-
Satoshi Sawai, Yoji Aizawa
Subject area: Statistical physics and thermodynamics.
1998 Volume 67 Issue 8 Pages
2557-2560
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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A simple coupled oscillator system with chemotaxis is introducedto study morphogenesis of cellular slime molds. The modelsuccessfuly explains the migration of pseudoplasmodium which hasbeen experimentally predicted to be lead by cells with higherintrinsic frequencies. Results obtained predict that its velocityattains its maximum value in the interface region between totallocking and partial locking and also suggest possible rolesplayed by partial synchrony during multicellular development.
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Gongwen Peng, Takao Ohta
Subject area: Statistical physics and thermodynamics.
1998 Volume 67 Issue 8 Pages
2561-2564
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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We study a two-dimensional granular system by computer simulationswhere each particle's velocity is perturbed by random noiseinstantaneously after every time period. We find that both the densityand velocity correlations are long ranged with a power-lawscaling form. Energy dissipation in a single collision is also foundto satisfy a power-law distribution.
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Hiroshi Orihara, Yoshinobu Sato, Tomoyuki Nagaya, Yoshihiro Ishibashi
Subject area: Measurement science, general laboratory techniques, and instrumentation systems.
1998 Volume 67 Issue 8 Pages
2565-2567
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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The orientational fluctuations in a smectic liquid crystal were successfully observed with a high-speed video camera. From the series of images obtained, first the spatial Fourier transformation of each image was computed and then the time correlation function at each wave number was calculated. It was found that the time correlation function shows an exponential decay and the inverse of the relaxation time is proportional to the square of the wave number. The ratio of the elastic constant to the viscosity was also obtained in this experiment.
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G. Kim, A. V. Khugaev, Il–Tong Cheon
Subject area: Nuclear reactions and scattering: specific reactions.
1998 Volume 67 Issue 8 Pages
2568-2570
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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Analyses of experimental data on the elastic scattering of protons with energy of 1 GeV on
12C and
13C nuclei have been carried out by taking a single-particle 2p state of
13C.
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Masaki Sakurai, Koji Watanabe, Kenji Sumiyama, Kenji Suzuki
Subject area: Studies of special atoms and molecules.
1998 Volume 67 Issue 8 Pages
2571-2573
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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We have tried to produce free iron clusters using a laser vaporization source. The cluster beam intensities of Fe
n with n=13, 15, 19 and 23 measured using a time-of-flight mass spectrometer are higher than those of neighboring size clusters for both autoionized and postionized conditions, i.e., there are magic numbers in the iron clusters. These magic numbers can be related to the icosahedral and bcc structure units and to the existence of iron cluster isomers.
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Naoki Katsuragawa, Hitoshi Hojo, Atsushi Mase
Subject area: The physics of plasmas and electric discharges.
1998 Volume 67 Issue 8 Pages
2574-2577
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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Computational study on the cross polarization scattering of ultrashort-pulse electromagnetic waves produced by magnetic fluctuations is presented. One-dimensional coupled wave equations for ordinary and extraordinary modes are solved for incident unipolar subcycle pulses in an inhomogeneous magnetized plasma. It is shown that the peak frequencies in the spectral signals of the mode-converted reflected waves are determined from the Bragg resonance condition in the wave numbers of the ordinary mode, the extraordinary mode and the magnetic fluctuations for relatively short-wavelength localized magnetic fluctuations.
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Koh Saitoh, Kenji Tsuda, Michiyoshi Tanaka
Subject area: Structure of liquids and solids; crystallography.
1998 Volume 67 Issue 8 Pages
2578-2581
Published: August 01, 1998
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A new structural model of an Al
72Ni
20Co
8 decagonalquasicrystal is constructed on the basis of high-angle annular dark-fieldimages and high-resolution electron microscope images.The model is composed of two types of atom clusters with about a 0.4, nmradius as basic structural units, which are similar to the unit existing inthe Al
13Fe
4 monoclinic approximant.The two clusters are located at the lattice points of the rhombic Penroselattice.The model satisfies the symmetry of space group P10
5/mmc.High-resolution electron microscope images calculated from the model agreewell with the experimental ones.
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Hiroyuki Fujishiro, Tetsuo Fukase, Manabu Ikebe
Subject area: Mechanical and acoustical properties of condesed matter.
