectors. However, the modularity optimization approach suffers from the resolution limit problem
    small but important communities tend to be combined into a single large group. To unfold such hidden structure, the community detection was reiterated within each of major communities. Then it was found that the communities were composed of well-defined subcommunities, some of which were separated into smaller groups with more specified regions or industry sectors. Furthermore, a new tool is proposed for measuring the strength of relations between those subcommunities. It is shown to be useful to elucidate the multiscale structure of the network. © 2011 Springer-Verlag Berlin Heidelberg.

    DOI: 10.1007/978-3-642-22194-1_53

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  • Market structure as a network with positively and negatively weighted links 査読

    Takeo Yoshikawa, Takashi Iino, Hiroshi Iyetomi

    Smart Innovation, Systems and Technologies10   511 - 518   2011年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

    Correlation structure in the Tokyo Stock Exchange market is studied from a network viewpoint. The correlation matrix of stock price changes, purified by random matrix theory, is regarded as an adjacency matrix for a network. The stock network thus constructed has weighted links and furthermore those weights can be even negative. By minimizing of the frustration among nodes, it is found that the stocks are decomposed into four comoving groups forming communities, three of which are strongly anticorrelated to each other. Such a frustrated triangle relationship among the groups may give rise to complicated market behavior. © 2011 Springer-Verlag Berlin Heidelberg.

    DOI: 10.1007/978-3-642-22194-1_50

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  • Numerical study of random correlation matrices: Finite-size effects 査読

    Yuta Arai, Kouichi Okunishi, Hiroshi Iyetomi

    Smart Innovation, Systems and Technologies10   557 - 565   2011年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

    We report the numerical calculations of the distribution of maximal eigenvalue for various size of random correlation matrices. Such an extensive study enables us to work out empirical formulas for the average and standard deviation of the maximal eigenvalue, which are accurate in a wide range of parameters. As an application of those formulas, we propose a criterion to single out statistically meaningful correlations in the principal component analysis. The new criterion incorporates finite-size effects into the current method based on the random matrix theory, which gives the exact results in the infinite-size limit. © 2011 Springer-Verlag Berlin Heidelberg.

    DOI: 10.1007/978-3-642-22194-1_55

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  • Analysis of labor productivity using large-scale data of firm′s financial statements 査読

    Y. Ikeda, W. Souma, H. Aoyama, Y. Fujiwara, H. Iyetomi

    European Physical Journal B76 ( 4 ) 491 - 499   2010年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We investigated labor productivity distribution by analyzing large-scale financial statement data consisting of listed and unlisted Japanese firms to clarify the characteristics of the Japanese labor market. Both high and low productivity sides of the labor productivity distribution follows the power-law distribution. Large inequality in the low productivity side was observed only for the manufacturing sectors in Japan fiscal year (JFY) 1999 and observed for both the manufacturing and non-manufacturing sectors in JFY 2002. The decline in the Japanese GDP in JFY 1999 and JFY 2002 were coincided with the large inequality in the low productivity side of the distribution. A lower peak was found for all non-manufacturing sectors. This might be the origin of the low productivity of the non-manufacturing sectors reported in recent economic studies. © 2009 EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg.

    DOI: 10.1140/epjb/e2009-00421-y

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  • Productivity dispersion: facts, theory, and implications 査読

    Hideaki Aoyama, Hiroshi Yoshikawa, Hiroshi Iyetomi, Yoshi Fujiwara

    JOURNAL OF ECONOMIC INTERACTION AND COORDINATION5 ( 1 ) 27 - 54   2010年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:SPRINGER HEIDELBERG  

    This paper discusses the stylized facts, the theory, and the remaining problems of productivity dispersion, which is essentially related to the concept of equilibrium in the neoclassical theory. Empirical study of data relating to Japanese firms shows that they all obey the Pareto law, and also that the Pareto index decreases with the level of aggregation. In order to explain these two stylized facts we propose a theoretical framework built on the basic principle of statistical physics and on the concept of superstatistics, an approach that accommodates fluctuations of aggregate demand. We show that the allocation of production factors depends crucially on the level of aggregate demand, and that the higher the level of aggregate demand, the closer the economy is to the frontier of the production possibility set.

    DOI: 10.1007/s11403-010-0063-9

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  • Structure analyses of a large-scale transaction network through visualization based on molecular dynamics 査読

    K. Kamehama, T. Iino, H. Iyetomi, Y. Ikeda, T. Ohnishi, H. Takayasu, M. Takayasu

    Journal of Physics: Conference Series221   2010年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:Institute of Physics Publishing  

    We shed light on industrial structure of the economic system in Japan by combining visualization technique and community analysis in this and an accompanying paper. Here we focus on visualization of a production network comprising submillion nodes (firms) and three million links (transaction relations). A network structure is optimized through molecular dynamics simulation with a spring-electrical model in a three-dimensional space. The lowest-energy state in the model, corresponding to a crystalline state in a physical system, is expected to give a comprehensible view on the network. Then we discuss how firms are distributed in the optimized network structure by classifying them according to sectors, sizes or regions. The distributions of firms reflect characteristics of individual classifications. Also propagation of the shock due to a recent economic scandal over the network is visualized. © 2010 IOP Publishing Ltd.

    DOI: 10.1088/1742-6596/221/1/012013

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  • Molecular-dynamics simulation of the quasi liquid layer of ice lh 査読

    Mizuki Kuga, Takafumi Ogawa, Hiroshi Iyetomi

    Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research2010   182   2010年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.14851/jcsir.2010.0.182.0

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  • Density-Functional Analysis on Vacancy Orbital and its Elastic Response of Silicon 査読

    Takafumi Ogawa, Kenji Tsuruta, Hiroshi Iyetomi, Hiroshi Y. Kaneta, Terutaka Goto

    RELIABILITY AND MATERIALS ISSUES OF SEMICONDUCTOR OPTICAL AND ELECTRICAL DEVICES AND MATERIALS1195   2010年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:MATERIALS RESEARCH SOC  

    Recent experiments on ultrasonic measurements of non-doped and boron-doped silicon indicate that vacancies in crystalline silicon can be detected through the elastic softening at low temperature. This is attributed to enhanced response of electronic quadrupole localized at the vacancies to the elastic strain. In the present work, the electronic quadrupole moment of the vacancy orbital in silicon and their strain susceptibility are evaluated quantitatively by using the density-functional method. We show the orbital of gap state is localized around vacancy but extended over several neighbors. The effect of applied magnetic field on the vacancy orbital and its multipole structures are also investigated. We find that the results obtained from these calculations are consistent with the ultrasonic experiments.

    DOI: 10.1557/PROC-1195-B08-11

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  • Community structure in a large-scale transaction network and visualization 査読

    T. Iino, K. Kamehama, H. Iyetomi, Y. Ikeda, T. Ohnishi, H. Takayasu, M. Takayasu

    Journal of Physics: Conference Series221   2010年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:Institute of Physics Publishing  

    We analyze a transaction network of about 800 thousand Japanese firms to elucidate its community structure. Finding community in networks means the appearance of dense connected groups of vertices and sparse connections between groups. We adopt modularity as a quality function of communities introduced by Newman. The modularity optimization is one of effective approaches to find community. We first use a bottom-up algorithm, which makes the optimization fast by using a greedy algorithm. For the community extraction, the greedy algorithm is widely used, however, may not sufficiently optimize modularity because the optimization tends to be trapped by a local maximum especially for large-scale networks. Alternatively we propose a top-down algorithm with implementation of an annealing method and compare effectiveness of the two algorithms. We also compare the results of the community analysis with images of network structure visualized by molecular dynamics method. The vertices belonging to the same community are spatially located close to each other. The community structure determined by the modularity optimization is well reproduced in the network structure obtained by molecular dynamics. © 2010 IOP Publishing Ltd.

    DOI: 10.1088/1742-6596/221/1/012012

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  • Superstatistics of Labour Productivity in Manufacturing and Nonmanufacturing Sectors 査読

    Hideaki Aoyama, Yoshi Fujiwara, Yuichi Ikeda, Hiroshi Iyetomi, Wataru Souma

    ECONOMICS-THE OPEN ACCESS OPEN-ASSESSMENT E-JOURNAL3   2009年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:KIEL INST WORLD ECONOMY  

    Labour productivity distribution (dispersion) is studied within the framework of statistical physics and the result is compared with the outcome of the empirical analysis. Superstatistics is presented as a natural theoretical framework for the productivity distribution. The demand index. is proposed within this framework as a new business index. Productivity analysis is made on the Japanese data covering small-to-medium to large firms from 1996 to 2006 and the power-law for both firms and workers is established. The demand index. is evaluated in the manufacturing sector. A new discovery is reported for the nonmanufacturing (service) sector, which calls for an expansion of the superstatistics framework to include the negative temperature range.

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  • Distribution of Labour Productivity in Japan over the Period 1996-2006 査読

    Wataru Souma, Yuichi Ikeda, Hiroshi Iyetomi, Yoshi Fujiwara

    ECONOMICS-THE OPEN ACCESS OPEN-ASSESSMENT E-JOURNAL3   2009年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:KIEL INST WORLD ECONOMY  

    The distribution of labour productivity is investigated by analyzing the longitudinal micro-level data set which contains the detailed financial conditions of large numbers of Japanese companies over the period 1996-2006. The authors show that the distribution of labour productivity in both the high and low productivity ranges follows a power law distribution. The generalized beta function of the second kind, which asymptotically reproduces a power law function, is applied to explain the distribution of labour productivity. By comparing the power law exponents that characterize high and low productivity ranges, the authors show that for manufacturing industries, inequality in the low productivity range is larger than that in the high productivity range. For the manufacturing industries, the authors also clarify that the change of inequality in the low productivity range has strong correlation with GDP. In addition, by comparing the power law exponents of the high productivity range in the manufacturing and non-manufacturing industries, the authors show that the inequality of the non-manufacturing industry is higher than that of the manufacturing industry.

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  • Structure and Temporal Change of the Credit Network between Banks and Large Firms in Japan 査読

    Yoshi Fujiwara, Hideaki Aoyama, Yuichi Ikeda, Hiroshi Iyetomi, Wataru Souma

    ECONOMICS-THE OPEN ACCESS OPEN-ASSESSMENT E-JOURNAL3   2009年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:KIEL INST WORLD ECONOMY  

    We present a new approach to understanding credit relationships between commercial banks and quoted firms, and with this approach, examine the temporal change in the structure of the Japanese credit network from 1980 to 2005. At each year, the credit network is regarded as a weighted bipartite graph where edges correspond to the relationships and weights refer to the amounts of loans. Reduction in the supply of credit affects firms as debtor, and failure of a firm influences banks as creditor. To quantify the dependency and influence between banks and firms, we propose a set of scores of banks and firms, which can be calculated by solving an eigenvalue problem determined by the weight of the credit network. We found that a few largest eigenvalues and corresponding eigenvectors are significant by using a null hypothesis of random bipartite graphs, and that the scores can quantitatively describe the stability or fragility of the credit network during the 25 years.

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  • Modeling of Relation between Transaction Network and Production Activity for Firms 査読

    Takashi Iino, Hiroshi Iyetomi

    PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT ( 179 ) 134 - 144   2009年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PROGRESS THEORETICAL PHYSICS PUBLICATION OFFICE  

    Bak et al. [Ricerche Economiche 47 (1993), 3] proposed a self-organizing model for production activity of interacting firms to illustrate how large fluctuations can be triggered by small independent shocks in aggregate economy. This paper develops the original transaction model based on a regular network with layered order flow to accommodate more realistic networks. Simulations in the generalized model so obtained are then carried out for various networks to examine the influence caused by change of the network structure.

    DOI: 10.1143/PTPS.179.134

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  • Random Matrix Theory of Dynamical Cross Correlations in Financial Data 査読

    Yasuhiro Nakayama, Hiroshi Iyetomi

    PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT ( 179 ) 60 - 70   2009年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PROGRESS THEORETICAL PHYSICS PUBLICATION OFFICE  

    A new method taking advantage of the random matrix theory is proposed to extract genuine dynamical correlations between price fluctuations of different stocks. One-day returns of 557 Japanese major stocks for the 11-year period from 1996 to 2006 are used for this study. We carry out, the discrete Fourier transform of the returns to construct a correlation matrix at each frequency. Also we prepare series of random numbers which are mutually uncorrelated and hence serve as a reference. Comparison of the eigenvalues of the empirical correlation matrix with the reference results of the random one enables us to distinguish between information and noise involved in complicated behavior of the stock returns. It is thus demonstrated that there exist collective motions of the stock prices with periods well over days. Finally we indicate a possible application of the present finding to the risk evaluation of portfolios.

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  • Agent-Based Model Approach to Complex Phenomena in Real Economy 査読

    Hiroshi Iyetomi, Hideaki Aoyama, Yoshi Fujiwara, Yuichi Ikeda, Wataru Souma

    PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT ( 179 ) 123 - 133   2009年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PROGRESS THEORETICAL PHYSICS PUBLICATION OFFICE  

    An agent-based model for firms' dynamics is developed. The model consists of firm agents with identical characteristic parameters and a bank agent. Dynamics of those agents are described by their balance sheets. Each firm tries, to maximize its expected profit with possible risks in market. Infinite growth of a firm directed by the "profit maximization" principle is suppressed by a concept of "going concern". Possibility of bankruptcy of firms is also introduced by incorporating a retardation effect of information on firms' decision. The firms, mutually interacting through the monopolistic bank, become heterogeneous in the course of temporal evolution. Statistical properties of firms' dynamics obtained by simulations based on the model are discussed in light of observations in the real economy.

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  • Econophysics - Physical Approach to Social and Economic Phenomena - Preface 査読

    Hideaki Aoyama, Yoshi Fujiwara, Hiroshi Iyetomi, Aki-Hiro Sato

    PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT ( 179 ) I - II   2009年

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    記述言語:英語   出版者・発行元:PROGRESS THEORETICAL PHYSICS PUBLICATION OFFICE  

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  • Labour Productivity Superstatistics 査読

    Hideaki Aoyama, Hiroshi Yoshikawa, Hiroshi Iyetomi, Yoshi Fujiwara

    PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT ( 179 ) 80 - 92   2009年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PROGRESS THEORETICAL PHYSICS PUBLICATION OFFICE  

    We discuss superstatistics theory of labour productivity. Productivity distribution across workers, firms and industrial sectors are studied empirically and found to obey power-distributions, in sharp contrast to the equilibrium theories of mainstream economics. The Pareto index is found to decrease with the level of aggregation, i.e,, from workers to firms and to industrial sectors. In order to explain these phenomenological laws, we propose a superstatistics framework, where the role of the fluctuating temperature is played by the fluctuating demand.

