1995年, 第23卷, 第1期　
刊出日期：1995-01-30

  

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  Hot-Electron Transport and Coupled-Mode Optic Phonon in a Polar Semiconductor

  M. W. WU, X. L. LEI

  理论物理通讯. 1995, 23(1): 1-10.

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  The effect of coupled-mode-LO phonons on the electronic transport in a polar semiconductor is studied within a model which takes the internal thermalization time of the LO phonon system and the relaxation time of the whole lattice as parameters. Our analysis shows that although the hot-electron energy-loss to LO phonons is drastically enhanced and the LO-phonon-induced linear mobility is markedly reduced by the formation of coupled modes at low temperatures, in a realistic polar semiconductor when all the scattering mechanisms included, the coupled-mode effect on the transport properties is almost buried.
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  Theoretical Calculation of Drag Component of Tensor M in Quantizing Magnetic Field

  G. QIN, P. N. Butcher, J. P. Oxley, B. L. Gallagher, B. G. Mulimani

  理论物理通讯. 1995, 23(1): 11-18.

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  All the previous homogeneous theories result in M_ΧΧ = 0 which are at variance with the experimental data. It is for this reason, previous theories have consistently used experimental value of M_ΧΧ in calculating thermopower tensor S. The inhomogeneous and non-equilibrium formalism proposed by Dyakin et al. was generalized to including both transverse and longitudinal modes of electron-phonon interaction and considering the broadening of the Landau level. The resulting formula gives theoretical values of M_ΧΧ for GaAs/AlGaAs heterojunctions which are in accord with experimental ,data at oscillation phases but (λ_p/)^l/2 times smaller than experimental data for T = 1.275 K, 2.937 K, 5.005 K and C = 0.20 where λ_p and are the phonon mean free path and effective thickness of the heterojunctions. By means of the semi-empirical formula of MzZ with extra factor (λ_p/)^l/2 in, phonon drag magnetothermopower can be calculated from theoretical values of M_yΧ and M_ΧΧ.
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  Pseudo-Fermion Method of Spin = 1 and Multiple-Exchange-Mediat ed Interaction

  Fu-Sui LIU, Ming SHAW, Wan-Fang CHEN

  理论物理通讯. 1995, 23(1): 19-24.

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  Using the Abrikosov's pseudo-fermion representation of a single spin S and the Larsen's note with pseudefermion energy λ = 0, we describe a procedure which allows calculation of spin-spin interaction as well ts spin-electron (hole) interaction for the case of spin S = 1 by usingstandard methods including the linked cluster theorem of diagrammatic perturbation theory. In particular we derive the multiple-exchange-mediated interaction in the case of S = 1 and predict the possibility of a higher Tc such as 170 K.
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  Numerical Calculations for the Surface on a Semi-Infinite Ising Model with a Random Surface Field

  Gang SUN, Jie YANG

  理论物理通讯. 1995, 23(1): 25-30.

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  We study the critical behavior of the surface on a semi-infinite simple cubic lattice Ising model with a bimodal random surface field by large cell mean-field renormaliza tion group method and Monte Carlo simulations. Our results show that the surface ferromagnetic phase exists in the weak random field range above the bulk critical temperature. The surface. specific heat is not divergence and the susceptibility show a cusp singularity at the surface ferromagnetic-paramagnetic transition for a relatively large and om field.
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  Effect of an External Magnetic Field on the Plasmon Polaritons of Thue-Morse Semiconductor Superlattices

  Nian-Hua LIU, Wei-Guo FENG, Xiang WU

  理论物理通讯. 1995, 23(1): 31-36.

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  The collective magnetoplasmon polariton excitations in a semiconductor superlattice with the thicknesses arranged in Thue-Morse sequence are studied. We take the effect of retardation into account and assume the system is subjected to an external static magnetic field applied parallel to the interfaces. It is found that the spectrum of the polariton has the Cantor-like structure, and the total widths of the bands show scaling properties with increasing the generation. The external magnetic field makes the bands become more narrow and shift to higher frequencies for the optical modes and to lower frequencies for the acoustic modes. For a given excitation frequency, the localization properties,of the modes will be changed if we vary the external field.
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  Analysis and Discussion About How to Determine the Variatiotnal Parameters in the Variational-Cumulant Expansion

  Rui-Jie LIU, Tian-Lun CHEN

  理论物理通讯. 1995, 23(1): 37-44.