1998 Volume 67 Issue 8 Pages
2582-2585
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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The electrical resistivity, magnetization, dilatation and sound velocity have been measured for La
1-XSr
XMnO
3 (0.48≤ X≤ 0.90) polycrystals. Observed anomalies in the sound velocity and the dilatation strongly suggest the occurrence of the charge ordering within the Sr concentration range 0.48≤ X≤ 0.82. A phase diagram of the charge-ordered state in La
1-XSr
XMnO
3 as a function of temperature T and the Sr concentration X is proposed.
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Hiroshi Matsui, Masanori Yamaguchi, Satoshi Endo, Tomoaki Inuzuka, Hir ...
Subject area: Mechanical and acoustical properties of condesed matter.
1998 Volume 67 Issue 8 Pages
2586-2589
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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Longitudinal sound velocity measurements propagating along the interlayer direction have been performed at 53.4 MHz by a phase comparison method on a quasi-two-dimensional (Q2D) organic superconductor α-(BEDT-TTF)
2NH
4Hg(SCN)
4 with T
c = 1 K. Temperature dependence of the sound velocity shows anomalies around 20 K and 60 K. The acoustic de Haas-van Alphen (dHvA) effects are observed below 1.8 K for the first time in these organic metals. The quantum oscillations originate from the α-Fermi surface (FS) of a weakly warped cylindrical shape. According to the theoretical formulations by Kataoka and Goto for an acoustic dHvA effect, the absolute area coefficient | Λ
L | is estimated to be about 3.5. The multiband term Λ
Lm is concluded to dominantly contribute to | Λ
L |.
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Jun–ichiro Kishine, Kenji Yonemitsu
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 8 Pages
2590-2593
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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Effects of the intrachain electron-electron umklapp process and theinterchain one-particle hopping, t
⊥, in a weakly coupledhalf-filled chain system have been studied, based on the perturbativerenormalization-group approach.By solving the scaling equations, we found that the intrachain umklappprocess strongly suppresses an interchain one-particle process and causes a finite critical value for t
⊥, t
⊥c. Fort
⊥⊥ c, as the temperature decreases, the system undergoes a phase transition into an antiferromagnetic long-range-ordered phase at a transitiontemperature TN which increases with the increasing t⊥. On the other hand, for t⊥>t⊥ c, the system undergoes acrossover to the Fermi liquid phasewhere the interchain coherent propagation of quasi-particles occurs.
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Shingo Tanaka, Hisatomo Harima
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 8 Pages
2594-2597
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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An FLAPW electronic structure and Fermi surfaces are calculated for YCo
2.Mass enhancement factor is also calculated based on the Fermi liquid theory.Investigations are performed by treating the Fermi energy as a parameteraccording to a previous study.Reasonable mass enhancement is obtained by assuming the Fermi liquidtheory resulting in a reasonable range of values of U
dd for Co-d electrons.The same calculation for CeCo
2 reveals that CeCo
2 is a differentmagnetic system.
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Satoshi Nishimoto, Yukinori Ohta
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 8 Pages
2598-2601
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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An exact-diagonalization technique on small clusters is used to study the ground state of the dimerized t-J model at quarter-filling. The equal-time charge and spin correlations, charge and spin gaps, and binding energy are calculated for the two-dimensional lattice with a spatial dimerization pattern corresponding to organic conductors κ-(BEDT-TTF)
2X. We show that competition between the effects of two types of dimerization, i.e., dimerization in the hopping integral and dimerization in the exchange interaction, leads to the insulator-superconductor transition in the ground state of the model. The phase diagram is thereby presented.
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Hitoshi Seo, Hidetoshi Fukuyama
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 8 Pages
2602-2605
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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A possible ground state of NaV
2O
5 is proposedbased on the Hartree approximation for both on-site and intersite Coulomb interactions. The results indicate that the intersite Coulomb interaction induces a zigzag type of charge disproportionation (i.e., charge ordering) along the ladders of V ions, resulting in localized spins between neighboring ladders to form a spin gap. This new state, which is different from the spin-Peierls state so far believed, seems to be consistent with the existing experimental results.
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Masaru Onoda, Ikuo Ichinose, Tetsuo Matsui
Subject area: Electronic transport in condensed matter.
1998 Volume 67 Issue 8 Pages
2606-2609
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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Being motivated by recent experimental data on YBaCuO, we calculate the dc resistivity ρ in the spin-gap state of the charge-spin-separated t-J model using a massive gauge theoryof holons and spinons. The result shows that ρ(T) deviates downward from the T-linear behavior below the spin-gap onset temperature T
* as ρ(T) ∝ T {1 -c(T
*-T)
d}, where the mean field value of d is 1/2.To achieve smooth deviation from the T-linear behavior, d > 1 is required. The deviation reduces with increasing hole doping.
