Volume 67, Issue 1
Displaying 1-50 of 68 articles from this issue
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Hideaki Ujino, Miki Wadati
Subject area: Mathematical methods in physics.
1998 Volume 67 Issue 1 Pages
1-4
Published: January 01, 1998
Released on J-STAGE: October 01, 1999
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We demonstrate an algebraic construction of all the simultaneouseigenfunctions of the conserved operators forthe Calogero model. The eigenfunction is a deformationof the symmetrized number state (bosonic state)of the N decoupled quantum harmonicoscillators. The eigenfunction does not coincide with the Hi-Jackpolynomial, which shows that the conserved operators derived from the numberoperators of the decoupled quantum harmonic oscillators are algebraicallydifferent from those derived by the Dunkl operator formulation.
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Yoshihiko Nonomura
Subject area: Statistical physics and thermodynamics.
1998 Volume 67 Issue 1 Pages
5-7
Published: January 01, 1998
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A new efficient scheme for the finite-size-scaling study of ground-state phase transitions in quantum spin systems is proposed on the basis of the quantum Monte Carlo method. That is, Trotter numbers and simulated temperatures are scaled in accordance with system sizes, and only one simulation is required for each system size. The transition point is estimated independently of the critical exponents using the non-equilibrium relaxation of the order parameter in a very large system. This scheme is confirmed by the estimation of the critical phenomenon of the one-dimensional S=1/2 asymmetric XY model.
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Katsuya Honda
Subject area: Statistical physics and thermodynamics.
1998 Volume 67 Issue 1 Pages
8-11
Published: January 01, 1998
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By removing a trick hidden in the original KPZ paper, a correction in the application of the dynamic renormalization group technique to the KPZ problem is proposed. It is stressed that a fourth derivative term plays an essential role in formulating a consistent scenario. In a one-loop approximation, α =2-z=8(4-d)/(48+4d-d2), is obtained for the roughness exponent α and the dynamic exponent z, which gives reasonable numbers. For 2
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Koji Hukushima, Hajime Takayama, Hajime Yoshino
Subject area: Statistical physics and thermodynamics.
1998 Volume 67 Issue 1 Pages
12-15
Published: January 01, 1998
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The equilibration process ofthe Sherrington--Kirkpatrick spin-glass model is investigated using the exchange Monte Carlo (MC) method.It is found that a MC time scale for equilibration, τ
eq, is nearly proportional to the system size and weakly depends on temperature, in contrast to the thermal activation behavior observed in a conventional MC simulation. Fluctuation of the overlap distribution over samples isconfirmed to follow the non trivial probability law predicted by thereplica-symmetry-breaking theory.
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Naurang L. Saini, Alessandra LANZARA, Antonio Bianconi, Fangcheng Chou ...
Subject area: Structure of liquids and solids; crystallography.
1998 Volume 67 Issue 1 Pages
16-19
Published: January 01, 1998
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We report Cu K-edge extended X-ray absorption fine structure (EXAFS) spectra up to high momentum transfer measured on a superconducting La
2CuO
4.1 single crystal using in-plane polarization of synchrotron light. The EXAFS data with a high signal to noise ratio has enabled the precise determination of the Debye-Waller factors and the pair correlations of Cu--O (planar) and Cu--La pairs of the structurally complex superconducting system. We have observed an anomalous behaviour of the pair correlations at -- 170, K and attributed it to an interplay between temperature-dependent structural modulation of the perovskite and rock-salt layers in the title compound.
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Jun Suda, Hideyuki Chiba, Tsutomu Sato
Subject area: Lattice dynamics and crystal statistics.
1998 Volume 67 Issue 1 Pages
20-22
Published: January 01, 1998
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The first-order Raman frequency shifts of the A
g(2)+B
g(2) mode in a CaWO
4 crystal were measured in the temperature range of 77-- 771K. The frequency shift for this mode changes very slowly with increasing temperature. The temperature dependence of the frequency shift of the A
g(2)+B
g(2) mode was analyzed using the lattice dynamical perturbative treatment. We found that the quartic anharmonic term of the first-order perturbation, as well as the cubic term of the second-order one, and thermal expansion contribute to the temperature dependence of the frequency shift of the A
g(2)+B
g(2) mode in a CaWO
4 crystal.
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Takashi Itoh, Kazuhiko Maeda, Hiroyuki Shibata, Shigeru Tasaka, Masato ...
Subject area: Equations of state, phase equilibria, and phase transitions.
1998 Volume 67 Issue 1 Pages
23-26
Published: January 01, 1998
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Thermal and structural properties of vinylidene fluoride (VDF)-trifluoroethylene (TrFE) copolymers with VDF molar contents between 57 and 77, mol% are examinend by differential scanning calorimetry, X-ray analysis, IR and
19F NMR. It is found from the experimental results that VDF sequences with three or more monomers play an important role in the phase transition and/or phase appearance. Computer simulation for the copolymerization suggests that the copolymer chain of 65--70% VDF contains ca. 50% VDF which is included in the long VDF sequences with three or more monomers. This fraction (50%) is the site-percolation thresh-old for the two-dimensional triangular lattice; transformation from the continuous structural change to the first-order phase transition with the increasing VDF fraction is understood as the percolative phase transition in the two-dimensional crystal system.