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  • Correlated performance of firms in a transaction network 査読

    Yuichi Ikeda, Hideaki Aoyama, Hiroshi Iyetomi, Yoshi Fujiwara, Wataru Souma

    JOURNAL OF ECONOMIC INTERACTION AND COORDINATION3 ( 1 ) 73 - 80   2008年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:SPRINGER HEIDELBERG  

    The correlation of firms' performance on a transaction network is studied by analyzing financial and transaction data. Statistically significant correlation coefficients are obtained as evidence for the firm interactions. The firm interactions are taken into account in the basic equation of firm activity. Forty percent of residuals are explained by considering the firm interactions. The overall structure of the transaction network, i.e., the connectivity of industry sectors, is analyzed.

    DOI: 10.1007/s11403-008-0035-5

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  • Energetics of interlayer binding in graphite: The semiempirical approach revisited 査読

    Masayuki Hasegawa, Kazume Nishidate, Hiroshi Iyetomi

    PHYSICAL REVIEW B76 ( 11 )   2007年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER PHYSICAL SOC  

    We have developed a semiempirical method to obtain interlayer binding energy of graphite in the previous work [M. Hasegawa and K. Nishidate, Phys. Rev. B 70, 205431 (2004)]. In the present paper, we revisit this approach and develop an improved method, in which ab initio calculations based on the density functional theory (DFT) are also corrected through an empirical atom-atom van der Waals (vdW) interaction. The local density approximation (LDA) and generalized gradient approximation (GGA) are used in the DFT calculations. The parametrized damping function introduced to modify the asymptotic atom-atom vdW interaction is more flexible than the previous ones and covers a wider range of possibility in correcting for the approximate DFT calculations. The damping function is determined empirically by imposing the condition that the experimental interlayer spacing, in-plane lattice constant, and c-axis elastic constant are reproduced. We also require consistency between the LDA- and GGA-based methods (LDA+vdW, GGA+vdW) as the theoretically motivated necessary condition. The interlayer binding energy obtained by this method is 60.4 meV/atom at T=0 K. The result of similar to 54 meV/atom at room temperature corrected by the thermal effect is consistent with the most recent experiment, 52 +/- 5 eV/atom [R. Zacharia , Phys. Rev. B 69, 155406 (2004)]. The atom-atom vdW interaction obtained by the present semiempirical method favorably corrects for the overbinding and underbinding nature of the LDA and GGA, respectively, in the in-plane energetics of graphite. That interaction also provides a useful starting point for the studies of energetics of other graphitic systems such as fullerenes and carbon nanotubes.

    DOI: 10.1103/PhysRevB.76.115424

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  • Response of firm agent network to exogenous shock 査読

    Yuichi Ikeda, Hideaki Aoyama, Hiroshi Iyetomi, Yoshi Fujiwara, Wataru Souma, Taisel Kaizoji

    PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS382 ( 1 ) 138 - 148   2007年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    This paper describes an agent-based model of interacting firms, in which interacting firm agents rationally invest capital and labor in order to maximize payoff. Both transactions and production are taken into account in this model. First, the performance of individual firms on a real transaction network was simulated. The simulation quantitatively reproduced the cumulative probability distribution of revenue, material cost, capital, and labor. Then, the response of the firms to a given exogenous shock, defined as a sudden change of gross domestic product, is discussed. The longer tail in cumulative probability and skewed distribution of growth rate are observed for a high growth scenario. (C) 2007 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.physa.2007.02.016

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  • Quantitative agent-based firm dynamics simulation with parameters estimated by financial and transaction data analysis 査読

    Yuichi Ikeda, Wataru Souma, Hideaki Aoyama, Hiroshi Iyetomi, Yoshi Fujiwara, Taisel Kaizoji

    PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS375 ( 2 ) 651 - 667   2007年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    Firm dynamics on a transaction network is considered from the standpoint of econophysics, agent-based simulations, and game theory. In this model, interacting firms rationally invest in a production facility to maximize net present value. We estimate parameters used in the model through empirical analysis of financial and transaction data. We propose two different methods (analytical method and regression method) to obtain an interaction matrix of firms. On a subset of a real transaction network, we simulate firm's revenue, cost, and fixed asset, which is the accumulated investment for the production facility. The simulation reproduces the quantitative behavior of past revenues and costs within a standard error when we use the interaction matrix estimated by the regression method, in which only transaction pairs are taken into account. Furthermore, the simulation qualitatively reproduces past data of fixed assets. (c) 2006 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.physa.2006.10.005

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  • Correlation in business networks 査読

    Wataru Souma, Hideaki Aoyama, Yoshi Fujiwara, Yuichi Ikeda, Hiroshi Iyetomi, Taisei Kalzoji

    PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS370 ( 1 ) 151 - 155   2006年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    This paper considers business networks. Through empirical study, we show that business networks display characteristics of small-world networks and scale-free networks. In this paper, we characterize firms as sales and bankruptcy probabilities. A correlation between sales and a correlation between bankruptcy probabilities in business networks are also considered. The results reveal that the correlation between sales depends strongly on the type of network, whereas the correlation between bankruptcy probabilities does so only weakly. (c) 2006 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.physa.2006.04.040

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  • Intercluster interaction of TiO2 nanoclusters using variable-charge interatomic potentials 査読

    S Ogata, H Iyetomi, K Tsuruta, F Shimojo, RK Kalia, A Nakano, P Vashishta

    NANOPHASE AND NANOCOMPOSITE MATERIALS III581   667 - 672   2000年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:MATERIALS RESEARCH SOCIETY  

    A new interatomic potential has been developed for molecular-dynamics simulations of TiO2 based on the formalism of Streitz and Mintmire [J. Adhesion Sci. Technol. 8, 853 (1994)], in which atomic charges vary dynamically according to the generalized electronegativity-equalization principle. The present potential reproduces various quantities of rutile crystal including vibrational density of states, static dielectric constants, melting temperature, elastic moduli, and surface relaxation. Calculated cohesive-energy and dielectric constants for anatase crystal agree well with experimental data The potential is applied to TiO2 nanoclusters (size 60-80 Angstrom) for both anatase and rutile phases to analyze their equilibrium configuration and space-charge distribution. Stable double-charge layer is found in the surface region of a spherical nanocluster for both rutile and anatase, resulting in enhanced Coulomb-repulsion between the nanoclusters at close proximity.

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  • Variable-charge molecular dynamics of aggregation of TiO2 nanocrystals 査読

    S Ogata, H Iyetomi, K Tsuruta, F Shimojo, A Nakano, RK Kalia, P Vashishta

    GRAIN BOUNDARY ENGINEERING IN CERAMICS - FROM GRAIN BOUNDARY PHENOMENA TO GRAIN BOUNDARY QUANTUM STRUCTURES118   79 - 86   2000年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:AMER CERAMIC SOC  

    Molecular dynamics (MD) simulations of both rutile and anatase TiO2-nanoclusters (size 60-80 Angstrom) are performed using an environment-dependent interatomic potential developed recently by Ogata et al. [J. Appl. Phys. 86 [16], 3036-3041 (1999)]. In the potential, atomic charges vary dynamically according to the generalized electronegativity-equalization principle. Formation of double-charge layer and enhanced atomic diffusion are observed in surface regions of the free TiO2-nanospheres by inclusion of the atomic-charge variation. Their effects on aggregation processes of TiO2 nanoclusters are investigated through MD simulations.

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  • Band-theoretical approach to the superionic conductivity of solid electrolytes 査読

    H Kikuchi, H Iyetomi, A Hasegawa

    COMPUTER-AIDED DESIGN OF HIGH-TEMPERATURE MATERIALS   393 - 401   1999年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:OXFORD UNIV PRESS  

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  • ATOMIC-SIZE EFFECTS ON MEDIUM-RANGE ORDER IN GLASSES 査読

    H IYETOMI, P VASHISHTA

    PHYSICAL REVIEW B47 ( 6 ) 3063 - 3069   1993年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER PHYSICAL SOC  

    Effects of atomic sizes on structural correlations in AX2-type disordered systems such as SiO2, GeSe2, and Ag2Se are studied using a charged-hard-sphere model and the hypernetted-chain scheme. Structural change is elucidated as a function of the size ratio through the first sharp diffraction peak in the number-number structure factor (medium-range correlations), the A-X coordination [formation of A(X1/2)4 tetrahedra], and the principal peak in the charge-charge structure factor (charge ordering). We find a gradual change from SiO2-type to Ag2Se-type disordered structure in the range of 0.5 < R < 1.0, where R (=sigma(A)/sigma(X)) is a ratio of the steric radius of A species to that of X species. As R increases, the medium-range order, which is closely related to the formation of A(X1/2)4 tetrahedra, disappears. In the transition region frustration between the steric and Coulombic interactions depresses the charge ordering.

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  • INTEGRAL-EQUATION APPROACH TO MEDIUM-RANGE ORDER IN MOLTEN AND GLASSY CHALCOGENIDES 査読

    H IYETOMI, P VASHISHTA, RK KALIA

    PHYSICAL REVIEW B43 ( 2 ) 1726 - 1734   1991年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER PHYSICAL SOC  

    The first sharp diffraction peak (FSDP), a signature of medium-range order in molten and vitreous chalcogenides, is investigated using the integral-equation method. A variety of interatomic potentials, including uncharged and charged hard spheres, and realistic two-body interactions, are used in this study. The two-body potential consists of steric repulsions, Coulomb interactions due to charge-transfer effects, and the effects of electronic polarizability of ions. GeSe2 is treated as a specific example. The FSDP is observed in both the charged-hard-sphere and the realistic two-body interaction models. In both models steric and charge-transfer effects are found to give rise to Ge(Se1/2)4 tetrahedra whose packing determines the medium-range order and the attendant FSDP. From the charge-charge structure factor it is found that the FSDP arises from spatial correlations where charge neutrality prevails. The nature of the medium-range correlation is elucidated through the temperature and density dependence of the FSDP and the thermal expansion determined from the shifts of the peaks in the static structure factor. We have also studied the effects of the potential parameters on the position of the FSDP. The results of the hypernetted-chain theory are compared with the molecular-dynamics results.

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  • DENSITY-FUNCTIONAL THEORY OF 3-BODY INTERACTIONS IN LIQUIDS AND GLASSES 査読

    H IYETOMI, P VASHISHTA

    SOLID STATE IONICS32-3   959 - 961   1989年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

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書籍等出版物

  • The hitchhiker's guide to the economy : proceedings of the YITP Workshop on Econophysics, Kyoto, Japan, July 15-16, 2011

    The YITP workshop, 青山, 秀明, 藤原, 義久, 家富, 洋, 佐藤, 彰洋

    Publication Office, Progress of Theoretical Physics  2012年 

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    総ページ数:vii, 222 p.   記述言語:英語

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  • Econophysics : physical approach to social and economic phenomena : proceedings of the YITP workshop on econophysics, Kyoto, Japan, December 24-25, 2007

    The YITP workshop (2007 : Kyoto, Japan), 青山, 秀明, 藤原, 義久, 家富, 洋, 佐藤, 彰洋

    Progress of Theoretical Physics  2009年 

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    総ページ数:vii, 226 p.   記述言語:英語

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  • 経済物理学 = Econophysics

    青山, 秀明, 家富, 洋, 池田, 裕一, 相馬, 亘, 藤原, 義久

    共立出版  2008年10月  ( ISBN:9784320096394

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    総ページ数:viii, 442p   記述言語:日本語

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  • パレート・ファームズ : 企業の興亡とつながりの科学

    青山, 秀明, 家富, 洋, 池田, 裕一, 相馬, 亘, 藤原, 義久

    日本経済評論社  2007年5月  ( ISBN:9784818819504

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    総ページ数:xv, 370p   記述言語:日本語

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  • Construction of a microscopic agent-based model for firms' dynamics

    Modelling Cooperative Behavior in the Social Sciences (AIP, New York)  2005年 

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  • 変分APW法の開発と超イオン伝導物質の電子状態解析

    家富, 洋

    [家富洋]  2002年3月 

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    総ページ数:1冊  

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  • Initial stages of sintering of TiO<sub>2</sub> nanoparticles: Variable-charge moleiular dynamics

    Mat. Res. Soc. Symp. Proc  2001年 

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  • Sintering of TiO2 nanoparticles: Variable-charge molecular dynamics on PC clusters

    Materials Science for the 21st Century  2001年 

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  • p-d Hybridization in Superionic Conductors(共著)

    Statistical Physics : Third Tohwa University International Conference, edited by M. Tokuyama and H. E. Stanley(AIP)  2000年 

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  • Intercluster interaction of TiO<sub>2</sub> nanoclusters using variable-charge interatomic potentials(共著)

    Mater. Res. Soc. Symp. Proc.  2000年 

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  • Variable-charge molecular-dynamics of aggregation of TiO<sub>2</sub> nanocrystals(共著)

    Ceramics Transactions "Grain Boundary Engineering in Ceramics"(The American Ceramic Society)  2000年 

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  • チェイキン&ルベンスキー現代の凝縮系物理学(下)(共訳)

    吉岡書店  2000年 

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  • チェイキン&ルベンスキー現代の凝縮系物理学(上)(共訳)

    吉岡書店  2000年 

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  • Development of a variational augmented plane wave method and its application to the electronic structure of ionic compounds(共著)

    Computer-Aided Design of High-Temperature Materials, edited by A. Pechenik, R. K. Kalia and P. Vashishta(Oxford Univ. Press, New York)  1999年 

     詳細を見る

  • Band-theoretical approach to the superionic conductivity of solid electrolytes(共著)

    Computer-Aided Design of High-Temperature Materials, edited by A. Pechenik, R. K. Kalia and P. Vashishta(Oxford Univ. Press, New York)  1999年 