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  Four methods of determining the variational parameter in the varia tional-cumulant expansion (VCE) are studied on the 2-dimensional Ising model. A comparison with the exact result shows that the main-variation method is the best one at low temperature, the completevariational method is better than others at high temperature, the accumulation-point method is the best one to approximate the intermediate coupling region, and each of the methods is analyzed from the original formulas or conjectures. Some suggestions are given in order to get optimal results. The VCE is also analyzed Gom a point of view of symmetry breaking for the first time.
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  Correlated Noises of the Stochastic Processes

  Ya JIA

  理论物理通讯. 1995, 23(1): 45-50.

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  The combined effect of several noises has been proposed recently. It has displayed that the presence of the correlation between noises can change the properties of the stochastic processes. In this paper, a general effective Fokker-Planck equation (FPE) with correlated noises is derived. The stationary distributions and the moments of two kinetic models under two correlated noise sources are obtained. The effects of the interference of additive and multiplicative noises are analyzed.
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  A Hierarchical Neural Network Model Suitable for Storing Correlation Patterns

  Wu-Qun HUANG, Cheng-Qun GAO, Tian-Lun CHEN

  理论物理通讯. 1995, 23(1): 51-56.

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  An improved hierarchical cascade model (PIDD model) has been obtained by using pseudoinverse method without degenerate states in the framework of the hierarchical model improved by Deshpande, the PIDD model not only avoids errors on classification of patterns, but also suits to store correlative patterns. The dynamic behavior of the PIDD model has been analyzed, and phase structure and self-consistent equations have also been obtained ,by using the replica method.
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  Linear Quantum Transform Theory in Bargmann-Fock Space and Its Preliminary Application

  Yong-De ZHANG, Zhong TANG

  理论物理通讯. 1995, 23(1): 57-64.

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  A general theory for the linear transform in Bargmann-Fock space of n-mode boson system is presented. The group structure of transform is analyzed and the explicit expressions of transform operations in terms of normal ordering are given. As applications, a series of useful iden tities are given, the decoupling problem for general two-boson interaction and the normal product calculation of boson exponential quadratic operators are studied.
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  Formal Series Symmetries and Truncated Symmetries of a Bilinear Schrödinger Equation

  Jun YU, Ji LIN

  理论物理通讯. 1995, 23(1): 65-68.

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  For a type of nonlinear Schrodinger equations, we get a set of formal series symmetries. For a special integrable bilinear Schrodinger equation in (2 + 1)-dimensional spacetime, some truncated symmetries which constitute an infinite dimensional Lie algebra are obtained.
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  Symmetries and a Hierarchy of the Combined KdV-mKdV Equation

  Jie-Fang ZHANG, Ji LIN

  理论物理通讯. 1995, 23(1): 69-72.

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  We first give for the combined KdV-mKdV equation, an inverse strong symmetry and five symmetries, and then we constitute six sets of symmetries and a generalized hierarchy of combined KdV-mKdV from these symmetries by using strong symmetry and its inverse.
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  The Extended W₃² Toda System with Conformal Weights in 1/3 Sequence

  Huan-Xiong YANG, Bo-Yu HOU

  理论物理通讯. 1995, 23(1): 73-82.

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  In this paper we suggest a new prescription for the Hamiltonian reduction of the SL(3, R)WZNW model by generalizing the famous BFOFW theory. As a result, a conformal system with conformal weights in 1/3 sequenceis induced. We call the system the extended W₃² Toda model because its conformal invariance is described with a nonlinear W₃²-algebra. Relying on the analyses in this paper, it seems that the Hamiltonian reduction procedure itself, for WZNW model, does not demand that the survived Kac-Moody currents should be preserved to have clear conformal dimensions.
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  Structure Phase Transitions of the (D + 1)-Dimensional Double sine-Gordon Field Theory

  Yue-Jing ZHU, Sen-Yue LOU

  理论物理通讯. 1995, 23(1): 83-92.