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Takenobu Yoshino, Toshiro Takabatake, Masafumi Sera, Masahiko Hiroi, N ...
Subject area: Electronic transport in condensed matter.
1998 Volume 67 Issue 8 Pages
2610-2613
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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We report the high-field magnetization and longitudinal magnetoresistance measurements in magnetic fields of up to 55 T, and Hall resistivity and transverse magnetoresistance measurements in fields of up to 15 T for single crystals of CeRhSb with a pseudogap in the density of states. The magnetization at 1.3 K shows rather weak anisotropy along the orthorhombic principal axes, M
a≅ M
b > M
c, and the initial straight lines deviate upward near magnetic field values of 20, 30 and 25 T, respectively. The longitudinal magnetoresistance at 1.3 K is largely negative for both B//a and B//b and saturates near 30 T, while that for B//c is positive. The transverse magnetoresistance is positive and increases in proportion to B
1.5 for B//c, while those for B//a and B//b saturate at around 10 T. The Hall coefficient for B//a changes sign from positive to negative below 4 K, while that for B//c progressively increases with decreasing temperature. The Hall resistivity for B//a and B//b possesses, respectively, negative and positive extrema at 10 T, whereas that for B//c increases linearly with B. These results indicate that the pseudogap in CeRhSb is suppressed for fields B//a and B//b above 10 T and almost disappears near 30 T, while it is hardly affected for B//c. This anisotropic field effect is markedly different from that of the isostructural Kondo semimetal CeNiSn, the pseudogap of which collapses in fields above 15 T only for B//a.
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Fumio Komori, Ken Hattori, Takao Iwaki
Subject area: Superconductivity.
1998 Volume 67 Issue 8 Pages
2614-2617
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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Tunneling spectra are measured at various positions on iron-depositedsurfaces of superconducting 2H-NbSe
2 crystals using scanning tunnelingmicroscopy at 4.2 K. Iron islands are formed on the surface at the initial deposition stage at room temperature. For isolated iron islands, the spectra around the islands are slightly modified from the original for the superconductor and depend on the distance from the islands. The spectra change significantly and have spatial dependence on the surface where iron islands are randomly and densely distributed. The spatial changes are discussed with inhomogeneous magnetic scatterings of substrate superconducting electrons by the iron islands.
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Mitake Miyazaki, Keita Kishigi, Yasumasa Hasegawa
Subject area: Superconductivity.
1998 Volume 67 Issue 8 Pages
2618-2621
Published: August 01, 1998
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The upper critical field H
c2(T) of tight-bindingelectrons in a three-dimensional lattice is investigated. The electrons form Cooper pairs between eigenstates with the sameenergy in a strong magnetic field. The transition lines in the quasi-one-dimensional case are shownto deviate from the previously obtained results when the hopping matrixelements along the magnetic field are neglected. In the absence of Pauli pair breaking the transition temperature T
c(H) of the quasi-two-dimensional electrons is found to increase in an oscillatory manner as the magnetic field becomes large and to reach T
c(0) in the strong field, as in the quasi-one-dimensional case.
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Tohru Nakano, Naoki Momono, Migaku Oda, Masayuki Ido
Subject area: Superconductivity.
1998 Volume 67 Issue 8 Pages
2622-2625
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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We report that in La
2-xSr
xCuO
4 (La214) and Bi
2Sr
2CaCu
2O
8+δ (Bi2212), the resistivity ρ and magnetic susceptibility χ decrease more sharply below T
*, corresponding to the onset temperature of a spin gap (pseudogap) at least for Bi2212. In each system, T
* scales with the superconducting gap magnitude 2Δ
0 (T
*-- 2Δ
0/4.3k
B), which increases as the doping level is lowered. We also report that 2Δ
0 is almost proportional to T
max (>T
*), where T
max is the temperature exhibiting a broad peak of χ and k
BT
max has been considered to give the measure of effective exchange energy J
eff; the α factors in 2{Δ}
0-- α k
BT
max-- α J
eff are nearly one and two for La214 and Bi2212, respectively.
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Akito Kobayashi, Atsushi Tsuruta, Tamifusa Matsuura, Yoshihiro Kuroda
Subject area: Superconductivity.