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Yoshihiro Ishibashi, Jiri Hlinka
Subject area: Equations of state, phase equilibria, and phase transitions.
1998 Volume 67 Issue 1 Pages
27-28
Published: January 01, 1998
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A simple discrete model is proposed, which reproduces the transition between two commensurate phases with the same modulation period. The transition is of the first order. The model is detailed in the case of the quadruple lattice period.
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Yoshiaki Ono, Ken Deguchi, Tamifusa Matsuura, Yoshihiro Kuroda
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 1 Pages
29-32
Published: January 01, 1998
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Effects of d-site substitution in the d-p model simulating a CuO
2-plane in high-T
c cuprates are investigated using the slave boson technique and the 1/N-expansion method. It is found that nonmagnetic impurities, e.g., Zn, substituted for Cu, strongly scatter the p-holes and drastically decrease hole densities at the neighboring O-sites. In the low doping region, the decrease reduces the Kondo temperature T
K at the neighboring Cu-sites. The repulsion U
pd between holes on the nearest neighbor Cu- and O-sites, which is known to enhance the charge susceptibility in the pure systems without impurities, turns out to promote the reduction of T
K due to the nonmagnetic impurity. Then, Cu d-spins in the vicinity of the impurity behave as local moments at temperatures higher than the reduced T
K.
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Tadao Kasuya
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 1 Pages
33-36
Published: January 01, 1998
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Long-standing anomalies concerning hidden orderings in Ce
xLa
1-xB
6 competing with the Γ
8 quartet Kondo state are solved by introducing single-site dynamical and pair distorted Jahn-Teller effects. The latter is stronger and enhanced by an increased magnetic field. These characteristic Jahn-Teller effects are common in RB
6 and are related to the soft optical R phonon mode and begin at a temperature corresponding to about half of that of the optical R phonon, causing a long tail of specific heat and a strongly frustrated long-range ordering of paired systems, which is expected to be a [1/2, , 1/2, , 1/2] charge dipolar ordering accompanied by the same magnetic dipole ordering, which is particularly enhanced under a magnetic field. This model clearly explains long-standing anomalies in CeB
6, in particular, the anomalous phase diagram and discrepancies between NMR and neutron scattering measurements.
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Hisatomo Harima
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 1 Pages
37-40
Published: January 01, 1998
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Yb
4As
3 has been known as a heavy fermion compound with very low carriers.Recently, polarised neutron measurement has revealed the charge-ordered statein the low temperature phase after a structural phase transition.To clarify the conducting property, a band structure is calculated for hypothetical LuYb
3As
3 where Yb
3+ are replaced with Lu, as it is a nonmagnetic reference material of the charge-ordered state ofYb
3+Yb
32+As
33-.The result shows LuYb
3As
3 to be a semi-metal with As-4p holes andLu-5d electrons, which is consistent with the semi-conducting behaviour of thecharge-ordered state.The Fermi surfaces are located on a plane normal to the Yb
3+ chainwith q = 0.
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Masakazu Murakami, Hidetoshi Fukuyama
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 1 Pages
41-44
Published: January 01, 1998
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Effects of the backward scattering with large momentum transfer areexamined in two-dimensional electron system with a special emphasison electrons around (π, 0), (0, π).The phase diagram is shown in the plane of temperature Tand hole doping δ in the mean field approximation and it is found that d-wave superconductivity, antiferromagnetism and π-triplet pair can coexist near half filling.
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Masatoshi Imada
Subject area: Electronic transport in condensed matter.
1998 Volume 67 Issue 1 Pages
45-48
Published: January 01, 1998
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Small Drude weight D together with small specific heat coefficient γ observed in the ferromagnetic phase of R
1-xA
xMnO
3 (R=La, Pr, Nd, Sm; A=Ca, Sr, Ba) are analyzed in terms of a proximity effect of the Mott insulator. The scaling theory for the metal-insulator transition with the critical enhancement of orbital correlations toward the staggered ordering of two e
g orbitals such as 3x
2-r
2 and 3y
2-r
2 symmetries may lead to the critical exponents of D ∝ δ
u and γ ∝ δ
v with u=3/2 and v=0. The result agrees with the experimental indications.
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G. J. Jin, Z. D. Wang, S. S. Kang, A. Hu
Subject area: Electronic transport in condensed matter.
1998 Volume 67 Issue 1 Pages
49-52
Published: January 01, 1998
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We study electronic transmission and energy spectrain a new kind of Fibonacci quantum waveguide structure proposedby us. The importance of commensurability of the length parameters indetermining electronic behaviors is pointed out for the first time. Self-similarity and six-cycle in the transmission spectraare clearly seen. It is suggested that the quasi-periodic property ofelectronic transport related to the Landauer-Büttiker conductance is experimentally observable in this kind of structure.
