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Toshinao Akuzawa, Miki Wadati
Subject area: Mathematical methods in physics.
1998 Volume 67 Issue 7 Pages
2151-2154
Published: July 01, 1998
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It was conjectured by Jackson et al. that the finite volume effective partition function of QCD with the topological charge M-N coincides with the Itzykson-Zuber type integral for M× N rectangular matrices. In the present article we give a proof of this conjecture, in which the original Itzykson-Zuber integral is utilized.
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Chihiro Matsuoka, Masaru Sugii, Takeshi Iizuka, Takahi Hasegawa
Subject area: Statistical physics and thermodynamics.
1998 Volume 67 Issue 7 Pages
2155-2157
Published: July 01, 1998
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The propagation of active waves in a reaction-diffusion system with spatial inhomogeneity is examined using the geometrical shock dynamics method. The refraction or diffraction of active waves is found for the case that the diffusivity of the system changes with a spatial variable.
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Kazuhiro Fuchizaki, Kyozi Kawasaki
Subject area: Statistical physics and thermodynamics.
1998 Volume 67 Issue 7 Pages
2158-2161
Published: July 01, 1998
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Through the mapping onto the kinetic lattice gas model the dynamical density functional equation is solved by the Monte Carlo method in a deeplysupercooled hard-sphere liquid, while focusing on how the system exploresthe free-energy landscape during a relaxation process. A variety ofmetastable states appear as the supercooling proceeds beyond the equilibriumcrystallization point. Our approach is the first to reproduce the hoppingtransitions among these states as a solution of a mesoscopic kinetic equation.
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Masatoshi Misono, Kazuyuki Nakayama, Toshiro Kohmoto, Yukio Fukuda, Ma ...
Subject area: Optics.
1998 Volume 67 Issue 7 Pages
2162-2165
Published: July 01, 1998
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An experiment of stochastic resonance (SR) using well-characterized colored noise was performed in an optical bistable system. The resonance signal peculiar to SR was observed, and the dependence of the resonance signal on the noise cutoff frequency was studied. The SR experiment was well reproduced by a numerical simulation using a model system.
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Shigeo Kida, Hideaki Miura
Subject area: Fluid dynamics.
1998 Volume 67 Issue 7 Pages
2166-2169
Published: July 01, 1998
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A numerical method of extraction of the axis of tubular vortices in turbulent flows, which was previously proposed by Miura and Kida [J. Phys. Soc. Jpn. 66 (1997)], is improved by imposing a swirl condition. This condition guarantees the extraction of low-pressure vorticeswith swirling motion as well as the demarcation of the core regionsaround the central axis. The mean radius of vortex cores is found to be five to six times the Kolmogorovlength in turbulence of micro-scale Reynolds number of 46.
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Jun–ichi Sakai, Masanori Eda, Hiroyuki Miyazaki, Torsten Neubert
Subject area: The physics of plasmas and electric discharges.
1998 Volume 67 Issue 7 Pages
2170-2173
Published: July 01, 1998
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Using a two-dimensional electromagnetic and relativistic particle code, we show that electromagnetic waves can be emitted in pair plasmasfrom a region where the Kelvin-Helmholtz instability occurs.
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Kazuki Koshino, Tetsuo Ogawa
Subject area: Lattice dynamics and crystal statistics.
1998 Volume 67 Issue 7 Pages
2174-2177
Published: July 01, 1998
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The possibility of occurrence of cooperative structural changesis investigated using a minimal model composed of localized electrons andclassical lattices under the adiabatic approximation.In particular, the relaxation after one-photon absorption at a siteis examined in detail. This relaxation proceeds in two steps.First, a local structural change is created due to the lattice relaxationassociated with the local electronic excitation.After the spontaneous emission of a photon, this local structural change (a) remains locally, (b) induces a global structural change cooperatively, or(c) disappears and returns to the initial phase.Dynamical features of the case (b) are shown to be characterized by the domino effect.This global structural change occurs onlywhen the intersite interaction is short-ranged and moderately strong.
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Shinya Yoshioka, Yuhji Tsujimi, Toshirou Yagi
Subject area: Equations of state, phase equilibria, and phase transitions.
1998 Volume 67 Issue 7 Pages
2178-2181
Published: July 01, 1998
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Impulsive stimulated Raman scattering experiment has been performed in KDP (KH
2PO
4) to directly observe the time-dependent feature of the ferroelectric soft B
2 mode in the polariton regime. The underdamped soft oscillatory mode has been observed and its squared natural frequency ω
02 shows the linear temperature dependence, ω
02 ∝ T-T
0 where T
0 is the phase transition point of the clamped crystal. The present results are consistent with the previous study of the forward Raman scattering at room temperature. It is pointed out that the polariton behavior is explained by the order-disorder type mechanism of the phase transition as well as in the phonon-polariton scheme expected for the displacive type.
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Ho Young Ahn, Se Young Jeong, Il Kwon Moon, Yoon Hee Jeong
Subject area: Thermal properties of condensed matter.