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  • Electronic properties and mechanism of superionic conductivity in solid electrolytes(共著)

    Strongly Coupled Coulomb Systems, edited by G. J. Kalman, K. Blagoev, and J. M. Rommel(Plenum Press, New York)  1998年 

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  • 高密度多種イオンプラズマの相構造、電子状態および原子・分子過程

    一丸, 節夫, 家富, 洋

    一丸節夫  1992年 

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    総ページ数:35p  

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  • Thermonuclear reaction rates of dense carbon-oxygen mixture in white dwarfs(共著)

    Strongly Coupled Plasma Physics  1990年 

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  • Hypernetted chain analyses of dense plasmalike materials(共著)

    Condensed Matter Theories  1987年 

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  • Thermodynamic functions, transport coefficients and dynamic correlations in dense plasmas(共著)

    Strongly Coupled Plasma Physics  1987年 

     詳細を見る

  • Statistical physics of dense plasmas : thermodynamics, transport coefficients and dynamic correlations

    一丸, 節夫, 田中, 成典, 家富, 洋

    一丸 節夫  1986年 

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    総ページ数:iv, 272 p.   記述言語:英語

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  • Transport properties of dense matter(共著)

    Proc. The 3rd Marcel Grossmann Meeting on General Relativity(North-Holland, 1983)  1983年 

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MISC

  • Econophysics and companies: Statistical life and death in complex business networks

    Hideaki Aoyama, Yoshi Fujiwara, Yuichi Ikeda, Hiroshi Iyetomi, Wataru Souma

    Econophysics and Companies: Statistical Life and Death in Complex Business Networks   1 - 234   2010年1月

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    記述言語:英語   出版者・発行元:Cambridge University Press  

    Econophysics is an emerging interdisciplinary field that takes advantage of the concepts and methods of statistical physics to analyse economic phenomena. This book expands the explanatory scope of econophysics to the real economy by using methods from statistical physics to analyse the success and failure of companies. Using large data sets of companies and income-earners in Japan and Europe, a distinguished team of researchers show how these methods allow us to analyse companies, from huge corporations to small firms, as heterogeneous agents interacting at multiple layers of complex networks. They then show how successful this approach is in explaining a wide range of recent findings relating to the dynamics of companies. With mathematics kept to a minimum, the book is not only a lively introduction to the field of econophysics but also provides fresh insights into company behaviour.

    DOI: 10.1017/CBO9780511761157

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  • QEq型原子間ポテンシャルを用いたナノフェイズ材料のシミュレーション

    機能材料25 ( 11 ) 29 - 34   2005年

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  • Mechanism of Impurity Diffusion in Silicon with a Point Defect: Tight-Binding Molecular Dynamics Simulation

    Trans. MRS-JVol. 12, pp. 3631-3634   2004年

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  • Phase characteristics and elastic properties of binary Coulomb compounds

    T Igarashi, H Iyetomi

    JOURNAL OF PHYSICS A-MATHEMATICAL AND GENERAL36 ( 22 ) 6197 - 6206   2003年6月

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    記述言語:英語   出版者・発行元:IOP PUBLISHING LTD  

    We have already shown that binary Coulomb compounds in disordered states are stabilized against phase separation in a minor ion rich region as charge asymmetry is enhanced; a stable phase appears approximately beyond the charge ratio R-Z = 6. In this paper, the mechanical properties of the stable compounds are elucidated through extensive calculations of the Coulomb energy increments due to virtual deformations. The compounds turn out to be much more isotropic than the mixed pure crystals in the linear response regime. And their effective elastic constants obtained by averaging over directions are well expressible in terms of those of the pure crystals. The compounds, however, show fragile behaviour at the degree of deformation where the pure crystal still retains its elasticity.

    DOI: 10.1088/0305-4470/36/22/348

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  • p-d hybridization in superionic conductors

    M Kobayashi, S Ono, T Kohda, H Iyetomi, S Kashida, T Tomoyose

    SOLID STATE IONICS154   209 - 215   2002年12月

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    記述言語:英語   出版者・発行元:ELSEVIER SCIENCE BV  

    The band calculations of AgX (X=halogen), CuX (X=halogen) and beta-Ag3SX (X=I, Br) are studied to reveal the high ionic conductivity of Ag+ and Cu+ in these superionic conductors using the linear combination of atomic orbitals (LCAO) theory. It is found that the d states of Ag+ are much more weakly coupled with the p states of halogen ions, while those of Cu+ are much more strongly coupled with the p bands. The strength of p-d hybridization is discussed to connect with the activation energy for the ionic conduction. It is shown that the high ionic conductivity of AgX (X=halogen) and beta-Ag3SX (X=I, Br) primarily stems from the combination of the deformability of d shell and the weakness of p-d hybridization. (C) 2002 Elsevier Science B.V All rights reserved.

    DOI: 10.1016/S0167-2738(02)00434-4

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  • Coulombic Insight into Charge Ordering in Yb4As3 and Sm3Te4 査読

    Hiroshi Iyetomi, Hideto Higashi, Yuichi Nemoto, Terutaka Goto

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN71   306 - 308   2002年1月

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    記述言語:英語   出版者・発行元:PHYSICAL SOC JAPAN  

    Charge ordering in Yb4As3 and Sm3Te4, complementary f-electron compounds with the same crystalline structure, is investigated on the basis of a Coulomb lattice gas model; the Coulomb interactions between ions are fully taken into account within a classical treatment. The Madelung energy of the system at finite temperatures is calculated with a Monte Carlo (MC) method simulating the Boltzmann distribution of multivalent cations on equivalent lattice sites. The unit cell for the MC simulations is extended to contain 32 molecular formulas in it. The model is successful in distinguishing the two mixed-valence compounds with different, characteristics of charge ordering. Yb4As3 shows a phase transition (Verwey transition) due to charge ordering while Sm3Te4 continuously freezes into a glassy state on cooling.

    DOI: 10.1143/JPSJS.71S.306

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  • Collaborative Simulation Grid: Multiscale Quantum-Mechanical/Classical Atomistic Simulations on Distributed PC Clusters in the US and Japan

    Proc. Supercomputing 2002pp. 1-8   2002年

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  • p-d hybridization and superionicity in silver ternary compounds

    T Kohda, S Ono, M Kobayashi, H Iyetomi, S Kashida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN70 ( 9 ) 2689 - 2693   2001年9月

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    記述言語:英語   出版者・発行元:PHYSICAL SOC JAPAN  

    The tight-binding electronic band calculations of beta -Ag3SX (X=I, Br) are carried out in order to clarify the high ionic conductivity of silver ions The d bands of Ag ions are much more weakly coupled with the p bands of halogen ions, than with the p bands of S ions. The strength of p-d hybridization is discussed to connect with the activation energy for the ionic conduction. It is shown that the high ionic conductivity of beta -Ag3SX (X=I, Br) primarily stems from the weakness of the p-d hybridization.

    DOI: 10.1143/JPSJ.70.2689

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  • Difference of p-d hybridization in noble metal halides

    S. Ono, M. Kobayashi, H. Iyetomi, T. Tomoyose

    Solid State Ionics139 ( 3-4 ) 249 - 254   2001年2月

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    記述言語:英語  

    The band calculations of noble metal halides are studied to reveal the high ionic conductivity of Ag+ and Cu+ in noble metal halides using the linear combination of atomic orbitals (LCAO) theory. It is found that the d states of Ag+ are much more weakly coupled with the p states of halogen ions, while those of Cu+ are much more strongly coupled with the p bands. The strength of p-d hybridization is discussed in relation to the activation energy for the ionic conduction. It is shown that the high ionic conductivity of AgX (X = halogen) primarily stems from the combination of the deformability of the d shell and the weakness of p-d hybridization.

    DOI: 10.1016/S0167-2738(00)00824-9

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  • Chemical stability of binary Coulomb compounds

    T Igarashi, N Nakao, H Iyetomi

    CONTRIBUTIONS TO PLASMA PHYSICS41 ( 4 ) 319 - 322   2001年

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    記述言語:英語   出版者・発行元:WILEY-V C H VERLAG GMBH  

    Chemical stability of binary Coulomb compounds is studied through extensive calculation of their Madelung energies. A remarkable finding is that the compounds with disordered ionic arrangements in a certain range of the composition are stable against chemical separation beyond the charge ratio around 6; clearly the entropic effect due to finite temperature promotes the mixing of ions of different species. For the ordered AB(3)-type compounds, there exists a crystalline structure which is more chemically bounded than that of Dyson (1971). Relative stability of the ordered and disordered compounds is also discussed.

    DOI: 10.1002/1521-3986(200107)41:4<319::AID-CTPP319>3.0.CO;2-J

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  • ナノ材料シミュレーションの最近の展開(共著)

    マテリアルインテグレーション14 ( 1 ) 3 - 8   2001年

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  • Initial stages of sintering of TiO2 nanoparticles: Variable-charge molecular dynamics simulations

    S. Ogata, H. Iyetomi, K. Tsuruta, F. Shimojo, A. Nakano, P. Vashishta, R. K. Kalia, C.-K. Loong

    Mat. Res. Soc. Symp. Proc.   2001年

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  • Sintering of TiO2 Nanoparticles: Variable-Charge Molecular Dynamics on PC clusters

    Shuji Ogata, Hiroshi Iyetomi, Kenji Tsuruta, Fuyuki Shimojo

    International Simposia on Materials Science for the 21st Century   2001年

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  • Role of atomic charge transfer on sintering of TiO2 nanoparticles: Variable-charge molecular dynamics

    S Ogata, H Iyetomi, K Tsuruta, F Shimojo, A Nakano, RK Kalia, P Vashishta

    JOURNAL OF APPLIED PHYSICS88 ( 10 ) 6011 - 6015   2000年11月

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    記述言語:英語   出版者・発行元:AMER INST PHYSICS  

    The stability of surface structure and space-charge distribution in free TiO2 nanoparticles are investigated for both rutile and anatase phases using a variable-charge interaction potential in which atomic charges vary dynamically depending on their environment. We find the dynamic charge transfer: (i) enhances atomic diffusion at surfaces of the spherical nanoparticles at high temperatures; and (ii) creates additional repulsive force between the two nanospheres through formation of a double-charge surface layer in each nanosphere. The surface diffusion due to the charge transfer clearly distinguishes the two nanospheres with different underlying crystalline structures; the surface diffusion constant of the anatase sphere is almost three times as great as that of the rutile sphere. Variable-charge molecular dynamics simulations are then applied to sintering of two TiO2 nanospheres. It turns out that the enhanced surface diffusion in the anatase nanosphere at high temperatures significantly promotes neck formation between the two spheres. (C) 2000 American Institute of Physics. [S0021-8979(00)08323-7].

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  • Incipient phase separation in Ag/Ge/Se glasses: clustering of Ag atoms

    H Iyetomi, P Vashishta, RK Kalia

    JOURNAL OF NON-CRYSTALLINE SOLIDS262 ( 1-3 ) 135 - 142   2000年2月

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    記述言語:英語   出版者・発行元:ELSEVIER SCIENCE BV  

    Structural and dynamical properties of three-component chalcogenide glasses, Ag/Ge/Se, are studied using the molecular dynamics (MD) method. Effective potentials for GeSe2 and Ag2Se, which have already been well characterized, are combined to describe the interatomic interactions in the ternary system. The MD results for bond lengths, the static structure factor, and the vibrational density of states are in good agreement with neutron-scattering results. Our results elucidate the role played by silver ions as network modifiers in glass-forming GeSe2 with the medium-range correlations. Upon cooling we observe clustering of Ag atoms which indicates a tendency toward phase separation. (C) 2000 Published by Elsevier Science B.V. All rights reserved.

    DOI: 10.1016/S0022-3093(99)00692-4

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  • Modification of the network structure in multicomponent oxide glasses by metal ions(共著)

    Trans. MRS-J25 ( 4 ) 1025 - 1028   2000年

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  • Variable-charge interatomic potentials for molecular-dynamics simulations of TiO2

    S Ogata, H Iyetomi, K Tsuruta, F Shimojo, RK Kalia, A Nakano, P Vashishta

    JOURNAL OF APPLIED PHYSICS86 ( 6 ) 3036 - 3041   1999年9月

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    記述言語:英語   出版者・発行元:AMER INST PHYSICS  

    An interatomic potential model has been developed for molecular-dynamics simulations of TiO2 (rutile) based on the formalism of Streitz and Mintmire [J. Adhes. Sci. Technol. 8, 853 (1994)], in which atomic charges vary dynamically according to the generalized electronegativity equalization principle. The present model potential reproduces the vibrational density of states, the pressure-dependent static dielectric constants, the melting temperature, and the surface relaxation of the rutile crystal, as well as the cohesive energy, the lattice constants, and the elastic moduli. We find the physical properties of rutile are significantly affected by dynamic charge transfer between Ti and O atoms. The potential allows us to perform atomistic simulations on nanostructured TiO2 with various kinds of interfaces (surfaces, grain boundaries, dislocations, etc.). (C) 1999 American Institute of Physics. [S0021-8979(99)07618-5].

    DOI: 10.1063/1.371165

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  • Statistical Physics of Dense Plasma Materials : Metallic Hydrogen

    Journal of Plasma and Fusion Research75 ( 9 ) 1037 - 1044   1999年

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  • 高密度プラズマ物質の統計物理-金属水素を中心に-(共著)

    プラズマ・核融合学会誌75 ( 9 ) 1037 - 1044   1999年

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  • Band theoretical study on the electronic structure of AgI in the γ-phase(共著)

    Activity report of the Supercomputer Center of the Institute for Solid State Physics of the University of Tokyo   95 - 96   1998年

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  • Surface states in-wave superconductors

    Xin-Zhong Yan, Hiroshi Iyetomi

    Physical Review B - Condensed Matter and Materials Physics57 ( 13 ) 7944 - 7949   1998年

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    記述言語:英語  

    On the basis of a two-dimensional tight-binding model, the eigenstates of quasiparticles in a (Formula presented)-wave superconductor with a (110)\\ surface at the ground state, (Formula presented) K, are investigated through self-consistently solving the Bogoliubov-de Gennes equation. The order parameter is considerably suppressed near the surface. The existence of bound surface states critically depends on a parameter (Formula presented) (the parallel component of the wave number vector to the surface). Besides the midgap states which exist in regions (Formula presented) and (Formula presented), it is found that at (Formula presented) with (Formula presented) or (Formula presented), there can also appear a number of surface states with nonzero energies. The parameters (Formula presented) and (Formula presented) are close to the Fermi wave number (Formula presented) in the (Formula presented) direction, and (Formula presented). © 1998 The American Physical Society.