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Masahiko Hiroi, Shin–ichiro Kobayashi, Masafumi Sera, Norio Koba ...
Subject area: Electronic transport in condensed matter.
1998 Volume 67 Issue 1 Pages
53-56
Published: January 01, 1998
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We have studied the magnetoresistance and magnetic phase diagram of Ce
xLa
1-xB
6(x = 0.65, 0.7). The antiferromagnetic (AF) phase IV recently discovered in Ce
0.75La
0.25B
6, where it exists only in a narrow temperature and magnetic field region, extends down to T = 0 K for x = 0.7. The magnetoresistance in phase IV is much smaller than that in the AF phase III dominated by the antiferro-quadrupolar (AFQ) ordering. A first-order phase transition takes place at a critical magnetic field from phase IV to III and that field for H // ‹ 100 › is smaller than that for H // ‹ 110 ›. These can be explained by considering the difference of the free energy in magnetic fields between phases IV and III. A tetra-critical point seems to exist for x = 0.75 but it is separated into two tri-critical points by the IV-II boundary for H // ‹ 110 › in Ce
0.65La
0.35B
6.
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Katsuaki Kodama, Toshihiko Fukamachi, Hiroshi Harashina, Masaki Kanada ...
Subject area: Magnetic properties and materials.
1998 Volume 67 Issue 1 Pages
57-60
Published: January 01, 1998
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The magnetic properties of two polymorphs of CuNb
2O
6 with quasi-one-dimensional zig-zag spin (S=1/2) chains of Cu
2+ ions are studied. The magnetic excitation spectra of Cu spins measured by neutron scattering, and the T-dependence of the longitudinal spin relaxation rate of
93Nb nuclei by NMR indicate the existence of the spin gap in the monoclinic phase whose magnitude is consistent with the one deduced by the detailed analyses of uniform magnetic susceptibility at low temperatures. The behavior in the monoclinic phase is in clear contrast to that found in the orthorhombic phase.
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Hiroaki Kusunose
Subject area: Magnetic properties and materials.
1998 Volume 67 Issue 1 Pages
61-64
Published: January 01, 1998
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Ground-state properties are examined for an extended two-channel Kondomodel where the Hilbert space of the localized states is extended to include a singlet state in addition to thedoublet states.By means of zero-th order variational wavefunctions with differentsymmetries, which are associated with the non-Fermi-liquid and theFermi-liquid ground states, we demonstrate that the channel exchange coupling via the localized singlet statestabilizes the Fermi-liquid wavefunction. The ground-state phase diagrams, which are in qualitative agreement with theprevious study performed by Koga and Shiba, are obtained.The comparison to the structure of the resultant wavefunctions suggests thata unique non-Fermi-liquid (Fermi-liquid) fixed point exists, irrespective ofthe localized ground state.
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Kenji Ikushima, Hiroshi Yasuoka, Satoshi Tsutsui, Masakatsu Saeki, Sab ...
Subject area: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1998 Volume 67 Issue 1 Pages
65-66
Published: January 01, 1998
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The
235U (I=7/2) NMR for magnetic uranium sites with 5f-electronshas been first observed in the antiferromagnetic state of UO
2.The hyperfine field is estimated to be 252.3 ± 0.5 T.Well articulated quadrupole splittings have also been observedwith |e
2qQ(3cos
2θ-1)/h| = 392 ± 11 MHz. This indicates the presence of an electric field gradient produced by the Γ
5-ground state for 5f-electrons in the magnetic ordering.
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Taizo Masumi, Hiroyuki Yamaguchi, Takayuki Ito, Hiroyasu Shimoyama
Subject area: Optical properties and condensedmatter spectroscopy and other interactions of matter with particles and radiation.
1998 Volume 67 Issue 1 Pages
67-70
Published: January 01, 1998
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By using CuO crystals prepared with the floating zone technique, we have observed for the first time an emergence of new fine structures with an energy splitting of 5.86 meV in the optical absorption spectra κ(T, ν) near the fundamental absorption edge, E
G-- 1.60 eV, below 90 K. These results are ascribable either to [1] the direct allowed n = 1 exciton transitions below 90 K at the absorption edge, or [2] the transition due to magnetically ordered localized states such as spin-canted weak ferromagnetic states with a possible splitting due to the exchange interaction E
ex=5.86 meV in the hybridized Cu(3d)O(2p) valence electronic system of antiferromagnetic semiconductor CuO.
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Juan García–Escudero
Subject area: Mathematical methods in physics.
1998 Volume 67 Issue 1 Pages
71-77
Published: January 01, 1998
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Selfsimilar planar patterns with nine-fold and fifteen-fold symmetries are generated with the help of a construction that can be extended to odd symmetries higher than five. Generic atomic decorations of the patterns have Bragg spectrum and therefore they can be used as structure models of quasicrystals.