1998 Volume 67 Issue 8 Pages
2626-2629
Published: August 01, 1998
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Effects of quasi-2D fluctuations on superconducting transition mediated by spin-fluctuations via superexchange interactions in the d-p model are investigated based on the formalism first employed by Nozi\grave{e}res and Schmitt-Rink together with the slave-boson technique and expansion from the limit of the large spin-orbital degeneracy N (1/N-expansion). By calculating superconducting transition temperature T
c, NMR relaxation rate 1/T
1 and Knight shift K, these effects are shown to account for qualitative features of the phase transition observed in high-T
c superconducting materials.
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Toru Sakai, Yoshinori Takahashi
Subject area: Magnetic properties and materials.
1998 Volume 67 Issue 8 Pages
2630-2632
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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Dynamical properties of 2D antiferromagnets with hole dopingare investigated to elucidate the effects of short-range local magnetic orderon the temperature dependence of the dynamical magnetic susceptibility.We show the pseudogap-like behavior of the temperature dependence ofthe NMR relaxation rate. We also discuss the implications of the results inrelation to the observed spin-gap-like behavior of low-doped copperoxide high-T
c superconductors.
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Ko Mibu, Satsuki Tanaka, Teruya Shinjo
Subject area: Magnetic properties and materials.
1998 Volume 67 Issue 8 Pages
2633-2636
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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Epitaxial Cr/Sn multilayers composed of Cr(001) layers and very thin Sn layers were grown on MgO(001) substrates. The magnetic properties of the prepared multilayers were studied by
119Sn Mössbauer spectroscopy. Magnetic hyperfine fields of 11-- 13, T, which are larger than the value reported for dissolved Sn sites in a Cr matrix, were found to be induced at the Sn nuclear sites of [Cr(t
Cr)/Sn(2, Å)] multilayers (t
Cr=6, 10, 20, and 30, Å) at room temperature. The result indicates that the magnetic ordering temperature of the Cr layers is much higher than the Néel temperature of bulk Cr (T
N=311, K). Possible magnetic structures in the Cr layers are inferred from the size and direction of the magnetic hyperfine field transferred at the Sn nuclear sites.
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Tatsuya Shishidou, Takeo Jo
Subject area: Magnetic properties and materials.
1998 Volume 67 Issue 8 Pages
2637-2640
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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Possible magnetic structures of CoO, which is known to be the second kind of antiferromagnet, are discussed for the cubic phase on the basis of the extended Hubbard model including the 3d spin-orbit coupling and the intra-atomic full 3d-3d multipole interaction in the framework of the Hartree-Fock (HF) approximation. In addition to a collinear single-Q structure, a noncollinear quadruple-Q one, both of which are compatible with the neutron diffraction experiment, are obtained as stable HF solutions. The magnitude of the Co orbital magnetic moment is shown to be as large as -- 1 μ
B.
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Satoshi Tsutsui, Saburo Nasu, Masami Nakada, Nobuyuki M. Masaki, Masak ...
Subject area: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1998 Volume 67 Issue 8 Pages
2641-2644
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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The
238U Mössbauer effect of UO
2 has been investigated in the temperature range from 5.4, K to 280, K. Nuclear Zeeman splitting of the
238U nucleus in antiferromagnetic UO
2 at 5.4, K is 59.1± 3.9, mm, s
-1 and corresponds to the value of 252.3± 0.5, T obtained by the
235U pulsed NMR technique. The nuclear magnetic moment of the first excited state (I=2
+) of
238U has been determined to be 0.254± 0.015μ
N. The conversion factor of 4.27± 0.28, T/mm, s
-1 enables us to determine the hyperfine magnetic field at the
238U nucleus using
238U Mössbauer spectroscopy. The temperature dependence of the recoil-free fraction of the
238U Mössbauer effect in UO
2 has been discussed.
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Alexandru Popa
Subject area: Mathematical methods in physics.
1998 Volume 67 Issue 8 Pages
2645-2652
Published: August 01, 1998
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Recently we have demonstrated in a mathematical paper the following property: The energy which results from the Schrödinger equation can be rigorously calculated by line integrals of analytical functions, if the Hamilton-Jacobi equation, written for the same system, is satisfied in the space of coordinates by a periodical trajectory. We present now an accurate analysis model of the conservative discrete systems, that is based on this property. The theory is checked for a lot of atomic systems. The experimental data, which are ionization energies, are taken from well known books.
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Taichiro Takagi
Subject area: Mathematical methods in physics.