    DOI: 10.1103/PhysRevB.57.7944

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  • The p-d hybridization in the electronic structure of α-Ag2Te

    H. Kikuchi, H. Iyetomi, A. Hasegawa

    Journal of Physics Condensed Matter9 ( 28 ) 6031 - 6048   1997年7月

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    記述言語:英語  

    The electronic structure of αAg2Te is discussed, with special attention paid to possible roles of the p-d hybridization, on the basis of density functional calculations in the local-density approximation
    α-Ag2Te is a typical superionic conductor, and also exhibits interesting electronic properties. Fully self-consistant calculations based on the energy variational principle are carried out for a hypothetical crystalline compound, Ag2Te with the antiflourite structure, making use of the linearized augmented-plane-wave method. The calculated equilibrium lattice constant agree with a measured value within an accuracy of 5%. The self-consistent determination of the relative sizes of the augmented-plane-wave spheres leads to an energy band structure similar to that of a narrow-gap semiconductor, in accordance with experiments. Also, the magnitudes predicted for the effective masses of the electrons and holes are almost within the experimental uncerainties. Such quantitative agreement even with the static model arises from the following facts: (i) the Ag d states and the Te p states are not hybridized to such an extent as to have a significant influence on the band-structure characteristics near the energy gap
    and (ii) the lowest conduction band consists mainly of Ag and Te s states with extended character. Thus the p-d hybridization can hardly be considered to be the mechanism that induces the superionic conductivity in α-Ag2Te.

    DOI: 10.1088/0953-8984/9/28/003

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  • Electromic properties and mechanism of superionic conductivity in solid electrolytes(共著)

    Activity Report of the Supercomputer Center of the Institute for Solid State Physics of the University of Tokyo   48 - 49   1997年

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  • Role of the p-d hybridization in the onset of the superionic conductivity(共著)

      37 ( 3 ) 26 - 27   1997年

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  • Analysis of deposit profiles for SiO<sub>2</sub> gap fill process by using fias-ECR-CVD systems

    Proceedings of the 18th Dry Process Symposium   99 - 104   1996年

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  • Electronic properties and mechanism of superionic conductivity in solid electrolytes

    Activity Report of the Supercomputer Center of the Institute for Solid State Physics of the University of Tokyo   59 - 60   1996年

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  • Density-functional study of antiferromagnetic spin correlations in layered electrons: Conductive spin-density-wave states

    Hiroshi Iyetomi, Setsuo Ichimaru

    Physical Review B49 ( 17 ) 11900 - 11909   1994年

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    記述言語:英語  

    It is shown in the density-functional theory that a two-dimensional (2D) layer of electrons may have an inhomogeneous spin-density-wave (SDW) ground state, induced by 2 net attraction between nearest-neighbor electrons with antiparallel spins due to the exchange-correlation potentials stemming from the second-order exchange processes. Phase diagrams of the spin-inhomogeneous ground states for such 2D electrons are obtained in terms of the antiferromagnetic order parameters. The results predict that spin-inhomogeneous conductive states exist between the onset of a SDW instability and the eventual antiferromagnetic Mott-insulator states
    analyses of the Fermi-surface structures and the densities of states substantiate that these SDW electrons are itinerant. Stability of those SDW states against thermal fluctuations, spatial modulation due to a lattice field, and hole injection is also examined. It is thus suggested that the conductive SDW states may play a key role in elucidating the microscopic mechanisms of high-temperature superconductivity. © 1994 The American Physical Society.

    DOI: 10.1103/PhysRevB.49.11900

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  • EQUATIONS OF STATE AND PHASE-DIAGRAMS FOR DENSE MULTI-IONIC MIXTURE PLASMAS

    S OGATA, H IYETOMI, S ICHIMARU, HM VANHORN

    PHYSICAL REVIEW E48 ( 2 ) 1344 - 1358   1993年8月

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    記述言語:英語   出版者・発行元:AMERICAN PHYSICAL SOC  

    Equations of state for dense binary-ionic mixture (BIM) plasmas with charge ratios R(Z) less-than-or-equal-to 4.5 are evaluated for both fluid and solid phases on the basis of internal energies calculated by the Monte Carlo (MC) simulation method. The accuracy of the results has been confirmed through a sum-rule analysis of the free energy with respect to screening potentials at zero separation in one-component plasmas. Phase diagrams for various BIM's appropriate to white-dwarf interiors are constructed, including the effects of compressibility of the relativistically degenerate electrons. Eutectic diagrams, which result in significant chemical separation upon solidification, are predicted for BIM's with R(z) greater than or similar to 1.6. Free energies for dense ternary-ionic mixtures are also derived for both fluid and solid phases through comparison of the corresponding MC internal energies and by a sum-rule analysis using BIM screening potentials at zero separation. We apply the results to the process of solidification of C-12-O-16-Ne22 mixtures in the interiors of white dwarfs. We find that chemical separation does indeed occur at solidification, and we obtain the result that nearly pure Ne cores are formed in such white dwarfs, even though Ne is only a trace element in the mixture.

    DOI: 10.1103/PhysRevE.48.1344

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  • QUANTUM MONTE-CARLO SIMULATION STUDY OF FREE-ENERGIES AND MELTING TRANSITIONS IN COULOMB SOLIDS

    H IYETOMI, S OGATA, S ICHIMARU

    PHYSICAL REVIEW B47 ( 18 ) 11703 - 11711   1993年5月

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    記述言語:英語   出版者・発行元:AMERICAN PHYSICAL SOC  

    The free energy of a one-component plasma (OCP) in a bcc crystalline state is calculated by a quantum Monte Carlo (MC) simulation method. The partition function in a Feynman path-integral form is sampled over a semiclassical reference system of 128 MC particles, with quantum fluctuations generated according to the Wigner-Seitz model. Exchange effects are shown to be negligible. Helmholtz-free energies of the Coulomb solid, computed at 48 combinations of density and temperature parameters, are decomposed into harmonic and anharmonic contributions and are fitted to analytic formulas; accuracy of the result is confirmed through comparison with the Wigner-Kirkwood expansions and with the ground-state results. The free-energy formulas are applied for calculation of the melting curves in dense carbon and helium OCP materials, appropriate to interiors of degenerate stars, showing that the melting curves start to deviate from the classical predictions at around rho(m) = 2 X 10(8) g/cm3 (C) and 2 X 10(3) g/cm3 (He), far lower than the values predicted by analyses of the Lindemann type.

    DOI: 10.1103/PhysRevB.47.11703

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  • Quantum Monte Carlo simulation study of free energies and melting transitions in Coulomb solids

    Hiroshi Iyetomi, Shuji Ogata, Setsuo Ichimaru

    Physical Review B47 ( 18 ) 11703 - 11711   1993年

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    記述言語:英語  

    The free energy of a one-component plasma (OCP) in a bcc crystalline state is calculated by a quantum Monte Carlo (MC) simulation method. The partition function in a Feynman path-integral form is sampled over a semiclassical reference system of 128 MC particles, with quantum fluctuations generated according to the Wigner-Seitz model. Exchange effects are shown to be negligible. Helmholtz-free energies of the Coulomb solid, computed at 48 combinations of density and temperature parameters, are decomposed into harmonic and anharmonic contributions and are fitted to analytic formulas
    accuracy of the result is confirmed through comparison with the Wigner-Kirkwood expansions and with the ground-state results. The free-energy formulas are applied for calculation of the melting curves in dense carbon and helium OCP materials, appropriate to interiors of degenerate stars, showing that the melting curves start to deviate from the classical predictions at around ρm=2×108 g/cm3 (C) and 2×103 g/cm3 (He), far lower than the values predicted by analyses of the Lindemann type. © 1993 The American Physical Society.

    DOI: 10.1103/PhysRevB.47.11703

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  • Atomic-size effects on medium-range order in glasses

    H. Iyetomi, P. Vashishta

    Physical Review B47 ( 6 ) 3063 - 3069   1993年

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    記述言語:英語  

    Effects of atomic sizes on structural correlations in AX2-type disordered systems such as SiO2, GeSe2, and Ag2Se are studied using a charged-hard-sphere model and the hypernetted-chain scheme. Structural change is elucidated as a function of the size ratio through the first sharp diffraction peak in the number-number structure factor (medium-range correlations), the A-X coordination [formation of A(X1/2)4 tetrahedra], and the principal peak in the charge-charge structure factor (charge ordering). We find a gradual change from SiO2-type to Ag2Se-type disordered structure in the range of 0.5&lt
    R&lt
    1.0, where R (=σA/σX) is a ratio of the steric radius of A species to that of X species. As R increases, the medium-range order, which is closely related to the formation of A(X1/2)4 tetrahedra, disappears. In the transition region frustration between the steric and Coulombic interactions depresses the charge ordering. © 1993 The American Physical Society.

    DOI: 10.1103/PhysRevB.47.3063

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  • BRIDGE FUNCTIONS AND IMPROVEMENT ON THE HYPERNETTED-CHAIN APPROXIMATION FOR CLASSICAL ONE-COMPONENT PLASMAS

    H IYETOMI, S OGATA, S ICHIMARU

    PHYSICAL REVIEW A46 ( 2 ) 1051 - 1058   1992年7月

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    記述言語:英語   出版者・発行元:AMER PHYSICAL SOC  

    Bridge functions, the neglected terms in the hypernetted-chain (HNC) theory of classical fluids, are extracted with high precision from Monte Carlo (MC) simulation data for classical one-component plasmas. The MC bridge functions are extended by the use of the exact short-range Widom expansion and of long-range boundary conditions arising from the compressibility sum rule. An explicit analytic expression for the bridge functions is then obtained, leading to improvement on the HNC scheme. Accuracy of the improved HNC scheme is confirmed through comparison with the MC results and by examination of the thermodynamic consistency. The extracted bridge functions are compared with those of other theoretical schemes.

    DOI: 10.1103/PhysRevA.46.1051

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  • ACCURACY OF A DENSITY-WAVE THEORY FOR COULOMB SOLIDS

    H IYETOMI, S ICHIMARU

    PHYSICAL REVIEW B45 ( 1 ) 437 - 439   1992年1月

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    記述言語:英語   掲載種別:記事・総説・解説・論説等(学術雑誌)   出版者・発行元:AMERICAN PHYSICAL SOC  

    The accuracy of a density-wave theory for Coulomb solids is examined in light of "exact" Monte Carlo data; a classical one-component plasma (OCP) and a binary ionic mixture (BIM) of carbon and oxygen are studied. For the OCP, the theory reproduces the solid free energy with excellent accuracy in a broad range of the Coulomb coupling parameter covering the crystallization conditions. For the BIM, we find local charge neutrality, which was not taken into account in previous calculations, plays a crucial role in describing the alloying nature; a phase diagram for the mixture is presented.

    DOI: 10.1103/PhysRevB.45.437

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  • THE SHEAR MODULUS OF THE NEUTRON-STAR CRUST AND NONRADIAL OSCILLATIONS OF NEUTRON-STARS

    T STROHMAYER, S OGATA, H IYETOMI, S ICHIMARU, HM VANHORN

    ASTROPHYSICAL JOURNAL375 ( 2 ) 679 - 686   1991年7月

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    記述言語:英語   出版者・発行元:UNIV CHICAGO PRESS  

    We have carried out new, first-principles Monte Carlo calculations of the directionally averaged, effective shear moduli of both perfect and imperfect bcc crystalline Coulomb solids for conditions appropriate to the crusts of neutron stars. The differences between the perfect and imperfect crystalline states are comparable to the residual errors in the Monte Carlo calculations, except very near the freezing point of the crust. Both values differ substantially from the values previously used for the crusts, however. To illustrate one effect of the new shear modulus calculations, we have recomputed the nonradial oscillation modes of a particular model neutron star. The results can be summarized as follows: (1) The periods of the two interfacial (i1 and i2) modes are increased by about 10% compared to the previous results. (2) the s-mode periods are increased by about 30%. (3) The periods of the f- and p-modes are hardly affected at all, as expected, since these modes are not greatly influenced by the properties of the crust. (4) The periods of the surface g-modes also are not greatly affected, because they are primarily confined to the surface fluid "ocean" layer and so are not much influenced by crustal properties. (5) The toroidal t-mode periods are increased by some 20% to 25%, also as expected. These modes, together with the spheroidal s- and interfacial i-modes, are the most sensitive to the crustal properties.

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  • NUCLEAR-REACTION RATES IN DENSE CARBON-OXYGEN MIXTURES

    S OGATA, H IYETOMI, S ICHIMARU

    ASTROPHYSICAL JOURNAL372 ( 1 ) 259 - 266   1991年5月

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    記述言語:英語   出版者・発行元:UNIV CHICAGO PRESS  

    New, first principles calculations of nuclear reaction rates in dense carbon-oxygen mixtures appropriate to Type I supernova progenitors are presented for both fluid and bcc crystalline-solid phases, based on accurate Monte Carlo evaluations of the screening potentials and a correct treatment of the quantum-statistical effects. A blocking effect of oxygen is discovered in the pycnonuclear reaction of carbon. The results are compared with the existing theories in the limit of one-component plasma cases, both for the screening potentials and for the reaction rates. Examples of the carbon ignition curve are shown.

