[Show abstract][Hide abstract] ABSTRACT: We present an analysis of the credit market of Japan. The analysis is
performed by investigating the bipartite network of banks and firms which is
obtained by setting a link between a bank and a firm when a credit relationship
is present in a given time window. In our investigation we focus on a community
detection algorithm which is identifying communities composed by both banks and
firms. We show that the clusters 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. Specifically, we obtain communities of banks and networks
for each of the 32 investigated years, and we introduce a method to track the
time evolution of these communities on a statistical basis. We then
characterize communities by detecting the simultaneous over-expression 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 clusters of banks and firms together with a slow dynamics 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.
[Show abstract][Hide abstract] ABSTRACT: We have analyzed the Indices of Industrial Production (Seasonal Adjustment
Index) for a long period of 240 months (January 1988 to December 2007) to
develop a deeper understanding of the economic shocks. The angular frequencies
estimated using the Hilbert transformation, are almost identical for the 16
industrial sectors. Moreover, the partial phase locking was observed for the 16
sectors. These are the direct evidence of the synchronization in the Japanese
business cycle. We also showed that the information of the economic shock is
carried by the phase time-series. The common shock and individual shocks are
separated using phase time-series. The former dominates the economic shock in
all of 1992, 1998 and 2001. The obtained results suggest that the business
cycle may be described as a dynamics of the coupled limit-cycle oscillators
exposed to the common shocks and random individual shocks.
[Show abstract][Hide abstract] ABSTRACT: 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.
Journal of Economic Interaction and Coordination 05/2012; 10(1). DOI:10.1007/s11403-013-0118-9 · 0.57 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The electronic band calculations of noble metal halides are studied to make the high ionic conducting origin of silver and cupper ions clear using the tight-binding method. The d bands of Ag ions are much more weakly coupled with the p bands of halogen ions, while those of Cu ions 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 primary stems from combination of the deformability of the d shell and the weakness of the p-d hybridization.
International Journal of Modern Physics B 01/2012; 15(06n07). DOI:10.1142/S0217979201005155 · 0.94 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We investigate a Japanese transaction network consisting ofabout 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.
[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: 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.
Solid State Communications 11/2011; 151(21):1605-1608. DOI:10.1016/j.ssc.2011.07.020 · 1.90 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: 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.