1998 Volume 67 Issue 7 Pages
2182-2184
Published: July 01, 1998
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Single crystals of K
2ZnCl
4 with high purity were grown by theCzochralski method inorder to avoid the strong influence of water remaining in the crystal.The heat capacity for a single crystal was measured for cooling as wellas heating runs, using a home-built adiabatic calorimeter with a temperatureprecision of 1 mK. The existence of a low-temperature incommensurate phase was revealed in these measurements for the first time. On heating, two sharp peaks were found at146.983 ± 0.002 K (peak I) and at 146.956 ± 0.002 K (peak II), and the temperature interval between the two peaks amounted toapproximately 0.027 K. These peaks showed a thermalhysteresis of about 0.1 K. The shapes of peak II obtained on bothheating and cooling measurement are characteristic of a commensurate -incommensurate phase transition.
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Noriaki Kimura, Takemi Komatsubara, Dai Aoki, Yoshichika Onuki, Yoshin ...
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 7 Pages
2185-2188
Published: July 01, 1998
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We have performed the de Haas-van Alphen (dHvA) experiments in UPt
3.A new branch has been observed in a relatively wide angle region.It has a large cyclotron effective mass of 80, m_0 and the dHvA frequencyis 5.66 × 10
7, Oe for the field along the [0001] direction.The new branch most likely corresponds to the main electron Fermi surface in the 37th band of the 5f-itinerant band model.
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Hiroyuki Shima, Tsuneyoshi Nakayama
Subject area: Electronic transport in condensed matter.
1998 Volume 67 Issue 7 Pages
2189-2192
Published: July 01, 1998
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It is demonstrated that the finite-time scaling approach, derived from the forced oscillator method, to determine the exponent of the ac conductivity σ (ω )∝ ω
δ near the metal-insulator transition point is a very powerful method for evaluating the precise value of the exponent δ with high speed and accuracy.
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Hideyuki Sato, Yoshihiko Kobayashi, Kenichi Hashimoto, Yuji Aoki, Hito ...
Subject area: Electronic transport in condensed matter.
1998 Volume 67 Issue 7 Pages
2193-2196
Published: July 01, 1998
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We have measured the thermoelectric power and Hall effect on three Co--Al--O granular films whose conduction mechanism varies from metallic to tunneling type depending on O content. We obtained a finite thermoelectric power (TEP) which decreases with increasing resistivity. In the tunneling type sample, a large field dependence of TEP correlated with the magnetoresistance has been observed. The Hall coefficient of Co--Al--O decreases with increasing sample resistivity, in contrast with the giant Hall effect reported for Ni--SiO
2 granular sample with a similar resistivity. The dominant electronic conduction mechanisms are found to be different between the giant magnetoresistance and the giant Hall effect in ferromagnetic-metal-oxide granular systems.
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Yoshiaki Ono
Subject area: Magnetic properties and materials.
1998 Volume 67 Issue 7 Pages
2197-2200
Published: July 01, 1998
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Metamagnetism of heavy fermions is investigated using the Anderson lattice model in which the anisotropy of the hybridization matrix element, together with electron-lattice coupling, is taken into account. Within the leading-order approximation in the 1/N-expansion, it is found that the incoherent part of the f electron becomes relevant above a critical field H
M, while it is irrelevant below H
M.Consequently, both magnetization and magnetostriction show abrupt increases with increasing H at H
M.The results are in good agreement with the experimental data of CeRu_2Si_2.
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Hidetaka Fukuda, Karim Kadir, Yasuyoshi Matsumoto, Takashi Suzuki, Hir ...
Subject area: Magnetic properties and materials.
1998 Volume 67 Issue 7 Pages
2201-2204
Published: July 01, 1998
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We performed the magnetic susceptibility, specific heat and electrical resistivility measurements on RMg
2Ni
9 where R=La, Ce, Pr, Nd and Gd. RMg
2Ni
9 crystallizes in a hexagonal PuNi
3-type structure, in which the R atoms are in a two-dimensional arrangement. The results indicate that CeMg
2Ni
9 is a valence fluctuated compound with γ =80, mJ/mol· Ce· K
2, but the magnetic susceptibility and the electrical resistivility do not show any broad peak at a finite temperature. Even for R=Gd, no magnetic ordering is observed at 2, K. The unusual physical properties of RMg
2Ni
9 are obviously influenced by the two-dimensional arrangement of rare earth in the c-plane.
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Yoshiyuki Fukumoto, Akihide Oguchi
Subject area: Magnetic properties and materials.
1998 Volume 67 Issue 7 Pages
2205-2208
Published: July 01, 1998
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The uniform susceptibility and triplet excitation spectrum of the Heisenberg antiferromagnet on the one-fifth depleted square lattice are calculated using the third-order perturbation expansion method from the viewpoint of the weakly coupled meta-plaquette picture. Both the susceptibility and triplet excitation spectrum data for CaV
4O
9 are simultaneously explained. The origin of the relatively large spin gap in this compound is discussed.
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Masayuki Hagiwara, Kazuhiko Minami, Yasuo Narumi, Keiji Tatani, Koichi ...
Subject area: Magnetic properties and materials.