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  • Integral-equation approach to medium-range order in molten and glassy chalcogenides(共著)

    Phys. Rev. B43 ( 2 ) 1726 - 1734   1991年

  • INFLUENCE OF ATTRACTIVE INTERACTION BETWEEN DEUTERONS IN PD ON NUCLEAR-FUSION

    T TAJIMA, H IYETOMI, S ICHIMARU

    JOURNAL OF FUSION ENERGY9 ( 4 ) 437 - 440   1990年12月

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    記述言語:英語   出版者・発行元:PLENUM PUBL CORP  

    It is shown that in a heavily deuterated palladium metal a pair of deuterons exhibits attractive interaction at short distances (almost-equal-to 0.1-0.7 angstrom) due to strong Coulomb correlations in the ion-sphere model and due to the screening action of localized 4d electrons. This mechanism can lead to enhanced thermonuclear reactions at room temperatures some 50 orders of magnitude faster than that in a D2 molecule. Characteristic signatures of predicted nuclear reactions are described.

    DOI: 10.1007/BF01588275

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  • MOLECULAR-DYNAMICS STUDY OF THE STRUCTURE AND DYNAMICS OF NETWORK GLASSES

    P VASHISHTA, RK KALIA, GA ANTONIO, JP RINO, H IYETOMI, EBBSJO, I

    SOLID STATE IONICS40-1 ( 41/ ) 175 - 179   1990年8月

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    記述言語:英語   出版者・発行元:ELSEVIER SCIENCE BV  

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  • Statistical-Mechanical Theory of Cold Nuclear Fusion in Metal Hydrides

    Setsuo Ichimaru, Aiichiro Nakano, Shuji Ogata, Shigenori Tanaka, Hiroshi Iyetomi, Toshiki Tajima

    Journal of the Physical Society of Japan59 ( 4 ) 1333 - 1340   1990年

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    記述言語:英語  

    Screening action of the s-d hybridized electrons in PdHx and TiHx is analyzed in the Fermi-Thomas approximation. The resulting interaction between hydrogen exhibits an attractive part arising from interference between the H-induced s-electrons and the valence electrons. The screening potentials due to many-body effects between the electron-screened protons are examined through solution to the hypernetted-chain equations. The nuclear reaction rates between hydrogen isotopes are calculated at various temperatures by taking account of statistical-mechanical enhancement arising from the increment in the Coulombic chemical potential of a reacting pair before and after nuclear reaction. Remarkable isotopic and temperature-dependent effects are predicted. © 1990, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.

    DOI: 10.1143/JPSJ.59.1333

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  • STATISTICAL-MECHANICAL EFFECTS ON COLD NUCLEAR-FUSION IN METAL-HYDRIDES

    S ICHIMARU, S OGATA, A NAKANO, H IYETOMI, T TAJIMA

    STRONGLY COUPLED PLASMA PHYSICS /   653 - 656   1990年

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    記述言語:英語   出版者・発行元:ELSEVIER SCIENCE PUBL B V  

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  • THERMODYNAMIC FUNCTIONS, FREEZING TRANSITION, AND PHASE-DIAGRAM OF DENSE CARBON-OXYGEN MIXTURES IN WHITE-DWARFS

    H IYETOMI, S OGATA, S ICHIMARU

    PHYSICAL REVIEW B40 ( 1 ) 309 - 315   1989年7月

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    記述言語:英語   出版者・発行元:AMERICAN PHYSICAL SOC  

    DOI: 10.1103/PhysRevB.40.309

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  • GENERALIZATION OF THE DENSITY-FUNCTIONAL THEORY WITH APPLICATION TO 3-BODY INTERACTIONS IN CLASSICAL FLUIDS

    H IYETOMI, P VASHISHTA

    PHYSICAL REVIEW A40 ( 1 ) 305 - 310   1989年7月

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    記述言語:英語   出版者・発行元:AMER PHYSICAL SOC  

    DOI: 10.1103/PhysRevA.40.305

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  • GENERALIZATION OF THE DENSITY-FUNCTIONAL THEORY AND 3-BODY INTERACTIONS IN CLASSICAL FLUIDS

    H IYETOMI, P VASHISHTA

    JOURNAL OF PHYSICS-CONDENSED MATTER1 ( 10 ) 1899 - 1904   1989年3月

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    記述言語:英語   掲載種別:速報,短報,研究ノート等(学術雑誌)   出版者・発行元:IOP PUBLISHING LTD  

    DOI: 10.1088/0953-8984/1/10/013

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  • INTEGRAL-EQUATION THEORY OF THE ORIGIN OF MEDIUM-RANGE ORDER IN MOLTEN AND VITREOUS CHALCOGENIDES

    H IYETOMI, P VASHISHTA, RK KALIA

    JOURNAL OF PHYSICS-CONDENSED MATTER1 ( 11 ) 2103 - 2107   1989年3月

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    記述言語:英語   掲載種別:速報,短報,研究ノート等(学術雑誌)   出版者・発行元:IOP PUBLISHING LTD  

    DOI: 10.1088/0953-8984/1/11/018

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  • THE INTERMEDIATE-RANGE ORDER IN MOLTEN AND GLASSY GESE2

    H IYETOMI, P VASHISHTA, RK KALIA

    SOLID STATE IONICS32-3 ( Pt.2 ) 954 - 958   1989年2月

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    記述言語:英語   出版者・発行元:ELSEVIER SCIENCE BV  

    DOI: 10.1016/0167-2738(89)90382-2

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  • Density-functional theory of three-body interactions in liquids and glasses(共著)

    Solid State Ionics32-33   954 - 958   1989年

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  • HNC THEORY OF MEDIUM-RANGE ORDER IN GLASSES

    H IYETOMI, P VASHISHTA, RK KALIA

    JOURNAL OF NON-CRYSTALLINE SOLIDS106 ( 1-3 ) 321 - 324   1988年12月

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    記述言語:英語   出版者・発行元:ELSEVIER SCIENCE BV  

    DOI: 10.1016/0022-3093(88)90283-9

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  • FREEZING TRANSITION AND PHASE-DIAGRAM OF DENSE CARBON-OXYGEN MIXTURES IN WHITE-DWARFS

    S ICHIMARU, H IYETOMI, S OGATA

    ASTROPHYSICAL JOURNAL334 ( 1 ) L17 - L20   1988年11月

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    記述言語:英語   出版者・発行元:UNIV CHICAGO PRESS  

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  • NONLINEAR DENSITY-FUNCTIONAL APPROACH TO THE CRYSTALLIZATION OF THE CLASSICAL ONE-COMPONENT PLASMA

    H IYETOMI, S ICHIMARU

    PHYSICAL REVIEW B38 ( 10 ) 6761 - 6765   1988年10月

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    記述言語:英語   出版者・発行元:AMERICAN PHYSICAL SOC  

    DOI: 10.1103/PhysRevB.38.6761

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  • THE INTERMEDIATE-RANGE ORDER AND PHASE-SEPARATION IN GLASSES

    H IYETOMI, P VASHISHTA, RK KALIA

    SOLID STATE IONICS26 ( 2 ) 161 - 161   1988年2月

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    記述言語:英語   掲載種別:研究発表ペーパー・要旨(国際会議)   出版者・発行元:ELSEVIER SCIENCE BV  

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  • 3-BODY COVALENT INTERACTIONS IN LIQUIDS AND GLASSES

    H IYETOMI, P VASHISHTA

    SOLID STATE IONICS26 ( 2 ) 161 - 161   1988年2月

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    記述言語:英語   掲載種別:研究発表ペーパー・要旨(国際会議)   出版者・発行元:ELSEVIER SCIENCE BV  

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  • STATISTICAL PHYSICS OF DENSE-PLASMAS - THERMODYNAMICS, TRANSPORT-COEFFICIENTS AND DYNAMIC CORRELATIONS

    S ICHIMARU, H IYETOMI, S TANAKA

    PHYSICS REPORTS-REVIEW SECTION OF PHYSICS LETTERS149 ( 2-3 ) 91 - 205   1987年5月

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    記述言語:英語   掲載種別:書評論文,書評,文献紹介等   出版者・発行元:ELSEVIER SCIENCE BV  

    DOI: 10.1016/0370-1573(87)90125-6

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  • FREE-ENERGIES OF ELECTRON-SCREENED ION PLASMAS IN THE HYPERNETTED-CHAIN APPROXIMATION

    H IYETOMI, S ICHIMARU

    PHYSICAL REVIEW A34 ( 1 ) 433 - 439   1986年7月

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    記述言語:英語   出版者・発行元:AMER PHYSICAL SOC  

    DOI: 10.1103/PhysRevA.34.433

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  • 宇宙物理と強結合プラズマ(共著)

    家富 洋, 伊藤 直紀, 一丸 節夫

    日本物理学会誌41 ( 10 ) 802 - 812   1986年

  • Miscibility of ionized iron atoms in hydrogen plasmas under the solar interior conditions

    Hiroshi Iyetomi, Setsuo Ichimaru

    Physical Review A34 ( 4 ) 3203 - 3209   1986年

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    記述言語:英語  

    The generalized hypernetted-chain free-energy formulas derived earlier are used for an accurate analysis of the phase properties in the binary ionic mixtures with dielectric screening of the electrons. The miscibility of iron atoms in the hydrogenic solar plasmas has been treated as a specific example. It is found that while the extent of the electronic screening effect is substantial, the resulting change in the phase diagram is not sufficiently large as to be able to account for the solar-neutrino problem. © 1986 The American Physical Society.

    DOI: 10.1103/PhysRevA.34.3203

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  • Strongly coupled plasmas in astrophysics(共著)

      41 ( 10 ) 802 - 812   1986年

  • HYPERNETTED CHAIN APPROXIMATION, CONVOLUTION APPROXIMATION AND PERFECT SCREENING IN COULOMBIC MANY-PARTICLE SYSTEM

    H IYETOMI

    PROGRESS OF THEORETICAL PHYSICS71 ( 3 ) 427 - 437   1984年

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    記述言語:英語   出版者・発行元:PROGRESS THEORETICAL PHYSICS PUBLICATION OFFICE  

    DOI: 10.1143/PTP.71.427

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  • Screening potential and enhancement of the thermonuclear reaction rate in dense plasmas

    Setsuo Ichimaru, Shigenori Tanaka, Hiroshi Iyetomi

    Physical Review A29 ( 4 ) 2033 - 2035   1984年

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    記述言語:英語  

    We present the first quantitative study of the screening potential and the effective cross section for thermonuclear reaction in dense plasmas relevant to the inertially confined fusion experiments and the interior of main-sequence stars. It is shown that the enhancement of the thermonuclear reaction rate due to strong Coulomb correlations has a considerable effect in such a dense plasma. © 1984 The American Physical Society.

    DOI: 10.1103/PhysRevA.29.2033

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  • Multiparticle Correlations in High-Density Plasmas : Improvement on the Hypernetted Chain Approximation

        1984年

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  • AMORPHOUS GLASSY PLASMA IN DENSE STELLAR MATTER

    S ICHIMARU, H IYETOMI, S MITAKE, N ITOH

    ASTROPHYSICAL JOURNAL265 ( 2 ) L83 - L86   1983年

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    記述言語:英語   出版者・発行元:IOP PUBLISHING LTD  

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  • ELECTRICAL AND THERMAL-CONDUCTIVITIES OF DENSE MATTER IN THE LIQUID-METAL PHASE .1. HIGH-TEMPERATURE RESULTS

    N ITOH, S MITAKE, H IYETOMI, S ICHIMARU

    ASTROPHYSICAL JOURNAL273 ( 2 ) 774 - 782   1983年

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    記述言語:英語   出版者・発行元:UNIV CHICAGO PRESS  

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  • SCREENING EFFECT OF DEGENERATE ELECTRON BACKGROUND IN HIGH-DENSITY PLASMAS .3. LOCAL FIELD CORRECTION DUE TO ELECTRON INTERACTION

    S ICHIMARU, H IYETOMI

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN52 ( 5 ) 1730 - 1733   1983年

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    記述言語:英語   出版者・発行元:PHYSICAL SOCIETY JAPAN  

    DOI: 10.1143/JPSJ.52.1730

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  • Density-functional theory of correlations in dense plasmas: Improvement on the hypernetted-chain scheme

    Hiroshi Iyetomi, Setsuo Ichimaru

    Physical Review A27 ( 6 ) 3241 - 3250   1983年

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    記述言語:英語  

    Multiparticle correlations in dense plasmas are analyzed in terms of the density-functional formalism
    theoretical schemes of improvement over the hypernetted-chain (HNC) approximation are thereby advanced. The proposed schemes contain no adjustable parameters
    the computational difficulties associated with these schemes are no greater than those involved in the solution of the ordinary HNC equations. The validity and accuracy of those improved HNC schemes are examined through numerical comparison with the exact Monte Carlo (MC) simulation data
    significant improvement over the HNC scheme and close agreement with the MC results are thereby demonstrated. © 1983 The American Physical Society.

    DOI: 10.1103/PhysRevA.27.3241

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  • POSSIBILITY OF AN AMORPHOUS GLASSY STATE IN A SUPERCOOLED PLASMA

    H IYETOMI, S ICHIMARU

    PHYSICAL REVIEW A27 ( 3 ) 1734 - 1736   1983年

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    記述言語:英語   掲載種別:記事・総説・解説・論説等(学術雑誌)   出版者・発行元:AMERICAN PHYSICAL SOC  

    DOI: 10.1103/PhysRevA.27.1734

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  • POSSIBILITY OF AMORPHOUS GLASSY STATE IN ASTROPHYSICAL DENSE-PLASMAS

    S ICHIMARU, H IYETOMI

    PHYSICA SCRIPTAT2 ( 2 ) 560 - 561   1982年

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    記述言語:英語   出版者・発行元:IOP PUBLISHING LTD  

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  • IMPROVEMENT ON THE HYPERNETTED-CHAIN EQUATIONS FOR DENSE-PLASMAS

    H IYETOMI, S ICHIMARU

    PHYSICAL REVIEW A25 ( 4 ) 2434 - 2436   1982年

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    記述言語:英語   出版者・発行元:AMER PHYSICAL SOC  

    DOI: 10.1103/PhysRevA.25.2434

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  • FERRELL CRITERION ON THE CORRELATION-ENERGY OF THE ELECTRON-GAS - GENERALIZATION AND CONTRIBUTIONS OF THE EXCHANGE AND CORRELATION TERMS

    S ICHIMARU, H IYETOMI, K UTSUMI

    PHYSICAL REVIEW B25 ( 2 ) 1374 - 1376   1982年

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    記述言語:英語   掲載種別:記事・総説・解説・論説等(学術雑誌)   出版者・発行元:AMERICAN PHYSICAL SOC  

    DOI: 10.1103/PhysRevB.25.1374

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  • SCREENING EFFECT OF DEGENERATE ELECTRON BACKGROUND IN HIGH-DENSITY PLASMAS .1. THERMODYNAMIC PROPERTIES

    H IYETOMI, K UTSUMI, S ICHIMARU

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN50 ( 11 ) 3769 - 3777   1981年

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    記述言語:英語   出版者・発行元:PHYSICAL SOCIETY JAPAN  

    DOI: 10.1143/JPSJ.50.3769

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  • Dielectric formulation of strongly coupled electron liquids at metallic densities. V. Possibility of a charge-density-wave instability

    Hiroshi Iyetomi, Kenichi Utsumi, Setsuo Ichimaru

    Physical Review B24 ( 6 ) 3226 - 3230   1981年

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    記述言語:英語  

    We investigate numerically the possibility of the soft-mode charge-density-wave (CDW) instability in a degenerate electron liquid with a rigid positive-charge background, on the basis of the dielectric formulation developed in previous papers. The estimated values for the critical density and the wave number for the onset of such an instability are rs85 and qc1.875qF. A physical account is given on the interrelationship between the Wigner transition, the violation of the Ferrell condition, and the CDW instability. It is shown through a numerical example that the "local approximation" for exchange and correlation can lead to manifestly inaccurate predictions on the onset of the CDW instability. © 1981 The American Physical Society.