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Kazuhiro Hikami, Yasushi Komori
Subject area: Mathematical methods in physics.
1998 Volume 67 Issue 1 Pages
78-82
Published: January 01, 1998
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Integrable boundary Boltzmann weight for the eight-vertexsolid-on-solid model is constructed.Based on the operator-valued solutions of both the Yang-Baxterequation and the reflection equation, we propose a simple method to give the Boltzmann weight using thevertex-IRF correspondence.
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Narimasa Sasa, Yasuhiro Ohta, Junta Matsukidaira
Subject area: Mathematical methods in physics.
1998 Volume 67 Issue 1 Pages
83-86
Published: January 01, 1998
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We apply Hirota's bilinear form approach to the analysis ofthe SU(2) self-dual Yang-Mills equations.Solutions of the bilinear forms are represented by usingthe Toda-molecule type determinants with new linear dispersion relations.We also discuss dimensional reductions of the bilinear formsand the (2+1)-dimensional integrable equations derived from them.These integrable equations are higher dimensional extension ofthe nonlinear Schröinger equation and the derivativenonlinear Schrödinger equation.
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Rei Inoue, Kazuhiro Hikami
Subject area: Classical and quantum physics: mechanics and fields.
1998 Volume 67 Issue 1 Pages
87-92
Published: January 01, 1998
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An extension of the Lotka-Volterra model, which we call the hungry-Volterramodel or the Bogoyavlensky lattice, is studied. We show that the model is integrable in both classical and quantum levels by use of the local Lax matrix.The relationship between the Lotka-Volterra model andsome integrable systems is briefly discussed.
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Takeya Tsurumi, Miki Wadati
Subject area: Classical and quantum physics: mechanics and fields.
1998 Volume 67 Issue 1 Pages
93-95
Published: January 01, 1998
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By generalizing the Zakharov's theory for collapses of Langmuir waves, we investigate the instabilities of wavefunctions in the D-dimensionalN-component coupled nonlinear Schrödinger equations under harmonicpotentials. We show that all wavefunctions surely collapse in a finite time, when the total energy is negative.For a special case that D=2 and all coefficients of harmonicpotential terms are equal, we predict that the collapse can occur even when some fields interact repulsively.
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Hidetsugu Sakaguchi
Subject area: Statistical physics and thermodynamics.
1998 Volume 67 Issue 1 Pages
96-98
Published: January 01, 1998
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A coupled map lattice model is proposed to perform asimulation for growth patterns in a diffusion field.An additional variable corresponding to an order parameter is introduced, and the time evolution of the order parameter variable obeys an absorption rule at the interface.Various types of morphology including the DLA-like pattern are obtained by changing the boundary conditionsand the absorption rule.
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Norio Inui, Norio Konno, Genichi Komatsu, Koichi Kameoka
Subject area: Statistical physics and thermodynamics.
1998 Volume 67 Issue 1 Pages
99-102
Published: January 01, 1998
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Using the series expansion method and Monte Carlo simulation, we study the directed percolation probability on the square lattice V
n0= { (x, y) ∈ Z
2:x+y=even, 0 ≤ y ≤ n, - y ≤ x ≤ y }.We calculate the local percolationprobability P
nl defined as the connection probability between theorigin and a site (0, n). The critical behavior of P
∞lis clearly different from the global percolation probability P
∞g characterized by a critical exponent β
g.An analysis based on the Padé approximants shows β
l=2β
g.In addition, we find that the series expansion of P
2nl can be expressed as a function of P
ng.
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Minoru Yoshimoto, Tomohiko Yamaguchi, Hitoshi Sato, Koichi Kato, Hitos ...
Subject area: Statistical physics and thermodynamics.
1998 Volume 67 Issue 1 Pages
103-111
Published: January 01, 1998
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We investigate systematically the effect of Gaussian white noise (type P noise) on the low flow rate chaos in both systems far from and close to bifurcation points using the three-variables ODE of the Belousov-Zhabotinsky reaction developed by Györgyi and Field. When the noise is added to the chaos with the bifurcation parameter far from bifurcation points, the chaos trajectories are slightly scattered. However, in the chaos having the bifurcation parameter near bifurcation points, it happens that topological entropy is constant but the Lyapunov exponent decreases. We have found that this phenomenon, named “noise-induced order”, appears in intermittent chaos with the internal structure of m-periodic oscillation, and that “noise-induced order” is caused by an increase in the length of laminar region and the subsequent change of the invariant density.
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Koh Wada, Yoshihiro Ogawa
Subject area: Statistical physics and thermodynamics.
1998 Volume 67 Issue 1 Pages
112-118
Published: January 01, 1998
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The cluster variation method (CVM) in the cactus approximation is applied to a pseudo-spin Ising Hamiltonian of the Slater-Takagi model for KD
2PO
4-type hydrogen-bonded ferroelectrics to calculate the wave-number dependent susceptibility χ(q), mainly focussing on the ferroelectric phase.The strong anisotropy of polarization fluctuations along the easy z-axis is shown to appear not only in the paraelectric phase but also in the ferroelectric phase when the ice-rule limit is approached. An analytical expression of the spontaneous polarization is fully utilized for calculations on χ(q) below the transition temperature.