1998 Volume 67 Issue 8 Pages
2653-2657
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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We study analytic expressions for the averaged fraction of each vertex type of the six-vertex model extensively. Upon the critical line the expressions of the quantity in theanti-ferroelectric phase and in the gapless phase get simplified.This enables us to see more easily the equivalence of the two quantitiesof which one is derived by differentiating the free energy, and the other is bycalculating a trace of the vertex operators in the theory ofa quantum affine algebra.We also prove an extra liner relation satisfied by the fractionson the critical line.
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Hideaki Ujino, Akinori Nishino, Miki Wadati
Subject area: Mathematical methods in physics.
1998 Volume 67 Issue 8 Pages
2658-2665
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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We present the creation, annihilation and number operators for theA
N-1- and B
N-Calogero models with distinguishable particles.In a parallel way to the construction of the Fock space of the quantumharmonic oscillators, we construct the Fock spaces as the simultaneouseigenfunctions of the number operators for the Calogero models.Relationships between the Fock spaces and the knownnonsymmetric orthogonal bases, which are spanned by the variants ofthe Jack polynomials, are presented.
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Tatsuo Shibata, Shin–ichi Sasa
Subject area: Statistical physics and thermodynamics.
1998 Volume 67 Issue 8 Pages
2666-2670
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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An equilibrium reversible cycle with a certain engine to transduce theenergy of any chemical reaction into mechanical energy is proposed.The efficiency for chemical energy transduction is also defined so asto be compared with Carnot efficiency. Relevance to the study ofprotein motors is discussed.
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Tohru Ikegami, Seiji Miyashita, Heiko Rieger
Subject area: Statistical physics and thermodynamics.
1998 Volume 67 Issue 8 Pages
2671-2677
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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The site-diluted transverse field Ising model in two dimensions isstudied with Quantum-Monte-Carlo simulations. Its phase diagram is determined in the transverse field (Γ) and temperature (T) plane for various (fixed) concentrations (p). The nature of the quantum Griffiths phase at zero temperature is investigated by calculating the distribution of the local zero-frequency susceptibility. It is pointed out that the nature of the Griffiths phase is different for small and large Γ.
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Mitsusada M. Sano
Subject area: Statistical physics and thermodynamics.
1998 Volume 67 Issue 8 Pages
2678-2683
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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We apply the semiclassical theory to the two-point level correlator in the crossover regime between time-reversal and non-time-reversal symmetry for a system which exhibits chaos in the classical limit. The diffuson and Cooperon contributions are explicitly derived semiclassically. The expression of the off-diagonal part is different from the previous results by several authors.
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R. Singh, B. S. Bains
Subject area: Nuclear structure.
1998 Volume 67 Issue 8 Pages
2684-2686
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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Magnetic dipole sum rules for single nucleon transfer reactions have been applied to extract the ground state magnetic moments of some odd-A nuclie. The spectroscopic factors from proton stripping and neutron pick-up reactions have been used as input parameters in the sum rule equations. A reasonablely good agreement has been achieved between the calculated and the known magnetic moments.
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Moon Taeg Jeong
Subject area: Nuclear reactions and scattering: specific reactions.
1998 Volume 67 Issue 8 Pages
2687-2694
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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The electromagnetic form factors and pion photoproduction on the trinucleon have been calculated using mesons (π, , ρ, , ω ) and baryons (N, Δ) properties modified by the presence of the nuclear medium. It is shown that use of their modified masses and coupling constants brings the positions of the first minimum for the trinucleon electromagnetic form factors to a little lower values of momentum transfer Q
2 and improves considerably the theoretical results in the region of high momentum transfers. The pion photoproduction on the trinucleon are consistently evaluated with mesons and baryons properties modified in the nuclear medium.
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Hiroshi Yamagami, Yasutami Takada
Subject area: Electronic structure of atoms and molecules: theory.
1998 Volume 67 Issue 8 Pages
2695-2714
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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A formulation is proposed to treat the ground-state properties of anassembly of electrons, interacting mutually through the Coulombpotential and confined by an external potential V whose maximum isfinite so that both bound and extended continuum states appear aseigen states for the one-body Hamiltonian composed of the electronkinetic energy and V.These extended states are found to play a crucial role inincorporating the effect of electron correlation into the localizedground-state many-electron wave function.As an illustration of our formalism, the ground-state energy of a Heatom is calculated in its simplest version and compared rathersuccessfully with experiment as well as the results in other seriousnumerical methods.We also calculate the density and pair distribution functions in thesame version.Special attention is paid to the latter function in this system inorder to elucidate a qualitative difference from that in thehomogeneous electron gas.This function shows clearly that the two electrons with oppositespins in He correlate strongly over quite a long range in contrast tothe common expectation that the ground-state wave function for the Heatom can be described accurately in the Hartree-Fock approximation.
