8,334 research outputs found
Filling dependence of a new type of charge ordered liquid on a triangular lattice system
We study the recently reported characteristic gapless charge ordered state in
a spinless fermion system on a triangular lattice under strong inter-site
Coulomb interactions. In this state the charges are spontaneously divided into
solid and liquid component, and the former solid part aligns in a Wigner
crystal manner while the latter moves among them like a pinball. We show that
such charge ordered liquid is stable over a wide range of filling, ,
and examine its filling dependent nature.Comment: 3 pages 3 figure
From China with love: Effects of the Chinese economy on skill-biased technical change in the US
In this study, we analyze the effects of labor shortage in China on the direction of innovation in the US by incorporating production offshoring into a North-South model of directed technical change. We �find that if offshoring is present (absent) in equilibrium, then a decrease (an increase) in unskilled labor in the South would lead to skill-biased technical change in the North. This fi�nding highlights the different implications of offshoring and conventional trade on innovation. Furthermore, we �find
that an increase in the Southern stock of capital reduces offshoring and also leads to skill-biased technical change. Therefore, rapid capital accumulation and labor shortage
in China could lead to a rising skill premium in the US. Calibrating the model to China-US data, we �find that a 1% decrease in unskilled labor (1% increase in capital)
in China leads to a 0.8% (0.6%) increase in the skill premium in the US under a moderate elasticity of substitution between skill-intensive and labor-intensive goods
A Monte Carlo Method for Fermion Systems Coupled with Classical Degrees of Freedom
A new Monte Carlo method is proposed for fermion systems interacting with
classical degrees of freedom. To obtain a weight for each Monte Carlo sample
with a fixed configuration of classical variables, the moment expansion of the
density of states by Chebyshev polynomials is applied instead of the direct
diagonalization of the fermion Hamiltonian. This reduces a cpu time to scale as
compared to for the
diagonalization in the conventional technique; is the dimension
of the Hamiltonian. Another advantage of this method is that parallel
computation with high efficiency is possible. These significantly save total
cpu times of Monte Carlo calculations because the calculation of a Monte Carlo
weight is the bottleneck part. The method is applied to the double-exchange
model as an example. The benchmark results show that it is possible to make a
systematic investigation using a system-size scaling even in three dimensions
within a realistic cpu timescale.Comment: 6 pages including 4 figure
Systems identification and application systems development for monitoring the physiological and health status of crewmen in space
The use of automated, analytical techniques to aid medical support teams is suggested. Recommendations are presented for characterizing crew health in terms of: (1) wholebody function including physiological, psychological and performance factors; (2) a combination of critical performance indexes which consist of multiple factors of measurable parameters; (3) specific responses to low noise level stress tests; and (4) probabilities of future performance based on present and periodic examination of past performance. A concept is proposed for a computerized real time biomedical monitoring and health care system that would have the capability to integrate monitored data, detect off-nominal conditions based on current knowledge of spaceflight responses, predict future health status, and assist in diagnosis and alternative therapies. Mathematical models could play an important role in this approach, especially when operating in a real time mode. Recommendations are presented to update the present health monitoring systems in terms of recent advances in computer technology and biomedical monitoring systems
Universality Class of Ferromagnetic Transition in Three-Dimensional Double-Exchange System - O(N) Monte Carlo Study -
Curie temperature and exponents are studied for the three-dimensional
double-exchange model. Applying the O(N) Monte Carlo algorithm, we perform
systematic finite-size scaling analyses on the data up to sites. The
obtained values of the critical exponents are consistent with those of the
Heisenberg universality class, and clearly distinct from the mean-field values.Comment: 3 pages including 2 figure
Non-Kondo mechanism for resistivity minimum in spin ice conduction systems
We present a mechanism of resistivity minimum in conduction electron systems
coupled with localized moments, which is distinguished from the Kondo effect.
Instead of the spin-flip process in the Kondo effect, electrons are elastically
scattered by local spin correlations which evolve in a particular way under
geometrical frustration as decreasing temperature. This is demonstrated by the
cellular dynamical mean-field theory for a spin-ice type Kondo lattice model on
a pyrochlore lattice. Peculiar temperature dependences of the resistivity,
specific heat, and magnetic susceptibility in the non-Kondo mechanism are
compared with the experimental data in metallic Ir pyrochlore oxides.Comment: 5 pages, 3 figures, accepted for publication in Physical Review
Letter
Ferromagnetic transition in a double-exchange system containing impurities in the Dynamical Mean Field Approximation
We formulate the Dynamical Mean Field Approximation equations for the
double-exchange system with quenched disorder for arbitrary relation between
Hund exchange coupling and electron band width. Close to the
ferromagnetic-paramagnetic transition point the DMFA equations can be reduced
to the ordinary mean field equation of Curie-Weiss type. We solve the equation
to find the transition temperature and present the magnetic phase diagram of
the system.Comment: 5 pages, latex, 2 eps figures. We explicitely present the magnetic
phase diagram of the syste
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