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Hideaki Ujino, Takayuki Tsuchida, Miki Wadati
Subject area: Statistical physics and thermodynamics.
1998 Volume 67 Issue 1 Pages
119-123
Published: January 01, 1998
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Exact treatment of the microcanonical ensemble forthe quantum Calogero model is presented through the exclusion statistical thermodynamic Bethe ansatz (TBA) method.All the virial coefficients for the modelin the thermodynamic limit are rigorously calculated, which arein agreement with the conjectured results.
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Pallath Chandran, Nirmal C. Sacheti, Ashok K. Singh
Subject area: Fluid dynamics.
1998 Volume 67 Issue 1 Pages
124-129
Published: January 01, 1998
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The effects of viscosity, magnetic field and buoyancy force on the unsteady free convection flow of an incompressible and electrically conducting fluid have been analysed when the flow is generated by uniformly accelerated motion of a vertical plate subject to constant heat flux. The resulting boundary value problem has been solved exactly for the temperature and velocity variables. The fluid velocity and the skin friction have been computed for some saturated liquids and the effects of the fluid and external forces have been discussed. It is observed that the increase in velocity caused by the larger heat flux can be controlled by enhancing the magnetic field strength. The skin friction at the boundary increases for larger Prandtl and Hartmann numbers, and decreases with increasing Grashof number.
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Jiro Mizushima, Shinichiro Yanase, Taku Yoshizawa
Subject area: Fluid dynamics.
1998 Volume 67 Issue 1 Pages
130-139
Published: January 01, 1998
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Stability of the flow in a curved channel is investigated with the Dean approximation by using the weakly nonlinear stability theory. A set of amplitude equations for the Dean vortices of wavenumber ratio 1:2 is derived. The amplitude equations describe the resonant interactions between the fundamental mode and the higher harmonic. The equilibrium amplitudes of the Dean vortices are evaluated from the set of amplitude equations numerically. It is concluded that the phenomena of the coalescence of two vortices and the splitting of one large vortex into two are explained from the 1:2 resonance.
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Takashi Kanki, Masayoshi Nagata, Tadao Uyama, Soichiro Ikuno, Atsushi ...
Subject area: The physics of plasmas and electric discharges.
1998 Volume 67 Issue 1 Pages
140-146
Published: January 01, 1998
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In the flux amplification compact torus experiment, the bias flux penetrates the wall of the flux conserver because it has been switched on a suitably long time prior to the production of a seed spheromak. The magnetohydrodynamic equilibrium configurations with a non-constant λ (≡ μ
0j · B/ |B|
2 ) profile of a helicity-driven spheromak incorporating the situation of the bias-flux leakage out of the flux conserver are numerically determined by using the novel combination of the finite difference and the boundary element method. Here μ
0, j and B are the permeability of vacuum, the current density and the magnetic field, respectively. The results of computations show that the effects of the bias-flux leakage cause a slight rise of the entire safety factor q in the case of I
C /I
P=0.4 (I
C and I
P denote the total current of coil and plasma, respectively) because of the decrease in poloidal field over all space. Then, they also give rise to a 22.0% decrease in the magnetic flux inside the separatrix.
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Ryoji Hiwatari, Yuichi Ogawa, Tsuneo Amano, Tomonori Takizuka, Hiroshi ...
Subject area: The physics of plasmas and electric discharges.
1998 Volume 67 Issue 1 Pages
147-157
Published: January 01, 1998
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To study the confinement characteristics of dimensionally similardischarges (ρ
* experiments) in JT-60U L-mode plasmas, transport simulations have been carried out with three different transport models; i.e., theBohm-type, the Current-Diffusive-Ballooning-Mode and the Multi-Mode models. For all models the electron temperature is in good agreement (within 15% in the electron stored energy). If the thermal diffusivity of ions isaround two times of that of electrons, it seems that the simulation resultscould reproduce the experimental ion temperature. We have compared diffusion coefficients to study the characteristics of the ρ
* scaling ofeach transport model. In the Bohm-type model it is found that thesimulation results yield the Weak-Gyro-Bohm characteristics for electronsand ions, even though the Bohm-type thermal diffusivity is incorporated. This can be accounted for by the factor q
2/L
T* in the diffusioncoefficient. In the CDBM model, the simulationresults clearly show the Gyro-Bohm characteristics. In the Multi-Modemodel, Gyro-Bohm characteristics is predicted in the simulationresults. Since experimental results have exhibited Weak-Gyro-Bohmcharacteristics, we could conclude that the Bohm-type model which has beenempirically developed in JET L-mode plasmas might be applicable for JT-60UL-mode plasmas, as well, from the viewpoints not only of the absolute valueof plasma temperatures but also of ρ
* scaling.