    DOI: 10.1103/PhysRevB.24.3226

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  • SCREENING EFFECT OF DEGENERATE ELECTRON BACKGROUND IN HIGH-DENSITY PLASMAS .2. ELECTRIC RESISTIVITY

    H IYETOMI, K UTSUMI, S ICHIMARU

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN50 ( 11 ) 3778 - 3781   1981年

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    記述言語:英語   出版者・発行元:PHYSICAL SOCIETY JAPAN  

    DOI: 10.1143/JPSJ.50.3778

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▶ 全件表示

Works(作品等)

  • 経営リスク評価の新しいフレームワーク探索

    2004年
    -
    2005年

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  • Quest for a New Framework to Evaluate Management Risk

    2004年

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共同研究・競争的資金等の研究

  • 外生的ショックに対する大規模経済ネットワークの応答ダイナミクスの解明とその応用

    研究課題/領域番号:20H02391  2020年04月 - 2023年03月

    日本学術振興会  科学研究費助成事業 基盤研究(B)  基盤研究(B)

    藤原 義久, 家富 洋, 吉川 洋, 相馬 亘, 井上 寛康, 後藤 弘光

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    配分額:16380000円 ( 直接経費:12600000円 、 間接経費:3780000円 )

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  • 有向ネットワークにおける流れ構造の階層性と循環性

    研究課題/領域番号:18K03451  2018年04月 - 2021年03月

    日本学術振興会  科学研究費助成事業 基盤研究(C)  基盤研究(C)

    家富 洋

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    配分額:4420000円 ( 直接経費:3400000円 、 間接経費:1020000円 )

    ノードとそれらをつなぐ向き付きのリンクから構成されネットワーク上には,様々な流れ構造が存在する。本研究の目的は,そのような有向ネットワーク上の流れ構造を,特に階層性と循環性に注目し,解析に必要な手法を開発するとともに,得られた解析手法をいくつかの応用上も重要な現実の有向ネットワーク系へ適用することである。
    解析手法の開発面においては,ヘルムホルツ・ホッジ分解,コミュニティ抽出,蝶ネクタイ構造分解,バネ電気モデルによる可視化などを組み込んだ統合的解析ツール(FALCON)の開発を開始し,すでにそのプロトタイプを作成し,GitHub上で公開した。ヘルムホルツ・ホッジ分解は,有向ネットワーク上での流れ構造を勾配流成分とループ流成分へユニークに分割する。
    具体的な解析対象として,企業間取引関係,貿易収支関係および株所有関係を取り上げた。それぞれのネットワークについては,我が国の約100万社間の約500万取引を含む東京商工リサーチ社のデータ(2016年収集),IMFにより公開されているDOTS(Direction of Trade Statistics)データベース,東洋経済新報社によって収集された国内上場企業に対する大株主情報データベース(最大で上位30位まで)から構築した。企業取引ネットワークにおける取引流の循環成分に着目すると,より明瞭に産業コミュニティを抽出できることを明らかにした。また,2国間の貿易は大きく不均衡であっても,貿易収支を多角的な視点で捉えれば(第3国を通じての間接的な貿易関係を考慮),両国は貿易によって互恵関係を持ち得ることを指摘した。株所有ネットワークについては,まず蝶ネクタイ構造(入力成分,強連結成分,出力成分)に分解し,さらに強連結成分に対してヘルムホルツ・ホッジ分解を適用することにより,複雑な株式持合い関係を紐解いた。

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  • ビッグデータを駆使したグローバル社会の階層構造の解明

    研究課題/領域番号:17KT0034  2017年07月 - 2020年03月

    日本学術振興会  科学研究費助成事業 基盤研究(B)  基盤研究(B)

    池田 裕一, 家富 洋, 水野 貴之

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    配分額:18590000円 ( 直接経費:14300000円 、 間接経費:4290000円 )

    本研究では,グローバル化の階層構造をビッグデータとネットワーク科学の手法で見える化し,ヒト・モノ・カネのグローバルな流れに潜むコミュニティの孤立性を表す指標を開発する。そのために,自由貿易を前提とした経済共同体構想を阻害する「コミュニティの孤立化」によりもたらされる「コミュニティ間格差」の実態を解明する。
    (1)カネとモノについての世界データベースの完成:
    (a) 企業間の国際株式所有データ,(b) 企業間の国際製品サービス取引データ,(c) (a)のOwnerIDと(b)の企業IDの紐づけデータ,(d) 世界の上場企業の株価と出来高の日次推移データ,(e) 取引情報と株価を取得した企業の損益計算書のデータ,(f) 取引情報と株価を取得した企業の貸借対照表のデータ,(g) (b)の各企業の株主リスト(企業ID、企業名、持ち分比率),(h) (b)の各企業の株式保有リスト(企業ID、企業名、持ち分比率)
    (2)モノの流れの解析:S&Pデータを用いて,全世界約60万社からなる国際製品サービス取引ネットワークについてコミュニティ解析を行うとともに,モノの流れにおける流れ成分と回転成分の同定を行った。これらの成分の特徴に基づいて,経済成長との対応関係を検討中である。
    (3)カネの流れの解析:国際株式所有ネットワークにおいて国際租税回避の拠点となる国と企業を同定するための中心性指標の定式化とアルゴリズムを提案した。この新しい中心性指標を用いて,Fortune500の多国籍企業グループの国際租税回避の特徴を抽出した。
    (4)ヒトの流れの解析:苗字・国籍ビッグデータによる民族の空間的特徴の抽出と,人流ビッグデータによる民族のセグリゲーションの解析を行った。また,生産要素としてのヒトの移動については,途上国からの移民の移民先の国での同化について公表データを用いた解析を行った。

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  • 大規模な経済ネットワークシミュレーションに基づく経済システムの脆弱性のモデル化

    研究課題/領域番号:17H02041  2017年04月 - 2020年03月

    日本学術振興会  科学研究費助成事業 基盤研究(B)  基盤研究(B)

    藤原 義久, 荒田 禎之, 相馬 亘, 井上 寛康, 池田 裕一, 青山 秀明, 家富 洋

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    配分額:17550000円 ( 直接経費:13500000円 、 間接経費:4050000円 )

    実体経済の要となる金融機関・企業間の信用ネットワークと企業間の生産ネットワークを対象として、ネットワーク科学の手法と京コンピュータを含む大規模な計算機資源を活用し、巨大な経済ネットワークの実データの構造とそのダイナミクス、リスクやストレスの連鎖現象、経済ネットワーク自身の時間的な発展などを明らかにすることを目的とする。前年度までの研究成果として、物価・実体経済ネットワーク・脆弱性にかかるシミュレーションのモデル化を行った。今年度はそれらモデル化を実装、拡張しながら、以下の応用展開を行った。
    1. 【連鎖倒産やサプライチェーン上でのストレス伝播モデルとシミュレーション】システムの一部に生じた経済ストレスや破綻が経済ネットワーク上でどのように波及するか、そのモデル化を点過程(point process)を用いて行った。また、大きな自然災害で典型的にみられるような生産ネットワークにおける供給停止が及ぼす影響のシミュレーションを理化学研究所の京コンピュータを含むスパコン上に実装して、そのモンテカルロシミュレーションを多数のシナリオについて行った。
    2. 【経済ネットワークの構造・ダイナミクスのモデル化とシミュレーション】経済ネットワークの構造やそのダイナミクスを記述するための確率モデルとして、Exponential Random Graph Model (ERGM), SAOM (stochastic actor-oriented model)などのモデル構築を行って、マルコフ連鎖モンテカルロ(MCMC)などの手法でパラメータを推定する手法を開発した。
    3. 【可視化ツールの開発】東日本大震災による生産活動の停止が及ぼす国内約百万社への影響を可視化するツールを開発してその公開の準備を進めた。

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  • 多者間ネッティングの数理的基盤の構築とその応用

    研究課題/領域番号:16K13375  2016年04月 - 2018年03月

    日本学術振興会  科学研究費助成事業 挑戦的萌芽研究  挑戦的萌芽研究

    家富 洋, 渡辺 努, 飯野 隆史, 吉川 悠一

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    配分額:2730000円 ( 直接経費:2100000円 、 間接経費:630000円 )

    システミック・リスクを緩和するにあたり,多者間ネッティングは重要である。本研究では,変分原理によって多者間ネッティングの解を一意的に決定する方式を考案した。加えて,得られた多者間ネッティング理論を貿易収支ネットワークと企業間取引ネットワークにおける階層・循環構造の解明に応用した。

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  • ビッグデータ先導型紛争研究:紛争の潜在的加害者の見える化

    研究課題/領域番号:15KT0052  2015年07月 - 2019年03月

    日本学術振興会  科学研究費助成事業 基盤研究(B)  基盤研究(B)

    水野 貴之, 大西 立顕, 家富 洋, 渡辺 努, 久野 遼平, 中渡瀬 秀一, 土井 翔平, 新井 優太, 伊藤 亮人, 小髙 充弘, 南 玲子

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    配分額:18070000円 ( 直接経費:13900000円 、 間接経費:4170000円 )

    グローバルな企業間ネットワークの構造を調査したのち,企業間のグローバルな繋がりが「紛争鉱物」等の世界的な拡散に与える影響について議論した.複数の企業が国境を越えて同じ産業内でコミュニティを形成していることを突き止め,コミュニティ間を繋ぐ少数の企業の存在が,世界中の企業間を平均6取引で繋げていることを明らかにした.このような企業間の繋がりの特徴は,紛争鉱物や奴隷労働問題などのリスク対策に利用することができる.単純な拡散モデルとコミュニティ構造に関する特徴から,G8各国の特定の産業に属する僅かな企業に対する紛争鉱物の購入規制が,紛争鉱物の世界的な使用を実質的に減少させることを数値的に示した.

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  • 持続的・安定的な成長のためのグローバル社会の相互依存関係性の解明

    研究課題/領域番号:26350422  2014年04月 - 2018年03月

    日本学術振興会  科学研究費助成事業 基盤研究(C)  基盤研究(C)

    池田 裕一, 吉川 洋, 渡辺 努, 青山 秀明, 家富 洋, 水野 貴之, 大西 立顕

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    配分額:4160000円 ( 直接経費:3200000円 、 間接経費:960000円 )

    近年,貿易額は年々増加の一途をたどっており,あらゆる国の産業の間にリンクが張られ世界経済全体が大きいネットワークとなっている。今後,新しい経済共同体が形成され,国際貿易は更に盛んになるであろう。このような経済のグローバル化にともない,あらゆる国の産業の間に働く相互作用は強くなる。
    本研究では,データ科学,ネットワーク科学,計算科学などの方法論を駆使して,グローバル社会の相互依存関係性を明らかにする。この研究によって,危機時におけるコミュニティの構造変化,景気循環の同期現象など,が明らかになった。また,特定の国で発生した経済危機が他の国々へ広がっていくグローバル経済危機の現象をモデル化できた。

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  • 複雑系ネットワークのアプローチによる社会システムのクライシスに関する研究

    研究課題/領域番号:25282094  2013年04月 - 2017年03月

    日本学術振興会  科学研究費助成事業 基盤研究(B)  基盤研究(B)

    藤原 義久, 木村 真, 中村 知道, 島 伸一郎, 青山 秀明, 眞鍋 雅史, 佐藤 哲也, 家富 洋, 池田 裕一, 相馬 亘, 吉川 洋

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    配分額:15860000円 ( 直接経費:12200000円 、 間接経費:3660000円 )

    マクロ経済における景気循環、物価変動、経済危機などの理解は未解決の重要な社会的な課題である。数百万の企業・金融機関とその間の関係性ネットワークを含む大規模な実データに基づき、経済ネットワーク上での経済変動の同期や伝播の現象のモデル化・シミュレーションを行い、物価変動の伝播、経済的なストレス波及のダイナミクスなどを解明した。また、世界で初めて京コンピュータを大規模な経済シミュレーションに応用することに成功した。

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  • 複雑系の動的相関構造:ランダム行列理論とヒルベルト変換の融合

    研究課題/領域番号:25400393  2013年04月 - 2016年03月

    日本学術振興会  科学研究費助成事業 基盤研究(C)  基盤研究(C)

    家富 洋, 相馬 亘

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    配分額:4680000円 ( 直接経費:3600000円 、 間接経費:1080000円 )

    複素ヒルベルト主成分分析(CHPCA)とランダム行列理論(RMT)を組み合わせ,複雑多変量系におけるリード・ラグ関係などの動的相関を効果的に検出できる新手法を開発した。RMTは統計的に有意味な主成分を抽出するための明確な判定規準を与える。加えて,時系列が自己相関を含む場合にも有効な帰無仮説を提供するランダム回転シャッフリング法も開発した。先行,一致,遅行の特性をもつことが確立されている景気動向基礎指標データ群に新手法を適用し,その有効性を確認した。また,得られた手法に用いて,株式市場における動的相関構造,個別価格の集団運動,国際的な金融ネットワークにおける同期コミュニティなどを明らかにした。