1998 Volume 67 Issue 7 Pages
2209-2211
Published: July 01, 1998
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We report the results of magnetic measurements on a powder sample of NiCu(pba)(D
2O)
3· 2D
2O (pba=1, 3-propylenebis(oxamato)) which is one of the prototypical examples of an S=1/2 and 1 ferrimagneticchain. Susceptibility(χ) shows a monotonous increase with decreasing temperature (T) and reaches a maximum at about 7 K. In the plot of χ T versus \it{T}, the experimental data exhibit a broad minimum and are fit to the χ T curve calculated for the ferrimagneticHeisenberg chain composed of S=1/2 and 1. From this fit, we have evaluated the nearest-neighbor exchange constant J/k
B=121 K, the g-values of Ni
2+ and Cu
2+, g
Ni=2.22 and g
Cu=2.09, respectively.Applied external field dependence of χ T at low temperatures is reproduced fairly well by the calculation for the same ferrimagnetic model.
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Yutaka Itoh, Ayako Tokiwa–Yamamoto, Takato Machi, Keiichi Tanabe
Subject area: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1998 Volume 67 Issue 7 Pages
2212-2214
Published: July 01, 1998
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We observed the pseudo spin-gap behavior in the T-dependences of
63Cu Knight shift and NMR relaxation rates, as well as electrical resistivity, over a wide doping range for the bilayer high-T
c HgBa
2CaCu
2O
6+δ using
63Cu NMR spin-echo technique. We found a difference in the doping dependence of the pseudo spin-gap behavior between HgBa
2CaCu
2O
6+δ and the previous monolayer HgBa
2CuO
4+δ. The results indicate that the pseudo spin-gap behavior strongly depends on the underlying electronic states.
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Yoshiyuki Matsumoto
Subject area: Optical properties and condensedmatter spectroscopy and other interactions of matter with particles and radiation.
1998 Volume 67 Issue 7 Pages
2215-2217
Published: July 01, 1998
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Raman scattering from a single crystal of Rb
3H(SeO
4)
2 has been observed in the frequency range between 20cm
-1 and 1000cm
-1 at phases I (482.6K, 466.8K, 443.3K) and II (391.2K, 301.2K, 78.6K). The measured spectra in phase II were assigned to the normal modes of SeO
4 tetrahedra vibration. In phase I, this compound shows high electric conductivity due to the hopping of protons. A new Raman line has been found at 826cm
-1 in this high temperature phase. It is suggested that this line is caused by the stretching mode of a single Se--O bond in SeO
4 tetrahedra, accompanied by destruction and reconstruction of hydrogen bonds.
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M. F. Lin
Subject area: Optical properties and condensedmatter spectroscopy and other interactions of matter with particles and radiation.
1998 Volume 67 Issue 7 Pages
2218-2221
Published: July 01, 1998
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The π-electron states of carbon toroids are obtained from thetight-binding model. The low-frequency absorption spectra are studiedwithin the gradient approximation. They exhibit rich peak structures, mainly owing to the inter-π-state and the intra-π-state excitations.In general, spectral intensity and excitation energiesstrongly depend on the toroidal geometry (chiral angle, radius, and width), the temperature (T), and the magnetic flux (φ).However, armchair carbon toroids only exhibit one specialpeak, and their absorption spectra are hardly affected by T and φ.
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Masanori Cho
Subject area: Physical chemistry.
1998 Volume 67 Issue 7 Pages
2222-2225
Published: July 01, 1998
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By examining the change in dynamic light scattering spectra, we assumed the existence of the coexistent phase of the sol and gel phases in the temperature range from 300K to the sol-gel transition point (T
g). The temperature dependence of the volume fraction of the gel phase (φ
g) could be measured in the sol phase as φ
g=Φ/(T-T
φ) (T
g<T<300K), where Φ=0.635K and T
φ=288.5K. It was also found that the temperature dependence of the gelatin solution viscosity (η) obeys the Vogel-Fulcher law. From the temperature dependences of φ
g and η, we propose the following simple equation that relates η to φ
g, η=η
0exp(23.0φ
g), where η
0 is a constant.
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Bireswar Basu–Mallick
Subject area: Mathematical methods in physics.
1998 Volume 67 Issue 7 Pages
2227-2233
Published: July 01, 1998
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By using `anyon like' representations of permutation algebra, which pick up nontrivial phase factors while interchanging the spins of twolattice sites, we construct some integrable variants of Haldane-Shastry (HS)spin chain. Lax equations for these spin chains allow us to findout the related conserved quantities. However, it turns out that such spin chains also possess a few additional conserved quantities which are apparently not derivable from the Lax equations. Identifying these additional conserved quantities, and the usual ones related to Lax equations, with different modes of a monodromy matrix, it is shown that the above mentioned HS like spin chains exhibit multi-parameter deformed and`nonstandard' variants of Y(gl
M) Yangian symmetry.
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Ryogo Hirota
Subject area: Mathematical methods in physics.