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Itsuo Ishikawa, Satoru Iizuka, Rikizo Hatakeyama, Noriyoshi Sato
Subject area: The physics of plasmas and electric discharges.
1998 Volume 67 Issue 1 Pages
158-162
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A plasma with negative ions (negative ion plasma), which is generated by introducing a small amount of SF
6 gas into a surface ionized plasma (e.g., Q-machine plasma), is investigated by electrostatic probe measurements. A theoretical analysis has been made by considering the presence of a negative ion sheath (NIS) in addition to the usual positive ion sheath (PIS), where the thermal velocity of negative ions is less than that of positive ions and the electron number density n
e is much less than the positive ion n
+. The ratios of saturation current of electrons and negative ions to that of positive ions, which are experimentally obtained by probe measurements, suggest that the sheath has a property of the change from PIS to NIS at the ratio of electron to positive-ion number densities n
e/n
+ below 10
-2.
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Roberto A. Clemente, Massimo Tessarotto
Subject area: The physics of plasmas and electric discharges.
1998 Volume 67 Issue 1 Pages
163-165
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A new class of magnetic fields, deduced from the extension of force-free fields to the complex domain, is presented. The compatibility of such kind of fields with the magnetic diffusion equation for harmonic fields, in absence of plasma flow velocity, is shown. This allows to produce a static Lorentz force density in a resistive plasma and possibly to balance pressure forces in the momentum equation. An explicit example of equilibrium solution for a cylindrical plasma column with scalar pressure is presented and its connections with previous experimental results are discussed. Some discussion is also devoted to the question of the existence of this kind of closed equilibria.
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Yuichi Yatsuyanagi, Tadatsugu Hatori, Tomokazu Kato
Subject area: The physics of plasmas and electric discharges.
1998 Volume 67 Issue 1 Pages
166-175
Published: January 01, 1998
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Motion of the vortex-current filaments is examined via cutoff Biot-Savart numerical MHDsimulations of single and double filaments.We have introduced a vortex-current filament by analogy with the vortex filament.The vortex-current filament consists of electric current density and vorticitywhich are parallel to the axis of the filament.Attention is needed to demonstrate the difference between vortex andvortex-current filaments.In this paper we present two numerical results of vortex-current filament motion, using cutoff Biot-Savart method.In the limit of no electric current, the two results are in goodagreement with vortex filament systems.The first result is obtained for two circular ring filaments.Here we find there are some cases where the qualitative characteristics of the motionare unchanged by introducing electric current along the vorticity.On the other hand, the period of the mutual slipping motion of the filaments is changed.The second result is related to oscillation of an elliptic ring filamentwhich is well known phenomenon of the “pure” vortex filament.It is remarkable that the period of oscillation becomes infinite at a criticalelectric current inside the filament.
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Shinji Nakazawa, Yukiharu Ohsawa
Subject area: The physics of plasmas and electric discharges.
1998 Volume 67 Issue 1 Pages
176-185
Published: January 01, 1998
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Ion motions in shock waves propagating perpendicular to a magnetic field are studied through theory and simulation; the shocks with relativistic propagation speeds are considered. In such shocks the longitudinal electric fields are less important than in nonrelativistic ones. From the analysis of ion orbits it is found that ion velocities parallel to the wave front can be comparable to the shock propagation speed v
sh in the pulse region. Expressions for ion energies, which can be relativistic, are given as a function of the shock propagation speed. Then, simulations of shock waves are performed by use of a one-dimensional, relativistic, electromagnetic particle code with full ion and electron dynamics. The shock speeds in the simulations were in the range 0.5 ≤ v
sh / c ≤ 0.9. The simulation results on ion orbits and energies are compared in detail with the theory.
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Yusuke Wakabayashi, Nobuyoshi Wakabayashi, Noritaka Kuroda, Masato Nis ...
Subject area: Structure of liquids and solids; crystallography.
1998 Volume 67 Issue 1 Pages
186-191
Published: January 01, 1998
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X-ray diffraction and optical absorption measurements were carried out on single crystals of [Pt(en)
2][Pt(en)
2Cl
2](BF
4)
4 (en = etylenediamine). This compound has a quasi-one dimensional structure with alternating (II and IV) Pt valences along the c-axis. An orthorhombic to monoclinic structural phase transition occurs around 255 K and the charge-transfer absorption edge was found to have a sudden shift at the transition. X-ray diffuse scattering was observed around (0 0 2n + 1) reciprocal points. While optical spectra were affected by irradiating the sample with blue light, the X-ray diffraction intensity did not change either by irradiation or by varying the sample temperature. We attribute the diffuse scattering to solitons produced during crystal growth. From measurements of thermal diffuse scattering, limited information about the phonon dispersion relation was obtained.
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Souichirou Tanimori, Shuji Shimamura
Subject area: Mechanical and acoustical properties of condesed matter.