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  • マクロ・エコノフィジックス

    研究課題/領域番号:24243027  2012年10月 - 2015年03月

    日本学術振興会  科学研究費助成事業 基盤研究(A)  基盤研究(A)

    吉川 洋, 青山 秀明, 家富 洋, 相馬 亘, 藤原 義久, 渡辺 努, 池田 裕一

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    配分額:26130000円 ( 直接経費:20100000円 、 間接経費:6030000円 )

    現在の主流派経済学はミクロの経済主体の最適化行動の相似拡大としてマクロ経済の動きを捉えようとする。本研究は,現実のマクロ経済現象を直視し,多数の相互作用する経済主体のマクロな振舞いは代表的な経済主体のものとは異なりうることを前提として統計物理学的なアプローチによるマクロ経済学の再構築を行う。具体的な研究対象は,1)労働生産性分布の実証解析とモデル化, 2)中小企業の労働生産性と技術革新,3)物価指数とデフレ/インフレとの動態関係などである。

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  • 大規模経済ネットワークの構造とダイナミクス

    研究課題/領域番号:22300080  2010年 - 2012年

    日本学術振興会  科学研究費助成事業 基盤研究(B)  基盤研究(B)

    家富 洋, 青山 秀明, 相馬 亘, 藤原 義久, 池田 裕一, 池田 裕一

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    配分額:11310000円 ( 直接経費:8700000円 、 間接経費:2610000円 )

    ノード数が百万個程度の大規模複雑ネットワークに対してもその構造とダイナミクスを解析できる手法(コミュニティ抽出、可視化)を開発した。得られた手法の応用として、経済系ネットワーク(企業間取引によって形成された生産ネットワーク、銀行・企業間貸借関係に基づく信用ネットワーク、株価間の相関ネットワークなど)の解析を行った。このような経済現象を実証的に明らかにする試みから、いくつかの新しい知見を得た。

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  • 多重ネットワーク分析手法を用いた新たな経済指標の検討

    研究課題/領域番号:20330060  2008年 - 2010年

    日本学術振興会  科学研究費助成事業 基盤研究(B)  基盤研究(B)

    玉田 俊平太, 相馬 亘, 藤原 義久, 青山 英明, 家富 洋, 井上 寛康, 藤田 昌久

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    配分額:18330000円 ( 直接経費:14100000円 、 間接経費:4230000円 )

    本研究では、企業間の取引(ニーズ)と特許の発生(シーズ)に着目し、現在の日本の企業間イノベーションシステムがどのように構築されているかを分析した。データとして100万の企業をノードとし、それらにおける取引と特許の共同出願によるリンクからなる多重ネットワークを分析した。分析に、産業連関表、ERGモデル、ベイジアンネットワークの3つを用いた。産業連関表の分析から、取引金額よりも取引件数の方が共同出願により影響を与えているであろうことが推測された。続いてERGモデルに基づく分析から、企業間の取引は双方向になり、取引と特許の共同出願は同時に発生しやすいことがわかった。またこれより複雑な関係はあまり有意に発生しないこともわかった。最後にベイジアンネットワークに基づく分析から、企業間の取引関係が判明すれば、特許の共同出願と産業の種類は独立になることがわかった。

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  • 電荷揺らぎに由来する強相関量子相の研究

    研究課題/領域番号:18002008  2006年 - 2010年

    日本学術振興会  科学研究費助成事業 特別推進研究  特別推進研究

    後藤 輝孝, 根本 祐一, 北澤 英明, 鈴木 博之, 金田 寛, 柳澤 達也, 家富 洋, 大野 義章, 武田 直也, 鶴田 健二, 酒井 治, 赤津 光洋, 石井 勲, 三本 啓輔

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    配分額:284440000円 ( 直接経費:218800000円 、 間接経費:65640000円 )

    超音波歪みは明確な対称性を備え、電子やイオンの量子系が持つ電気四極子と結合するので、超音波計測による弾性定数や吸収係数の測定により、四極子感受率を観測できる。本研究では、低温での高分解超音波位相差計測を駆使し、希土類化合物の局在4f電子の非クラマース2重項,カゴ状化合物の局所振動のラットリング,ボロン添加シリコン結晶中の原子空孔軌道などに現れる「電荷揺らぎに由来する強相関量子相」を研究した。

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  • ソフト凝集物質における長距離電子相関と構造に関する理論的研究

    研究課題/領域番号:16540301  2004年 - 2006年

    日本学術振興会  科学研究費助成事業 基盤研究(C)  基盤研究(C)

    長谷川 正之, 西舘 数芽, 家富 洋

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    配分額:2200000円 ( 直接経費:2200000円 )

    グラファイト及びグラファイト系ナノ構造物質の構造とダイナミックスにおける長距離電子相関効果を明らかにするために、半経験的な計算理論を展開した。近年、このような物質に対しても密度汎関数理論に基づく計算が数多く行われたが、最も基本的なグラファイトの層間凝集エネルギーの定量的評価でも限界を露呈している。このような計算では、長距離電子相関に由来するファン・デル・ワールス相互作用が無視されていて、近距離における電子相関効果も適切に考慮されていないことがその原因である。本研究では、この困難の克服を目指して、第一原理計算を経験的なファン・デル・ワールス相互作用で補強するという半経験的な計算理論の再構築を図り、グラファイトに応用することによって理論の妥当性を確認した。また、この理論を拡張することによって、孤立した単層カーボンナノチューブの変形エネルギーに関する計算理論を構築して、圧力下における動径方向の変形に応用した。その予測は実験的に得られる結果と整合していて、計算理論の有効性が明らかになった。更に、この理論を応用してナノチューブの変形に伴う電子構造変化を調べ、半導体-絶縁体転移を引き起こす圧力を推定した。この結果は、カーボンナノチューブの形態と電子物性の関係を明らかにするための出発点となり、実用的有用性も期待される。
    関連研究として、カーボンナノチューブの構造欠陥とリチュームイオン吸着との関係を第一原理計算分子動力学の手法を用いてシミュレートすることにより、カーボンナノチューブをリチューム二次電池の電極として利用できる条件を検討した。また、半導体CdSにおける種々の欠陥生成・不純物添加に伴う電子構造変化について系統的な計算を行い、実用的に重要なP-ドーピングの可能性を模索した。

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  • 経済・社会現象への物理学的アプローチ

    2004年

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    資金種別:競争的資金

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  • クーロン固体の固溶特性を利用した新しい多価イオン冷却法の探求

    研究課題/領域番号:14658129  2002年 - 2003年

    日本学術振興会  科学研究費助成事業 萌芽研究  萌芽研究

    家富 洋

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    配分額:1500000円 ( 直接経費:1500000円 )

    クーロン相互作用でイオンが強く結合したプラズマは白色矮星などの高密度星内部で,実験室系ではレーザー冷却されたイオントラップ系で実現されている.本研究によって得られた,2種のイオンが負電荷一様背景中で不規則に固溶した固体(クーロン固溶体)の相分離に対する安定性およびその弾性的性質についての詳しい解析結果が公刊された.今年度混合安定性についての解析をさらに進め,電荷比が約6以上で大きな電荷をもったイオンの組成比0.2近傍においてもっとも混合相が安定化することを見いだした.ローレンスリバモア国立研究所ではBe^{+}とXe^{+44}とからなるイオントラップ系のレーザー冷却実験が最近行われた(L.Gruber, Phys.Rev.Lett., vol.86,pp.636-639,2001).その実験では組成比が非常に小さいXeイオンが中心部に集中し,レーザー冷却のターゲットであるBeイオンがXeイオンを取り囲むように相分離が生じた.本研究の結果に照らしてみるとXeイオンの組成比を最適値0.2に近づけることによってXeイオンに対する間接冷却の効率が格段に改善される可能性があることが分かる.今後,そのようなイオントラップ系におけるプラズマ相特性の解明とともに多価イオンを間接冷却する有効性について分子動力学シミュレーションによって定量的に検討する.付け加えて白色矮星の内部でクーロン結晶が実現されているとの観測事実がつい最近報じられた(朝日新聞,2004年2月19日).これは高齢の白色矮星の振動を詳細に分析することに拠っている.観測精度の向上とともに本研究で得られたクーロン固溶体の弾性定数についての知見が白色矮星の内部状態の解明に大いに役立つものと期待される.

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  • インターネットを利用した計算物理に関する国際共同研究の試み

    研究課題/領域番号:14658041  2002年

    日本学術振興会  科学研究費助成事業 萌芽研究  萌芽研究

    小林 迪助, 奥西 巧一, 草部 浩一, 家富 洋

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    配分額:1300000円 ( 直接経費:1300000円 )

    本研究は新潟大学理学部および大学院自然科学研究科とデルフト工科大学応用科学部(オランダ)との間の交流協定を背景にした.内容については計算物理における基本的手法から多数のコンピューターの同時利用によって大規模計算を可能にする先端的並列計算技術までカバーすることを目的とした.参加する学生は単に受動的に講義を聴講するばかりではなく,学生同士が国際的チームをつくり講義を補完する様々な演習課題を共同で遂行した.これは学生に対して課題解決能力の獲得ばかりではなく,英語を用いたコミュニケーション技術を向上させる機会を与えるためである.通常のコミュニケーションはインターネットを使って行われた.合わせて相互に訪問する機会を計画に組み入れた.まず2002年9月28日から約1週間,デルフト工科大学側から教員2名および大学院生3名が新潟を訪問し,共同講義が開始された.PCの組み立て,並列計算用PCクラスターの構築および経路積分量子モンテカルロ(PlQMC)シミュレーションの講義が実施された.10月中旬から12月初旬までPlQMCの応用として液体ヘリウム中の電子拡散の問題が演習課題として行われた.12月14日から約1週間,新潟大学側から教員1名および大学院生4名がデルフト工科大学を訪問し,密度汎関数理論に基づく第一原理電子状態計算に関する講義が行われた.訪問後,2003年3月末までシリコン中の電子状態を求めるための計算コード作成が行われた.いくつかの問題点(インターネットテレビ会議の利用がネットワークの制限で実施できなかったこと,博士論文や修士論文の研究との両立のむずかしさ,学生の英語力の不足など)が浮かび上がってきたが,このような試みが我が国における物理高等教育の改善につながるものと自負している.本共同講義の途中経過が2002年12月21日の日本物理教育学会新潟支部会で報告されたことを付記する.

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  • 並列計算グリッドを用いたハイブリッド量子/古典数値解析法の開発

    2001年 - 2004年

    JST計算科学技術活用型特定研究開発推進事業(ACT-JST) 

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    資金種別:競争的資金

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  • 並列計算手法による超イオン性の発現機構の研究―高速イオン物質開発の基礎―

    研究課題/領域番号:12440085  2000年 - 2002年

    日本学術振興会  科学研究費助成事業 基盤研究(B)  基盤研究(B)

    小林 迪助, 鶴田 健二, 草部 浩一, 家富 洋

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    配分額:8400000円 ( 直接経費:8400000円 )

    米国ルイジアナ州立大学の菊池英明研究員,海外共同研究者である中野愛一郎準教授,共同研究者の鶴田健二氏の協力により並列計算機システムテムの配備と可動チェック,並列計算手法の準備を整えた.
    つぎに貴金属ハライド,貴金属3元化合物に対してバンド計算とDV-Xα法によりこれらの物質のp-d混成状態を調べることにより超イオン性の発現機構の研究を行った.また,フッ化物超イオン導電体を層状に配置した人工の超イオン導電体を作成し,MD法によりその構造と動的性質を調べ,高イオン伝導度をもつ導電体開発の提言を行った.
    一方,二酸化チタンのナノ粒子に対する焼結過程についてMD法によるシミュレーションを実行し,ナノフェーズ相における内部構造や空間電荷分布と基本の結晶相との関係を調べた.またクーロン固溶体の力学的性質も解明した.
    さらに,開発してきた高効率のタイトバインディング分子動力学(TBMD)コードを用いて,ダイヤモンド結晶粒界の構造と水素添加効果,Si結晶とアモルファスSi中での水素原子の高温拡散経路の解析等を実施した.
    以上のように本研究計画の遂行によって,多くの成果が得られ,国内外の会議で発表されるとともに,現在もさらに進展しており,今後の発展が期待される.

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  • 変分APW法の開発と超イオン伝導物質の電子状態解析

    研究課題/領域番号:11640371  1999年 - 2001年

    日本学術振興会  科学研究費助成事業 基盤研究(C)  基盤研究(C)

    家富 洋, 長谷川 彰

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    配分額:2900000円 ( 直接経費:2900000円 )

    1)電子状態計算手法の整備・開発
    変分APW法の詳細を公刊した.また,変分APW法の基本的アイディア(マフィン・ティン球半径の変分的決定)がLMTO法やASW法に対しても適用可能であることを確認した.また,電子状態レベルでイオンのダイナミックスを記述するためにタイトバインディング(TB)法に基づく分子動力学シミュレーション法の開発を行った.MPI(Nessage Passing Interface)を利用することにより複数のコンピューターを同時に使用できる並列計算アルゴリズムを組み込み,計算を格段に高速化した.今後の課題は第一原理的な変分APW計算から如何にTBパラメターを抽出するかである.
    2)p-d状態混合強度とイオン伝導度
    一連の貴金属ハロゲン化物,AgXおよビCuX(X=C1,Br, I)、について変分APW法に基づく電子状態計算を行うことにより,p-d状態混合強度とイオン伝導度との相関を包括的に調べた.p-d状態混合強度を特徴づけるパラメター「generalized covalency」を新たに導入し,超イオン伝導性発現の基本要因として提案している「弱いp-d状態混合の実現」が普遍的に成立することを確証した.貴金属ハロゲン化物について簡便なTB法を用いた電子状態計算も行った.TBパラメターを適切に取ることにより,変分APW計算に基づいてすでに得られたp-d状態混合強度とイオン伝導度との相関関係の結果を定性的に再現できることを示した.
    3)その他の関連研究
    超イオン伝導性ガラス(Ag/Ge/Se)の構造やダイナミックスを分子動力学シミュレーションによって明らかにした.特に銀原子クラスター化の前駆現象を発見し,その詳細を明らかにした.二酸化チタン(超イオン伝導体の母物質)のナノ粒子の焼結過程を電荷可変型ポテンシャルに基づく分子動力学シュミレーションで調べ,基盤結晶構造の違い(rutile, anatase)によって焼結ナノ構造体の特性が定性的に異なることを見出した.