1998 Volume 67 Issue 7 Pages
2234-2236
Published: July 01, 1998
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The potential form of the modified KdV equation: \frac{∂ φ}{∂ t} + 8(\frac{∂ φ}{∂ x})
3 + \frac{∂
3 φ}{∂ x
3} = 0, is discretized in the following form: tan (φ^{m+\frac12}
n-φ^{m-\frac12}
n) = δ tan (φ
m_{n-\frac12}-φ
m_{n+\frac12}), which is shown to be a 4-reduction of the discrete analogue of a generalized Toda equation.
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Yasumasa Kajinaga, Miki Wadati
Subject area: Mathematical methods in physics.
1998 Volume 67 Issue 7 Pages
2237-2241
Published: July 01, 1998
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Using a lattice version of the Miura transformation between two nonlinear evolution systems called the Volterra lattice and the modified Volterra lattice, we have obtained a pair of Bäcklund transformations for the Volterra lattice onto itself. By this form of the transformations, we can show the relation between the inverse scattering problems and the discrete Miura transformation, then derive the conservation laws and the superposition formula. In a suitable continuum limit, they reduce to be a complete analogue of the Bäcklund transformations for the Korteweg-de Vries equations first obtained by Wahlquist and Estabrook.
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Yukiko Umeno, Masahiro Shiroishi, Miki Wadati
Subject area: Mathematical methods in physics.
1998 Volume 67 Issue 7 Pages
2242-2254
Published: July 01, 1998
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We propose a new type of the Yang-Baxter equation (YBE) and the decorated Yang-Baxter equation (DYBE). Those relations for the fermionic R-operatorwere introduced recently as a tool to treat the integrability of the fermion models. Using the YBE and the DYBE for the XX fermion model, we construct the fermionic R-operator for the one-dimensional (1D) Hubbard model. It gives another proof of the integrability of the 1D Hubbard model. Furthermore a new approach to the SO(4) symmetry of the 1D Hubbard modelis discussed.
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Kazuhiko Minami
Subject area: Statistical physics and thermodynamics.
1998 Volume 67 Issue 7 Pages
2255-2269
Published: July 01, 1998
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The susceptibility in arbitrary directions, the specific heat, the energy and the magnetization of general Ising-type chains are exactly expressed in terms of the eigenvectors of the transfer matrix corresponding to the Ising-type interaction. These quantities, as a result, can be explicitly obtained for small spin values and generally obtained from the solution of corresponding eigenvalue problem of finite degree. Numerical estimations are easy for arbitrary spin values. This formula includes the spin-S transverse Ising model with vanishing or non-vanishing parallel external field, the Blume-Emery-Griffiths model and the Blume-Capel model, mixed spin and mixed bond periodic systems such as alternating Ising chains or Ising ferrimagnets and also includes Ising models with random structures. Low temperature behaviors of these systems and the crossover to infinite spin systems are also investigated.
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Shin–ichi Tadaki, Macoto Kikuchi, Yuki Sugiyama, Satoshi Yukawa
Subject area: Statistical physics and thermodynamics.
1998 Volume 67 Issue 7 Pages
2270-2276
Published: July 01, 1998
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A coupled map traffic flow model is introduced, basedon optimal velocity functions. The model is simulatedunder open boundary conditions. Effects of noises invelocity are investigated. The average car densityincreases with the noise level. The high throughput flow isrealized when the noise level is sufficiently large, andpower law behavior appears in temporal spectra of densityfluctuations at the same time. By introducing trafficbottlenecks, a hysteresis loop, which indicates theemergence of traffic jams, is observed in theheadway-velocity plane. Temporal spectra of densityfluctuations also obey a power law in this case, whoseexponent is independent of the noise level.
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Koichiro Shida, Wm. G. Hoover
Subject area: Statistical physics and thermodynamics.
1998 Volume 67 Issue 7 Pages
2277-2280
Published: July 01, 1998
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“Thermal Creep” is a steady streaming motion, induced by atemperature gradient parallel to a fluid boundary, in theabsence of gravity. Thermal creep has been studied by Maxwell, analyzed by Kennard, and simulated by Ibsen, Soto, and Cordero. Here we report several two-dimensional simulations. We find that the creep velocity is sensitive to the imposed macroscopicboundary conditions and that the agreement with existingtheoretical predictions is only semiquantitative.
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Masahiro Nakagawa
Subject area: Statistical physics and thermodynamics.
1998 Volume 67 Issue 7 Pages
2281-2293
Published: July 01, 1998
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In this paper we shall propose a novel chaos neural network model applied to the chaotic autoassociation memory. The present artificial neuron model is properly characterized in terms of a time-dependent periodic activation function to involve a chaotic dynamics as well as the energy steepest descent strategy. It is elucidated that the present neural network has a remarkable ability of the dynamic memory retrievals beyond the conventional models with the nonmonotonous activation function as well as such a monotonous activation function as sigmoidal one. This advantage is found to result from the property of the analogue periodic mapping accompanied with a chaotic behaviour of the neurons. It is also concluded that the present analogue neuron model with the periodicity control has an apparently large memory capacity in comparison with the previously proposed association models.