1998 Volume 67 Issue 1 Pages
192-197
Published: January 01, 1998
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The electronic response to lattice displacement in a transition metal, Pd and a noble metal, Ag has been studied theoretically by means of electronic structure calculations.The fcc lattice of these metals has been periodically cleaved or slipped on the (111) planes; the slip direction is [\bar{1}10].The electronic structure calculations in the cleaved and slipped lattices have been carried out by using the tight binding method which reproduces first-principles band structure calculations for the fcc lattice.It is shown that the electronic response to lattice displacement is dominated by d electrons for Pd and by s-p electrons for Ag.In consequence, both cleaving and slipping increase the electron energy of Pd relative to that of Ag.In other words, electrons in Pd have a higher resistance to lattice displacement than those in Ag.The calculated results are discussed in connection with the electronic origin of hydrogen embrittlement in Pd.
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Mamoru Yamashita
Subject area: Equations of state, phase equilibria, and phase transitions.
1998 Volume 67 Issue 1 Pages
198-203
Published: January 01, 1998
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The Ising model and the classical XY model with frustrating second nearest neighbour interaction in an axial direction have qualitatively different properties to each other both at ground state and in the finite temperature. The XY model exposed to the symmetry breaking field with twofold symmetry is here introduced, which is reduced to the Ising model, that is, the ANNNI model in the limit of the strong field strength. The ground state of this model is examined, in which the freedom of the XY spin is shown to be suppressed at rather small strength of the symmetry breaking field and accordingly the Ising properties dominate in large area on an interaction parameter versus field diagram, while the freedom of XY spin survives only at an area with weak field. This result seems to explain why the successive phase transitions observed in ferro- and antiferro-electric smectic liquid crystals can occur.
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Akihiko Matsuyama, Tadaya Kato
Subject area: Equations of state, phase equilibria, and phase transitions.
1998 Volume 67 Issue 1 Pages
204-209
Published: January 01, 1998
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A theory is introduced to describe phase separations in solutions of end-to-end aggregates which are formed by intermolecuar physical bonding between rodlike molecules. In these solutions we have three different phase transitions:self-associations, phase separations and molecularorientations. On the basis of the Flory-Abe theory for polydisperse systems of rodlike particles, we examine the equilibriumsolution properties. By using themultiple-chemical equilibrium conditions for the molecularassociations, we derive the size distribution of theend-to-end aggregates in an isotropic and in a nematicphase. We show that the end-to-end aggregates cause an nematic-isotropic phase transition as well as the new types of phase separations. For various values of the association constant, we calculate phase diagrams in the temperature-concentration plane.
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Hiroshi Furukawa
Subject area: Equations of state, phase equilibria, and phase transitions.
1998 Volume 67 Issue 1 Pages
210-215
Published: January 01, 1998
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The local equilibrium assumption and the general nonlinear transformationof the order parameter in the phase ordering dynamics are discussed. By this method we can relate the kinetic equation similar to that of Kawasaki, Yalabic and Gunton (KYG) with that of Ohta, Jasnow and Kawasaki (OJK). The discussionis done both for the scalor and vector field order parameter.
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Takafumi Kita
Subject area: Quantum fuids and solids: liquid and solid helium.
1998 Volume 67 Issue 1 Pages
216-224
Published: January 01, 1998
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With proper care on the boundary conditions, the total orbital angular momentum L
z at finite temperatures is microscopically calculatedfor the Anderson-Brinkman-Morel state in a cylinder with axial symmetry about the z axis, i.e. the textures considered by McClure and Takagi at T=0.The pairing in this geometry occurs between m and 1-m one-particle states, where m denotes the axial quantum number.It is found that L
z decreases from its zero temperature value \frac{(h/2π)}{2} N, with N the total particle number, in the same way asthe components of the superfluid density tensor.Responsible for this reduction is identified to be the phase shift between m and 1-m quasiparticle states caused by the difference in the centrifugal potentials.This fact implies that the plane-wave representation is not suitable for the problem.
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Fumitaka Arai, Shin–ichi Kimura, Mikihiko Ikezawa
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 1 Pages
225-229
Published: January 01, 1998
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Electronic structures of ten kinds of rare-earth sesquioxide single crystals (R
2O
3; R=La, Pr, Nd, Sm, Eu, Gd, Er, Tm, Yb and Lu) were investigated by 4d-4f resonant photoemission measurement. The information of the electronic structure, especially the relative binding energy of 4f state and O 2p valence band, was obtained. The 4d-4f resonant photoemission spectra of valence band can be explained by multiplet structure of 4f
n-1 final state and the mixing between 4f and O 2p. The O 2p valence band has 4d-4f resonance in La
2O
3 that is in a typical 4f
0 case. La 5d character is considered to mix to the O 2p valence band.