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Zhao–Yang Chen, Yan Xu, Zhi–Cheng Wang
Subject area: Atomic spectra and interactions of atoms with photons.
1998 Volume 67 Issue 8 Pages
2715-2720
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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A three-level ladder atom driven by two coherent laser fields with rather different frequencies in various kinds of reservoirs is considered. Making use of the master equation and Bloch equation, we calculate numerically and show graphically the steady-state populations versus two-photon detuning. We also discuss and compare the two-photon and one-photon processes occurring for various cases. For a squeezed vacuum, only when the carrier frequency of the squeezed vacuum equals the average of frequencies of the two driving fields and the phase matching condition is fulfilled, will there be a strong two-photon resonant absorption from the squeezed vacuum, a characteristic different from absorption of photons from a classical field; Otherwise, the two-photon ab-sorption rate from the squeezed vacuum will be greatly diminished.
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Hiromi Ezaki, Masato Koashi, Nobuyuki Imoto, Eiichi Hanamura
Subject area: Optics.
1998 Volume 67 Issue 8 Pages
2721-2728
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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We demonstrate that m-photon resonant absorption (m=2, 3, … ) in a microcavity produce strong photon number squeezing. The dependence of the Fano factor and the mean photon number on the pumping rate, linear damping rate and m-photon decay rate is investigated analytically and numerically. We show the existence of a lower limit equaling 50\for the radiation field within the cavity in both transient and steady-state cases. This photon-number squeezing is robust against pumping and one-photon dissipation processes.
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Kazuto Ueno
Subject area: Fluid dynamics.
1998 Volume 67 Issue 8 Pages
2729-2734
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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One of the common features of the problems of quantum field theory, critical phenomena and turbulence is that they are characterized by havingvery many degrees of freedom in a region of the size of a correlationlength. The parameter controlling fluctuations over many length scaleswithin the correlation length is mass ratio, reduced temperature andReynolds number, respectively. By comparing the scaling form of criticalphenomena and that of turbulence, it is found that the scaling relation γ=(2-η)ν known in critical phenomena is also satisfied in Kolmogorov's 1941 theory of turbulence, but the values of the scaling exponents associated with K41 theory of turbulence are very different from those of Landau's mean field theory of critical phenomena.
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Masayoshi Taguchi, Shigematsu Shioya
Subject area: The physics of plasmas and electric discharges.
1998 Volume 67 Issue 8 Pages
2735-2741
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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The neoclassical transport coefficients for the radial particle and energy fluxes, and the parallel current of the fusion-produced alpha particles are shown to be expressed analytically by using a variational method and a Padé approximation.The analytic expressions for these transport coefficients can be used for a wide range of parameters in an axisymmetric magnetic field. The explicit calculation in a tokamak with circular cross section shows that the analytic expressions give a quite good approximation to the numerically calculated exact ones for v
c / v
α > 0.2 -- 0.3, where v
c and v
α are the critical velocity and the birth velocity, respectively.
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Wakako Shiratori, Jun–ichi Sakai
Subject area: The physics of plasmas and electric discharges.
1998 Volume 67 Issue 8 Pages
2742-2746
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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We have investigated the dynamics of the electron-positron plasmacloud moving perpendicular to an ambient magnetic field in the background plasma by using a three-dimensional, electromagnetic, and relativistic particle simulation code. The simulation results showthat large amplitude Alfvén waves are excited, while the electromagnetic waves are weakly excited because of the relativistic effect of the cloud particles.Langmuir waves are also excited along the magnetic field, and cloudparticles as well as background pair particlesare accelerated by Langmuir waves along the magnetic field. The maximum velocities of cloud and background particles exceed the initial cloud velocity.
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Hidekazu Ebata, Jun Tokuda, Kenji Maruyama, Masakatsu Misawa
Subject area: Structure of liquids and solids; crystallography.
1998 Volume 67 Issue 8 Pages
2747-2752
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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The time-of-flight neutron scattering measurements were carried out for liquid CS
2. In order to study coordination structure, Revere Monte Carlo (RMC) fit have been performed. The obtained molecular configurationsare independent from the number of molecules or the initialconfiguration. It is found that the nearest-neighbor CS
2 molecule forms up parallel configuration and the distance between the centers of molecules is about 3.8 Å.On the other hand, the CS
2 molecules at distance of5.0 Å form T configuration.