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Takeya Tsurumi, Miki Wadati
Subject area: Statistical physics and thermodynamics.
1998 Volume 67 Issue 7 Pages
2294-2299
Published: July 01, 1998
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We investigate the propagation of nonlinear pulses in a magnetically trapped Bose-Einstein condensate. The condensate may take an elongated shapejust like a “cigar”, because of high asymmetry of the harmonic trap. By applying the reductive perturbation method to model equations, we derive the Korteweg-de Vries equation, and show a formula for thedependence of the pulse speed on its amplitude.
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Hideo Ikeda, Yasuhiro Kasai
Subject area: Statistical physics and thermodynamics.
1998 Volume 67 Issue 7 Pages
2300-2305
Published: July 01, 1998
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An Ising spin system can be expressed as a percolation system, formulated by Kasteleyn and Fortuin (KF), of the spin clusters coupled by interactions effective against the thermal agitation. For the 2D strongly-frustrated Ising spin system, the free energy does not show any criticality at the percolation transition temperature of the explicit singularity in the KF-percolation generating function. By extending it into a frustrated Potts spin system with a general degree of internal freedom, the criticality of KF-percolation expression becomes explicit in the ordinary free energy. The universality class belongs to the ferromagnetic Potts model with the half degree of its Potts spin freedom; this means that the effective spin freedom of the frustrated Ising spin system is unity.
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Katsuya Ishii, Shizuko Adachi, Tsutomu Kambe
Subject area: Fluid dynamics.
1998 Volume 67 Issue 7 Pages
2306-2314
Published: July 01, 1998
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A theory of vortex sound formulated in the form of multipole expansions is applied to the oblique collision of two vortex rings at right angles. Using the theoretical formula for the far-field acoustic pressure excited by a time-dependent localized vorticity distribution, the coefficients of the multipole modes of the wave pressure are estimated by the numerical data of computer simulation. Time evolution of the vorticity field is obtained by solving a viscous incompressible vorticity equation with a vorticity-potential method developed for a three-dimensional vorticity field in a bounded domain. Numerical simulations are carried out for two kinds of vortex rings with the same core parameters but different ring radii, and the details of the vortex motion during the oblique collision are studied numerically. Computed main-mode amplitudes of the wave pressure excited by the vortex motion are found to be consistent with those of the experimentally observed acoustic wave not only qualitatively but also quantitatively. From comparison of the quadrupole and octapole modes of the far-field acoustic pressure between the computation and the experiment, it is possible to estimate the slenderness ratio of a core radius to a ring radius of the experimental vortex ring. It is remarkable that the present simulation gives data identifying the source region for the wave emission.Strong acoustic source is identified at the location where vorticity field varies very rapidly during vortexline reconnection.
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Akira Tsushima, Satoshi Kabaya
Subject area: The physics of plasmas and electric discharges.
1998 Volume 67 Issue 7 Pages
2315-2321
Published: July 01, 1998
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An ion drift velocity at a sheath edge v
D in a bounded plasma with a finite ion temperature is studied using a one-dimensional electrostatic particle simulation code.This code includes spatially uniform particle generation and electron heating and determines v
D at the sheath edge, defined by (n
i - n
e) / n
i = 0.1 with an ion density n
i and an electron density n
e.In comparison with the ion acoustic velocity from the fluid equations, v
D = √(T
ecenter + γ T
iedge) / m
i is obtained, where T
ecenter is an electron temperature at the plasma center, T
iedge is an ion temperature at the sheath edge, m
i is an ion mass, and γ = (3.5 + T
iedge / T
ecenter) / (1 + T
iedge / T
ecenter).It is also found that a sheath potential change little but an ion acceleration potential in a presheath decreases with the increasing T
iedge / T
ecenter.
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Tomoya Tatsuno, Masahiro Wakatani
Subject area: The physics of plasmas and electric discharges.
1998 Volume 67 Issue 7 Pages
2322-2326
Published: July 01, 1998
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The MHD wave is studied when two steep density gradient regions exist at surfaces of slab plasma.In such a case, it is shown that the surface Alfvén wave has two branches with nearly the same damping rates, since the steep density gradients are located closely each other.However, for the sharp boundary plasma, the surface Alfvén wave does not damp.As the density profile is relaxed, the damping rates become larger, pass via extremum, and again they become small when the scale length of the density gradients extremely increases.These damping rates seem consistent with behavior of magnetic fluctuations observed in the Heliotron-E pellet injection experiment.
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Jiri Hlinka, Yoshihiro Ishibashi
Subject area: Equations of state, phase equilibria, and phase transitions.
1998 Volume 67 Issue 7 Pages
2327-2329
Published: July 01, 1998
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An analytical method is presented, on the basis of a discrete model, for evaluation of the potential barrier to be surmounted when the stable commensurately modulated structure is displaced by one lattice distance. A concrete example is given for the case where there occurs a phase transition between two commensurate phases with the same modulation period.
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Hiroshi Tochihara, Yoshimichi Nakamura, Hiroshi Kawai, Masatoshi Nakay ...
Subject area: Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties).