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  • 軌道の秩序と揺らぎによる格子異常・超音波による研究

    研究課題/領域番号:11220205  1999年 - 2001年

    日本学術振興会  科学研究費助成事業 特定領域研究(B)  特定領域研究(B)

    後藤 輝孝, 草部 浩一, 長谷川 彰, 根本 祐一, 家富 洋, DONNI Andreas

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    配分額:42700000円 ( 直接経費:42700000円 )

    本研究班は格子歪みが軌道自由度系の四重極子と結合することを積極的に利用し、超音波による軌道秩序と揺らぎの研究を行なった。
    極低温超音波計測によって、Ce_xLa_<1-x>B_6の磁気相図を確立した。x=0.75ではIV相から磁気秩序III相への転移が見られるが、x=0.70、x=0.65ではIV相がT=0Kまで安定である。弾性定数C_<44>の極低温測定によるとx=0.70、x=0.65の低温極限は一致しているが、x=0.60、x=0.50では違った極限となっている。中村らの比熱の結果と照らし合わせて、x=0.60、x=0.50では秩序相は出現せず非磁性状態となると結論した。x=0.75とx=0.70のIV相の熱膨張実験を行い、[001]方向では膨張し[111]方向では収縮することを見いだした。これはIV相で三方晶系に歪んでいることを示しており、O_<yz>=O_<zx>=O_<xy>≠0の強四重極子転移を示唆している。HoB_6の強四重極子転移でも三方晶系への歪みを観測し、Ce_xLa_<1-x>B_6のIV相の理解を大いに助けた。
    HoB_2C_2では横波超音波(C_<11>-C_<12>/2,C_<44>,C_<66>にソフト化が見られE2重項とAもしくはB1重項が偶然縮退をした3重項模型がよいことを示した。巨大磁気抵抗を示すLa_xSr_<1-x>MhO_3、Pr_xCa_<1-x>MnO_3の軌道秩序に関しても研究が進展した。これらの系では軌道秩序直上で共通して(C_<11>-C_<12>/2にソフト化が見られた。Mn^<3+>のEg軌道の四重極子O^0_2,O^2_2とのJan-Teller結合が重要であり、その大きさは10〜100Kであり、Millsの理論予想よりもはるかに小さいことがわかった。また、電荷揺らぎによるソフト化を見いだし、Pr_xCa_<1-x>MnO_3(x=0.50)の電荷秩序ではランダウ相転移に基づく解析に成功した。

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  • 電流及びスピン密度汎関数法に基づく相対論的バンド理論の構築とf電子系への適用

    研究課題/領域番号:09640424  1997年 - 2000年

    日本学術振興会  科学研究費助成事業 基盤研究(C)  基盤研究(C)

    長谷川 彰, 家富 洋

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    配分額:2900000円 ( 直接経費:2900000円 )

    従来の電子エネルギーバンド理論においては、電子の軌道運動の影響は無視されてきた。このような近似は、固体内の電子状態が自由電子に近い状態にあるときには許されるが、希土類化合物やアクチニド化合物におけるf電子のように、局在に近い状態にある電子の軌道角運動量は決して小さくはない。本研究はf電子系の電子構造に対する軌道電流の影響を調べることを目的とし、電磁場の中におかれた相互作用する電子系に対する半古典的な量子電磁力学のハミルトニアンから出発し、相対論的電流スピン密度汎関数理論を構築した。この新しい理論の枠組の中では、基底状態および基底状態エネルギーは電荷密度と磁気密度により一意的に決まる。一般化されたHohenberg-Kohn定理が成立することを示した。変分原理に基づき、これらの基本変数に関して基底状態エネルギーを最小化することにより、新しいKohn-Sham-Dirac型のセルフコンシステント一電子方程式を導いた。この一電子方程式の有効性を確かめるために、孤立した希土類3価イオンの電子状態の計算に適用した。セルフコンシステントに決められた内部磁場により、磁気方位量子数による縮退は完全に解ける。すべての占有準位について加えて得られたスピン磁気モーメントと軌道角運動量磁気モーメントはHund則をよく再現する。この結果は、Hund則にはスピン分極効果とスピン軌道相互作用が本質的に重要な役割を果たしていることを示す。定量的に言えば、軌道電流の効果はHund則にわずかな影響しか及ぼさないが、各エネルギー準位のエネルギーをかなり修正する。この結果は、重い電子系のf電子系化合物では軌道電流が電子構造に及ぼす影響は無視できないことを示している。本研究は、電子構造に対する軌道電流の影響を調べる上での出発点になるものである。

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  • 多元物質における結晶異方性および原子異種性を考慮した新しい電子状態計算手法の開発

    研究課題/領域番号:08640481  1996年 - 1997年

    日本学術振興会  科学研究費助成事業 基盤研究(C)  基盤研究(C)

    家富 洋, 長谷川 彰

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    配分額:2000000円 ( 直接経費:2000000円 )

    1.新しい電子状態計算の定式化
    密度汎関数理論におけるエネルギー変分原理を利用した「変分Augmented Plane Wave(VAPW)法」を定式化した.この新しい方法は,従来のAPW法に比べ,構成原子の非異種性や結晶異方性の取り扱いに大きな改良を与えると期待される.
    2.VAPW計算コードの開発
    バンド計算技法に関する資源を再活用しながら,VAPW計算コードを開発した.特にmuffin-fin(MT)ポテンシャルを数種のパラメターで特徴付け,変分計算の効率化を行った.
    3.VAPW法の有効性の確認
    VAPW法をアルカリ・テルル化物に適用した.MT半径を変分的に取り扱うことにより,非対称な多元物質に対する電子物性(凝集エネルギー,格子定数,体積弾性率など)の計算精度が大きく高められることを確かめた.また,共有結合のために異方的効果が大きいダイヤモンド構造をとるSiにVAPW手法を適用し,MT近似の範囲内でもセルフ・コシン,ステント計算による基底エネルギーを下げることができることを示した.
    4.超イオン導電体の電子状態
    逆蛍石構造を基盤構造としてもつ超イオン導電体,α-Ag_2Teに対してVAPW法に基づく電子状態の計算を広範囲に行い,超イオン導電性発現要因を電子論的に明らかにした.
    5.今後の課題
    (1)結晶異方性を考慮したクーロン積分の高精度計算コードの開発,(2)計算機特性(ベクトル,並列)に合わせたプログラムの高速化(特に行列対角化部分について).

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  • 高密度天体プラズマ中の相転移現象

    研究課題/領域番号:04455010  1992年 - 1994年

    日本学術振興会  科学研究費助成事業 一般研究(B)  一般研究(B)

    一丸 節夫, 尾形 修司, 家富 洋

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    配分額:3600000円 ( 直接経費:3600000円 )

    1.多種イオン高密度プラズマの状態方程式と相図
    計算機実験により多種イオンプラズマの状態方程式を定め,計算値が相図作成に必要な精度を持つことを熱力学的総和則を用いて確かめた,得られた状態方程式をもとに,様々な多種イオンプラズマの相図を作成した。また,白色矮星内部物質であるC-O-Me系へ応用した。
    2.高密度部分電離プラズマの相転移と輸送特性
    高密度部分電離物質の状態方程式を,プラズマによる原子レベル浅化/消失,中性原子間分散力の熱増大などを取り入れて求めた。第二に,その電気・熱伝導係数を,液体水素で見いだされた電子-イオン間強結合効果,中性原子による剛体球散乱,熱伝導度における比熱の効果などを取り入れて求めた。第三に,自由電子による光子吸収断面積を第一原理から定式化し,輻射輸送効率を計算した。
    3.高密度固体中冷核反応の温度効果
    高密度クーロン固体中の冷核反応は,有限温度では反応率が基底状態値より増大する。一成分系について,この増大率を最近接粒子間の波動関数の数値解より求め,その解析表式を導出した。
    4.超高圧金属中核融合
    白色矮星の超新星過程に見られる冷核反応に関する理論解析手法を,地上実験室での超高圧物質へ発展させた。超高圧金属中での核融合は有効なエネルギー解放手段となる可能性があることを,見いだした。
    5.量子クーロン固体の状態方程式と融解転移
    量子クーロン固体の有限温度における自由エネルギー値を,経路積分表示に基づく量子モンテカルロ計算により求めた。高密度星内部にみられるヘリウムおよび炭素物質に応用し,融解における量子効果,非調和振動効果を定量的に明らかにした
    6.高密度クーロン物質のクラスター集合体模型
    クーロン・クラスター(粒子数2〜60)の状態方程式・熱的構造安定性を数値実験により解析し,その知見を基にクラスターの集合体として古典一成分プラズマを記述する模型を提案した。

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  • 高密度多種イオンプラズマの相構造,電子状態および原子・分子過程

    研究課題/領域番号:01460246  1989年 - 1991年

    日本学術振興会  科学研究費助成事業 一般研究(B)  一般研究(B)

    一丸 節夫, 家富 洋

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    配分額:5200000円 ( 直接経費:5200000円 )

    1.高密度多種イオンプラズマの状態方程式と相図
    様々な電荷比,組成比をもった二種および三種イオン系の相関特性を計算機実験および積分方程式理論を用いて解析し,状態方程式,遮蔽ポテンシャル,ブリッジ関数を求めた.白色矮星の内部状態に対応したプラズマについてその相図を計算し,星の内部構造や冷却過程に対する相変化の影響を検討した.
    2.高密度水素プラズマの熱力学関数,輸送係数,不純物電子状態
    高密度水素プラズマの状態方程式,輸送係数,遮蔽関数について,電子ーイオン間強相関効果を表わす「前兆束縛状態」を物理的に明解な形で組み込んだ正確な解析表式を導出した.合わせて,強相関水素プラズマ中における不純物の電子準位や電離度についても理論的に検討した.
    3.高密度プラズマ中の核融合反応
    天体高密度プラズマ(縮退星内部・表層,太陽内部),実験室高密度プラズマ(衝撃圧縮,金属中水素,超高圧金属)中の核融合反応率を,二体過程,電子遮蔽冷核過程,多体増倍効果に分け,見通しよく評価・検討し,原著論文および総説にまとめた.
    4.中性子星外殻物質の伝導度および剛性率
    中性子星外殻物質の伝導度および剛性率を,モンテカルロ法を用いて定量的に検討した.剛性率の結果を中性子星の非径方向振動のスペクトル解析へ応用した.
    5.量子ク-ロン固体の状態方程式
    ク-ロン固体について径路積分表示に基づく量子モンテカルロ計算を行ない,全温度・密度領域に渡って正確な状態方程式を導いた.
    6.スピン密度汎関数法によるヘリウム原子基底状態の解析
    密度汎関数法に基づき,交換・相関エネルギ-汎関数に対するスピン依存性や非局所密度依存性を取り入れ,かつ自己相互作用を含まない形の計算手法を定式化し,ヘリウム原子基底状態の解析からその有効性を確かめた.

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  • 高密度多種イオンプラズマの相状態と輸送過程

    研究課題/領域番号:62580001  1987年 - 1988年

    日本学術振興会  科学研究費助成事業 一般研究(C)  一般研究(C)

    一丸 節夫, 家富 洋, 田中 成典

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    配分額:1800000円 ( 直接経費:1800000円 )

    補助金が交付された期間に得られた研究成果を以下の1〜3に分けて述べる。
    1.代表者は分担者と協力して、強結合プラズマの統計物理とそき応用につて1986年迄の成果をレビューし、Physics Reports誌に公刊した。1986年迄の研究成果のうち、本課題研究に関連の深いものとして、(1)電子遮蔽効果を取り入れたイオン系の自由エネルギーをhypernetted chain(HNC)近似内で正確に計算する公式の導出、(2)太陽内部条件下での水素プラズマ中の鉄イオン溶融度曲線の計算、(3)密度汎関数法に基づくブリッジ関数の新しい表式の導出とそれによるHNC法の改良、が挙げられる。
    2.古典一成分プラズマがbcc結晶相に固化する条件を、改良されたHNC法による直接相関関数を用いて、密度汎関数法で解析した。粒子間相対座標の3体相関や角度相関の効果を微視的計算により明らかにし、固化条件を計算するための簡便な方法を提案した。
    3.白色矮星内部条件に対応する高密度炭素-酸素混合物質の状態方程式をモンテカルロ・シミュレーション法・積分方程式法・密度汎関数法を用いて解析した。その結果、炭素-酸素二種イオン混合プラズマでは、固相液相の両方で、線型混合則が、精度よく成り立つことを示した。次に、炭素-酸素二種イオン混合プラズマの固化に伴う相図を正確に計算し、それが共沸型(azeotropic)であることを示した。さらに相変化に伴う質量密度の不連続なとびを評価した。これらの計算結果は白色矮星の進化過程を解析するのに重要である。

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  • 高密度多種イオンプラズマにおける相分離及び共晶現象の研究

    研究課題/領域番号:61780004  1986年

    日本学術振興会  科学研究費助成事業 奨励研究(A)  奨励研究(A)

    家富 洋

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    配分額:900000円 ( 直接経費:900000円 )

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  • 固体電解質の電子状態とイオン輸送

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    資金種別:競争的資金

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  • Structural and Dynamical Properties of Multicomponent Glasses

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    資金種別:競争的資金

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  • 多成分ガラスの構造およびダイナミックス

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    資金種別:競争的資金

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  • 強結合プラズマ物性に関する研究

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    資金種別:競争的資金

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  • Moleculer Dynamics Simulaton Study on Nanomaterials

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    資金種別:競争的資金

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  • Electronic Properties and Ionic Transport in Solid Electrolytes

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    資金種別:競争的資金

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  • ナノマテリアルの分子動力学シミュレーション

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    資金種別:競争的資金

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