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Yasuhiro Senda, Fuyuki Shimojo, Kozo Hoshino
Subject area: Structure of liquids and solids; crystallography.
1998 Volume 67 Issue 8 Pages
2753-2757
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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We have carried out an ab initio molecular-dynamics simulation for liquid Li
0.61Na
0.39 alloys at four temperatures above and below the phase-separating temperature and have investigated the structure and electronic states to understand the microscopic mechanism of the phase separation. The calculated concentration-concentration structure factors S
CC(k) show the same characteristic features as those observed for the zero-alloy Li
0.61Na
0.39 by the neutron scattering experiment.It is seen from the calculated electron density distribution that, near the phase-separating temperature, the Li ions tend to assemble together in the region where the electron density is high. This feature can be understood based on the difference in the pseudopotential of Li and Na ions. The relation between the ionic configuration and the electron density distribution obtained for the bulk liquid Li--Na alloys is similar to that obtained for the Li--Na clusters.
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Masayuki Kawakami, Takeshi Uchimura
Subject area: Structure of liquids and solids; crystallography.
1998 Volume 67 Issue 8 Pages
2758-2760
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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X-ray powder diffraction and thermal expansion measurements were made for the Fe
2V
1-xT
xSi (T=Mn, , Cr) compounds below room temperature. With decreasing temperature T, the intermetallic Fe
2VSi compound (x=0) shows the first order transition from the cubic L2
1-type to the tetragonal structure at -- 120, K, at which the lattice expands by nearly 1× 10
-3 in volume. The lattice constants a and c are given as a function of T. The transition temperature decreases monotonically with increasing x, and vanishes at x-- 0.08.
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Akito Igarashi, Toyonori Munakata, Ayuko Inoue
Subject area: Lattice dynamics and crystal statistics.
1998 Volume 67 Issue 8 Pages
2761-2767
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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Dynamical properties of kinks in the discrete Frenkel-Kontorova modelare investigated with the aid of molecular dynamics methodwith special attention to kink propagation, kink-pair nucleationand dislocation propagation under an external force.The activation energies for these three processes obtainedfrom our simulations are compared with thetheoretical results calculated from our method of constraint(s)and the transition state theory. Simulation results arein good agreement with the theoretical ones.
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Kenji Harada, Naoki Kawashima
Subject area: Equations of state, phase equilibria, and phase transitions.
1998 Volume 67 Issue 8 Pages
2768-2776
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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The two-dimensional S=1/2 XY model is investigated with an extensive quantum Monte Carlo simulation. The helicity modulus is precisely estimated through a continuous-time loop algorithm for systems up to 128 × 128 near and below the critical temperature. The critical temperature is estimated as T
KT = 0.3427(2)J. The obtained estimates for the helicity modulus are well fitted by a scaling form derived from the Kosterlitz renormalization group equation. The validity of the Kosterlitz-Thouless theory for this model is confirmed.
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Jirka Hlinka, Hiroshi Orihara, Yoshihiro Ishibashi
Subject area: Equations of state, phase equilibria, and phase transitions.
1998 Volume 67 Issue 8 Pages
2777-2779
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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Dynamics of phase solitons in the polar commensurate phase isanalysed in the framework of the phenomenological model usually used todescribe the commensurate-incommensurate phase transition of the first kind, assuming the continuous order parameter and the constant amplitude approximation.Comparison with domain walls in the usual ferroelectric phase is provided. While the mobility of a usual ferroelectric domain wall diverges at the continuous phase transition to the disordered state, soliton mobilityremains finite at the commensurate-incommensurate phase transition.
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Tomoyuki Hikita, Kazuo Itoh, Kazuo Gesi
Subject area: Equations of state, phase equilibria, and phase transitions.
1998 Volume 67 Issue 8 Pages
2780-2783
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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Mössbauer spectrum of
57Fe of [N(CH
3)
4]
2FeCl
4 was measured as a function of temperature in the temperature range 20-- 290, K. Single doublet was observed in the orthorhombic phase (phase I). The spectrum is almost the same in the incommensurate phase (phase II) and in the phase II
′ where the structure is modulated in the z-direction with the wavenumber 3/7. These modulation seems to raise no large EFG (electric field gradient) modulation to cause noticeable change in the spectrum. A new doublet appears in the phase III where the structure is commensurate with the cell tripling along the c axis. This doublet persists even to the phase IV where the structure is monoclinic with Z=4. If we consider the crystal symmetry, the extra doublet is prohibited in this phase. The extra EFG is interpreted as the peculiarity to the powder sample.