1998 Volume 67 Issue 7 Pages
2330-2334
Published: July 01, 1998
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The structure of a Si(001) surface with monatomic steps is investigated by means of scanning tunneling microscopy at 95, K and Monte Carlo simulations (MCS) at various temperatures. In particular, we pay attention to the effect of kinks at the step edge on the formation of c(4× 2) domains, and both studies reveal that the kinks do not govern the growth of the domains. MCS demonstrates that the nucleation of c(4× 2) domains takes place at central regions of the terrace as a result of thermal fluctuation, and that the domains propagate to the step edge with decreasing temperature.
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Takao Yamamoto
Subject area: Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties).
1998 Volume 67 Issue 7 Pages
2335-2345
Published: July 01, 1998
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The relaxation process of the vicinal surface induced by the attachment-detachment mechanism is analyzed by the Ginzburg-Landau-Langevin equation based on the harmonically-interacting step (HIS) picture.By the equation, the time evolution of the step deformation width, the step fluctuation width and the step diffusion length is analyzed.For the relaxation process from small-fluctuation structure such as the ground-state structure, these quantities show the “universal” scaling behaviors. To verify the result, we performed the Monte-Carlo calculations for the free-Fermion terrace-step-kink (TSK) model and the solid-on-solid step TSK model.The result from the Monte-Carlo calculations agrees with the analytic result from the HIS picture quantitatively.For the relaxation process from the rough-surface structure, the “non-universal” scaling behaviors are obtained from the HIS analysis.
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Atsushi Tsuruta, Yoshiaki Ono, Tamifusa Matsuura, Yoshihiro Kuroda
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 7 Pages
2346-2362
Published: July 01, 1998
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In the previous studies, we examined roles of infrared divergences in pseudo-particle spectra in the impurity Anderson models with use of the expansion from the limit of the large spin-orbital degeneracy (1/N-expansion). Here, such studies are extended to obtain renormalized forms of frequency-/temperature-dependence of physical quantities such as scattering rate of conduction electrons and spin-, pseudo-spin- and charge-susceptibility, where the pseudo-spin represents the channel's degree of freedom, by collecting the most infrared-divergent terms in the 1/N-expansion. The results reconfirm that in single channel models the infrared divergent terms in the pseudo-particle spectra are completely cancelled by the vertex corrections at each order of the 1/N-expansion, while in multichannel models the cancelation becomes incomplete and the terms remain in the physical quantities.
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Peter Thalmeier, Ryousuke Shiina, Hiroyuki Shiba, Osamu Sakai
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 7 Pages
2363-2371
Published: July 01, 1998
Released on J-STAGE: October 01, 1999
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A theory for the multipolar excitations in theantiferro-quadrupolar (AFQ) phase of CeB
6 is developed. It is based on a pseudo-spin model for the Γ
8 ground state of Ce used previously to explain the B-T phase diagram. An equation of motion method for the multipolar operators is employed and the solutions for the O
20 and O
xy phases are given. It is shown that the excitation branches are classified as being of mixed quadrupolar-dipolar, quadrupolar-octupolar and octupolar-dipolar character. The former two have strong and the latter only weak dispersion respectively. The transition from the O
20 to the O
xy phase in the symmetric model is accompanied by the reappearance of a quadrupolar Goldstone mode. In the O
xy phase of the asymmetric model some modes are gapped already at zero field and for finite field no Goldstone mode remains. In addition we give a derivation for the dynamical structure function based on the mixing scheme of multipolar excitations and discuss the result for the zero-field case.
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Tadao Kasuya
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 7 Pages
2372-2382
Published: July 01, 1998
Released on J-STAGE: October 01, 1999
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Mechanism of the unusual continuous transition in CeRu
2Si
2 from valence fluctuation regime to Kondo regime, in which the Fermi surface volume changes exactly by one electron, is studied in detail. The transition occurs due to the singlet bonding Kondo band, which becomes sharper and more dispersionless as it approaches the Fermi energy with weakening quasiparticle character and crosses the Fermi energy at the transition. Various anomalous properties are related also with the mixed valence character in the valence fluctuation regime, disappearing in the Kondo regime. An unusual behavior of Hall effect with a large and sharp peak at low temperature, which has been misunderstood as the anomalous Hall effect, is explained from the mechanism that there are two kinds of Fermi surfaces, the first group formed from small holes with weak c-f mixing, showing a little change at the transition, and the second group of large Fermi surfaces with strong c-f mixing changing nearly discontinuously at the transition. In the mixed valence state at low temperature, only the small holes contribute to the Hall current.
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C. R. Wang, H. S. Kuan, S. T. Lin, Y. Y. Chen
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 7 Pages
2383-2387
Published: July 01, 1998
Released on J-STAGE: October 01, 1999
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The metal-insulator (M-I) transition in Al--Pd--Re quasicrystals (QCs) was studied by annealing method. We found that increasing the resistivity ratio r=ρ (4.2, K)/ρ (300, K) of Al--Pd--Re QCs can greatly reduce the value of the electron correlation gap Δ and therefore drives the system towards and through the M-I transition. In the insulating state, the conductivity σ (T) between 0.5-- 7, K can be analyzed with σ (T)=σ
0 exp [-(T
0/T)]
1/4 and the negative magnetoconductance observed at low temperature is mainly attributed to the decrease of the localization length ξ with increasing field.