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Jinliang Wang, Masaaki Hirai, Masahiko Kusaka, Motohiro Iwami
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 1 Pages
230-233
Published: January 01, 1998
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Electronic states of manganese silicides with the composition of MnSi or MnSi
1.7 were investigated by soft X-ray emission spectroscopy. The formation of MnSi and MnSi
1.7 with single phase was identified by X-ray diffraction. Si-K
β and Si-L
2, 3 emission-band spectra were measured, where the Si-K
β reflects the valence-band density of states with p-symmetry and the latter reflects the one with s- and/or d-symmetry. The spectrum of Si-L
2, 3 for MnSi
1.7 was different from that of MnSi. The origin of this difference is discussed in comparison with those of other silicides.
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Hisashi Kondo, Tohru Moriya
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 1 Pages
234-241
Published: January 01, 1998
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Antiferromagnetic and metal to insulator transitions in the ground state of two-dimensional half-filledand nearly half-filled Hubbard models with the nearest neighbor and the second nearest neighbor transfers (-t and t
′, respectively) are studied by using the Green's function approach with the self-energy up to the second order in the coupling constant U.For a choice of the parameter value t
′/t=0.2the half-filled model undergoes the first order phase transition between paramagnetic metallic (PM) phase and antiferromagnetic insulator (AFI) phase at U/t=4.0 while the first order transition between PM and antiferromagnetic metallic (AFM) phases takes place for nearlyhalf-filled band. The one-electron spectral density is calculated for the PM, AFM, and AFI phases near the phase boundaries. In the PM phase the quasi-particle dispersion indicates the bandnarrowing from the Hartree-Fock results and the flat band behavior as wasindicated by previous stadies and was observed in high-T
c cuprates. The quasi-particle dispersion in the AFM phase is seen to be close to the Hartree-Fock results.
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Hideaki Maebashi, Hidetoshi Fukuyama
Subject area: Electronic transport in condensed matter.
1998 Volume 67 Issue 1 Pages
242-251
Published: January 01, 1998
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The electrical resistivity due only to mutual Coulomb interactionof the d-dimensional lattice electron systems (d≥ 2)in the presence of Umklapp scattering processesis studied on the basis of the Fermi liquid theory.It is shown that normal scattering processes generally contribute to the resistivity if Umklapp scattering processes are present.This fact gives a natural explanationof the resistivity of the d=∞ Hubbard modelwhich is determined only bythe damping rate of quasi-particles, γ.In the case of d=2, however, it is shown that the resistivityis proportional to T
2, T being the temperature, even when normal scattering processes, which give T
2 log T-contribution to γ, contribute to the resistivity.In the special case of the square lattice, where the transfer integrals are only between the nearest neighbors, the coefficient of the T
2-term in the second order of the interaction is shown to diverge as (1/δ ) log (1 / δ ) when δ → 0, δ being the doping rate away from half-filling.
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Masahiko Ichimura, Akimasa Sakuma, Yoshimasa Murayama
Subject area: Electronic structure and electrical properties of surfaces, interfaces and thin films.
1998 Volume 67 Issue 1 Pages
252-254
Published: January 01, 1998
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The spin polarization of the finite-size systems consisting ofFe monolayer and Au layers in Fe/Au(n) (n=2--12) with [001] stacking is studied by the self-consistent band calculation. At Au surface layer the magnetic moment decreases exponentially with 6 monolayer thickness with increasing number of Au layers. The decreasing behavior of the inside Au layers is quite different with that of the surface layer. With increasing number of Au layers the moment of Fe monolayer changes non-monotonically with size of 0.1μ
B.
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R. Y. Gu, Z. D. Wang, D. Y. Xing
Subject area: Electronic structure and electrical properties of surfaces, interfaces and thin films.
1998 Volume 67 Issue 1 Pages
255-258
Published: January 01, 1998
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The inverse giant magnetoresistance (MR) effect for current in plane (CIP) and current perpendicular to plane (CPP) geometries is studied by using a semiclassical approach. Interestingly, we find that, besides that the inverse/normal MR can occur in both CIP and CPP cases, it is also possible that the inverse MR effect appears only in one of them. We attribute this phenomenon to the different roles of interface and bulk scatterings in these two cases: the interface scattering is more important for CIP-MR than for CPP-MR while the bulk scattering is the opposite.
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Ming–Fa Lin, Der–San Chuu
Subject area: Electronic structure and electrical properties of surfaces, interfaces and thin films.
1998 Volume 67 Issue 1 Pages
259-263
Published: January 01, 1998
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Toroidal carbon nanotubes (TCN's) are threaded by magnetic flux (φ ). The magneto-electronic structures are studied within the tight-binding model. The curvature effect, which is due to the misorientation of the π -electron orbitals, might play an important role on the low energy electronic states. The thin TCN's, with armchair-zigzag and zigzag-armchair structures, exhibit four (three) types of energy gaps in the presence (absence) of the curvature effect. The magnetoelectronic structures clearly vary with φ except the thin zigzag-armchair TCN's. They could exhibit the periodical Aharonov-Bohm oscillations, since the Zeeman splitting is generally negligible except at large φ 's.
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