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Masakazu Murakami, Hidetoshi Fukuyama
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 8 Pages
2784-2791
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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The results of the mean field studies on the effects of the backward scattering with large momentum transfer in a two-dimensional electron system are extended to the case with various types of the Fermi surfaceand coupling constants.It is found that the coexistent state of d-wave superconductivity, antiferromagnetism and π-triplet pair can be stabilizedquite generally near half filling.
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Takuya Okabe
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 8 Pages
2792-2801
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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On the basis of the Fermi liquid theory, we investigate the many-body effect on the Drude weight. In a lattice system the Drude weight D is modified by electron-electron interaction, while it is not renormalized in a Galilean invariant system. This is explained by showing that the effective mass m' for D∝ n/m' is defined through the current, not velocity, of quasiparticle. It is shown that the inequality D>0 is required for the stability against the uniform shift of the Fermi surface. The result of perturbation theory applied for the Hubbard model indicates that D as a function of the density n is qualitatively modified around half filling n-- 1 by Umklapp processes.
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Shugo Suzuki, Kenji Nakao, Kenichi Imaeda, Chikako Nakano, Hiroo Inoku ...
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 8 Pages
2802-2806
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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We investigated theoretically the electronic structure of a newC
60 based superconductor, Na
xH
yC
60 where x -- 3.6and y -- 1, to provide criteria that enable one to identify whichof two possible phases, Na
3HC
60 and Na
4HC
60, isimportant to the superconductivity. Studying these two phases byusing the first-principles calculations, we found remarkabledifferences in the electronic structures between them, especially inthe partial densities of states and the nuclear-quadrupoleinteraction of
23Na. We propose that these quantities can workas the criteria for the identification.
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Hiroaki Ohtani, Toshio Yamaguchi, Fumiko Yonezawa
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 8 Pages
2807-2814
Published: August 01, 1998
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The purpose of this work is to give a theoretical explanationof the nonmetal-to-metal (NM-to-M) transition observed in liquid Se when the system is expanded by increasing temperature in the liquid-vapor supercritical region. The NM-to-M transition accompanying the expansion of the system isunexpected since it is in contradiction to the established understandingof NM-to-M transitions. We introduce structural models for expanded Se and calculatethe electronic states and the wave functions of these models by the simulated annealing method.From the results of our calculations, we show that, when some of Se--Sebonds are weakened in the process of expanding the system or equivalently in the processof decreasing the density, the splittingbetween the bonding and anti-bonding level is reduced and consequentlythe anti-bonding band is relatively lowered, which leads to the disappearance of theband gap between the anti-bonding and lone-pair band, or in other words to the occurrence of the NM-to-M transition.
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Akimasa Sakuma
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 8 Pages
2815-2817
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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Magnetic structure of γ -Mn which is experimentally believed to be a collinear antiferromagnet with lattice distortion of c/a < 1 is investigated by taking the non-collinear spin structures into account in the LMTO-ASA. Comparison of the total energies for various magnetic structures indicates that at c/a=1 the non-collinear antiferromagnetic structure is more stable than the collinear structure, although the energy difference is quite subtle (less than 0.1, mRy/atom). It is shown that the lattice distortion to c/a < 1 is strongly responsible for the collinear antiferromagnetic structure and it simultaneously makes the system stable.
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Kiiti Siratori, Yoshinobu Ishii, Yukio Morii, Satoru Funahashi, Sakae ...
Subject area: Electron states in condensed matter.
1998 Volume 67 Issue 8 Pages
2818-2827
Published: August 01, 1998
Released on J-STAGE: October 01, 1999
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Diffuse scattering of neutrons from a single crystal of Fe
3O
4 was measured at 125 K, in the high temperature phase, in a wide range of the (001) and (011) plane. The scattering have been interpreted as due to the lattice distortion accompanied by the charge fluctuation in the B site Fe ions of the spinel structure. Intensities at 19 X points were analysed on an assumption that the displacement of atoms are composed of phonon modes belonging to one symmetry representation of the space group of the whole spinel lattice, instead of the symmetry of some lattice points. It was concluded that the symmetry of the atomic displacement is X
3, containing 12 bases. Quantitative estimate was given for the contribution of each mode and the dynamic structure of a large polaron was determined. The structure is completely different from those proposed so far, on the Fe
2+ - Fe
3+ ordering model.
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