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Kyoko Nakada, Masatsura Igami, Mitsutaka Fujita
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 7 Pages
2388-2394
Published: July 01, 1998
Released on J-STAGE: October 01, 1999
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We study the π electronic structureof graphite ribbons of a nanometer width by taking account of the long-range electron-electron interaction.The primary features like energy dispersion and bond order distributionare essentially determined by the nearest-neighbor transfer alone, meaning their strong dependency on the connectivity relation in the π electron network.The Coulomb interaction, on the other hand, is induced by the sites of longer distances as well, which means thatthe Coulomb repulsion reflects the site geometry in the atomic configuration.We focus on the geometry-dependent Coulomb interaction and discuss how it influences the electronic state near the Fermi levelwhich is governed by the network topology.The Coulomb repulsion under the geometry of armchair ribbons works against the bond order distribution determined by the network topology.This may lead to a frustrated system especially for a quite narrow ribbon.The Coulomb interaction in zigzag ribbons tends to open a gapwith/without bond alternation depending on the ribbon width.The gap, however, keeps the flatness of the center bands around k = πand monotonically diminishes with increasing ribbon width, showing the anomalous character of the edge state.
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Yukihiro Shimizu, Osamu Sakai, Shunya Suzuki
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 7 Pages
2395-2407
Published: July 01, 1998
Released on J-STAGE: October 01, 1999
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We investigate the non-Fermi-liquid (NFL) behaviorof the impurity Anderson model (IAM)with non-Kramers doublet ground state of the f
, 2 configurationunder the tetragonal crystalline electric field (CEF).The low energy spectrum is explained by a combination of the NFLand the local-Fermi-liquid parts which are independent with each other.The NFL part of the spectrum has the same form to that oftwo-channel-Kondo model (TCKM).We have a parameter range that the IAM shows the - ln T divergenceof the magnetic susceptibility together with the positive magneto resistance.We point out a possibility that the anomalous properties ofU
xTh
1-xRu
2Si
2 including the decreasing resistivity with decreasing temperature can be explained by the NFL scenario of the TCKM type.We also investigate an effect of the lowering of the crystal symmetry.It breaks the NFL behavior at around the temperature, δ /10, where δ is the orthorhombic CEF splitting.The NFL behavior is still expected above the temperature, δ/10.
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Takeshi Nakanishi, Nobuo Môri, Chizuko Murayama, Hiroki Takahash ...
Subject area: Electronic transport in condensed matter.
1998 Volume 67 Issue 7 Pages
2408-2414
Published: July 01, 1998
Released on J-STAGE: October 01, 1999
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We report the electrical resistivity, the Hall coefficient, R
H, and the magnetoresistance, MR, at pressures up to 2.0 GPa, of the spin-ladder compound Sr
14-xCa
xCu
24O
41+δ, on both a polycrystal (x = 13.6) and single crystals (x = 11 and 12), in which superconductivity has been observed only in a range of both Ca content (-- 11 < x < 14) and pressure (-- 1.5 < P < -- 8 GPa). The pressure dependence of the R
H, with positive sign, indicates thatcarrier density increases with increasing pressure and localization of holecarriers at low temperature is substantially suppressed by applyingpressure. We have also found that a positive MR, which violates Kohler'srule, seems to appear below the temperature at which a spin gap begins toopen and strongly depends on the temperature as well as both on Ca contentand applied pressure, suggesting that this MR is closely related to themobile holes in the spin singlet state.
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Keiji Itoh, Takesi Usuki, Shigeru Tamaki
Subject area: Electronic transport in condensed matter.
1998 Volume 67 Issue 7 Pages
2415-2420
Published: July 01, 1998
Released on J-STAGE: October 01, 1999
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Electronic and ionic conductivities and thermoelectric power of liquid In
1-x--Se
x system have been measured as a function of concentration and temperature. The electronic conductivity in the system shows a deep minimum near the Se composition x=0.58 and the ionic conductivity has a broad maximum at this composition, where the thermoelectric power shows a large negative maximum. The electronic conductivity and thermoelectric power were analyzed in terms of the Fermi-Dirac integrals. It is found that the shape of the density of state, N(E), changes gradually with concentration.
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Nguyen Hong Shon, Tsuneya Ando
Subject area: Electronic transport in condensed matter.
1998 Volume 67 Issue 7 Pages
2421-2429
Published: July 01, 1998
Released on J-STAGE: October 01, 1999
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In a self-consistent Born approximation, the density of states and the conductivity are calculated in a two-dimensional graphite sheet in magnetic fields.Two different cases of scatterers are considered, the short-range case where the range is smaller than the lattice constant and the long-range case where it is comparable or slightly larger.The quantum theory provides results quite different from the results of Boltzmann transport theory even in the absence of a magnetic field.In high magnetic fields, the conductivity exhibits a series of peaks, whose values depend only on the natural constants and the Landau level index.The conductivity of undoped systems is always given by a universal conductivity e
2/π
2(h/2π) independent of a magnetic field.
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Arisato Kawabata
Subject area: Electronic transport in condensed matter.
1998 Volume 67 Issue 7 Pages
2430-2438
Published: July 01, 1998
Released on J-STAGE: October 01, 1999
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Electron conduction in one-dimensional system is investigated explicitlytaking into account the reservoirs to which 1D channel is connected at its ends.We calculate the current driven by the chemical potential difference of tworeservoirs, using the linear response theory by Kubo. At 0K, the conductance of1D channel is expressed in terms of one-electron Green's functions even in thepresence of the interaction, in contrast to the theory based on Kubo formula, inwhich two-electron Green's functions are essentially involved. The formalism inthis paper provides a new interpretation of Landauer formula. As regards theinteraction effects, the conductance of Fermi liquid without potential scatteringis2e
2/h, while that of Tomonaga-Luttinger liquid deceases with powerlow as the length of 1D channel increases.
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Nam Lyong Kang, Jai Yon Ryu, Sang Don Choi
Subject area: Electronic transport in condensed matter.
1998 Volume 67 Issue 7 Pages
2439-2443
Published: July 01, 1998
Released on J-STAGE: October 01, 1999
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Utilizing state-independent projection operators, we present a new optical conductivity formula for cyclotron transition in the system of electrons interacting anisotropically with phonons. The line-shape factor appearing in the conductivity tensor contains the many body effects for electrons and phonons. Applying this formula, we determine the two deformation potentials (dilation potential Ξ
d and uniaxial shear potential Ξ
u) of Ge in the quantum limit. By fitting the present theoretical values with the experimental data of Murase, Enjouji and Otsuka [J. Phys. Soc. Jpn. 29 (1970) 1248] and Kobori, Ohyama and Otsuka [J. Phys. Soc. Jpn. 59 (1990) 2141], we obtain Ξ
u=17.0± 0.6, eV and Ξ
d=-10.88± 0.47, eV.
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Wataru Izumida, Osamu Sakai, Yukihiro Shimizu
Subject area: Electronic transport in condensed matter.
1998 Volume 67 Issue 7 Pages
2444-2454
Published: July 01, 1998
Released on J-STAGE: October 01, 1999
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The tunneling conductance is calculated as a function ofthe gate voltage in wide temperature range for the singlequantum dot systems with Coulomb interaction.We assume that two orbitals are active for the tunneling process.We show that the Kondo temperature for each orbital channelcan be largely different.The tunneling through the Kondo resonance almost fullydevelops in the region T <~ 0.1 T
K* -- 0.2T
K*, where T
K* is the lowest Kondotemperature when the gate voltage is varied.At high temperatures the conductance changes to the usualCoulomb oscillations type.In the intermediate temperature region, the degree of thecoherency of each orbital channel is different, so strangebehaviors of the conductance can appear.For example, the conductance once increases and thendecreases with temperature decreasing when it is suppressedat T=0 by the interference cancellation between different channels.The interaction effects in the quantum dot systems lead thesensitivities of the conductance to the temperature and tothe gate voltage.
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Kiyohiro Sugiyama, Koichi Kindo, Go Nakamoto, Toshiro Takabatake, Hiro ...
Subject area: Magnetic properties and materials.
1998 Volume 67 Issue 7 Pages
2455-2459
Published: July 01, 1998
Released on J-STAGE: October 01, 1999
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High-field longitudinal magnetoresistance and magnetization measurements up to 36 T have been carried out on a single crystal CeNiSn which shows metallic behavior in the resistivity along the a-axis.Large negative magnetoresistances are found along the a-, b- and c-axes in high fields above 10 T as previously reported in a semiconducting sample.A metamagnetic behaviour in the magnetization is observed along the a-axis at around 15 T.The linear field dependence of log ρ (H) indicates that the Zeeman energy of the 4f-electron moment quenches the pseudo energy gap on the Fermi surface in CeNiSn.
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Noboru Fukushima, Yoshio Kuramoto
Subject area: Magnetic properties and materials.
1998 Volume 67 Issue 7 Pages
2460-2468
Published: July 01, 1998
Released on J-STAGE: October 01, 1999
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Effects of magnetic field on the quadrupolar orderingare investigated with inclusion of fluctuation of order parameters.For the simplest model with the nearest-neighbor quadrupolar interaction, the transition temperature and the specific heat are derived by theuse of the recently proposed effective medium theory.It is shown that magnetic field H has two competing effectson the quadrupolar ordering;one is to encourage the ordering by suppressing the fluctuationamong different components of order parameters, and the other is to block the ordering as in antiferromagnets.The former is found to be of order H^2 and the latter of order H^4.Hence the fluctuation is suppressed for weak fields, and the transition temperature increases with magnetic field.The fluctuation effect is so strong that the entropy released at thequadrupolar ordering is only about a quarter of the full value ln 4 evenwithout the Kondo effect.
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