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  Using the thermal coherent state approach, we investigate the finite temperature quantum double sine-Gordon (DsG) field theory. From the stability conditions of the vacuum states of effective potential, the exact soliton-like solution of the field equation and the resemblance between the DsG model andλφ⁴ model, we show that there exist two types of structure phase transitions among four structures of the (D+1)-dimensional DsG model similar to the symmetry restored phase transition of λφ⁴ model. For the first type of phase transition, the small kink-like solutions will disappear at the critical temperature while the large kinklike solutions will be changed continuously at the critical temperature. For the second type of the phase transitions, the metastable localized soliton-like solution will disappear, while the stable kink-like solution exists for all the temperatures and their exact form is also independent of the temperature being under or over the critical temperature.
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  Quantum Theory of Vibron Soliton

  Sai-Jun YU, Yi XIAO

  理论物理通讯. 1995, 23(1): 93-100.

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  A quantum mechanical treatment of Takeno model for energy transport in protein is presented and the cubic anharmonicity of the hydrogen-bonded interaction is also taken into account. Under the continuum approximation, two coupled nonlinear differential equations are obtained, and then exact and approximate solitary wave solutions are found. The ideal parameters for protein are used to show whether the soliton solutions can exist for real protein molecules.
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  Glauber Approximation in the Laser-Assisted Charged Particle Hydrogen Atom Inelastic Collisions

  Ji CHEN, Zi-Fang ZHOU

  理论物理通讯. 1995, 23(1): 101-104.

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  The Glauber approximation in the laser-assisted inelastic collisions is derived in detail. The scattering S-matrix elements are successfully reduced so that the analytical expressions for S-matrix elements are obtained. An example for numerical calculation is given and the results are compared with the first Born approximation.
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  The Periodicity of Persistent Currents in Mesoscopic Rings

  Jian-Xin ZHU, Z. D. WANG, Chang-De GONG

  理论物理通讯. 1995, 23(1): 105-108.

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  In a tight-binding model, we find that the equation of the Green's function in a onedimensional mesoscopic ring threaded by a Aharonov-Bohm (AB) flux can be exactly solved. From the poles of the Green's function, the eigenvalues are obtained and are periodic in the AB flux with period h/e. However, the periodicity of the persistent currents is determined by the number of electrons in the ring.
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  Equivalence of Bogoliubov Transformations to the Gaussian Wave-Functional Approach in sin-Dordon Model

  Wen-Fa LU, Bo-Wei XU, Yu-Mei ZHANG

  理论物理通讯. 1995, 23(1): 109-112.

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  Through the calculation of the effective potential and the excited state energies for the sinh-Gordon and the sine-Gordon models in (D + 1) dimensions, we show that the variational technique of Bogoliu bov transformations is equivalent to the Gaussian wave-functional approach.
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  Augmented Algorithm for Generation of Constraints

  An-Min WANG, Tu-Nan RUAN

  理论物理通讯. 1995, 23(1): 113-116.

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  It is found that Dirac's original consistency conditions do not suffice to generate all the secondary constraints and determine all the multipliers in front of the second-class constraints for the general singular Lagrangian sys tems. Cawley 's second counter example of Dirac's conjecture just has this feature. This may lead to the fact that the equivalence of Lagrangian and Hamiltonian formalism is not guaranteed and even dynamics of Hamil tonian formalism is not completely determined. In order to overcome the above difficulties, an augmen ted algorithm for generation of constraints-the algorithm of the extended consistency conditions is proposed. In this new algorithm, Cawley's second example is no longer a counter example of Dirac's conjecture.
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  q-Taylor's Formula with Its -Remainder

  Si-Cong JING, Hong-Yi FAN

  理论物理通讯. 1995, 23(1): 117-120.

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  We derive the q-Taylor's formula with its q-remainder through the q-differentiation approach. Comparison between q-Taylor's expansion with the ordinary Taylor's formula is made, which shows that the q-remainder is different from the ordinary one.
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  Chain Solutions of the BKP Equation

  Ying WU, Xim-Xue YANG

  理论物理通讯. 1995, 23(1): 121-124.

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  We obtain a new class of exact analytic solutions of the BKP equation which are called chain solutions because they are analogous to the, soliton solutions of the KP equation. The rational solutions called lumps are shown to include in this class as a Special limiting situation.
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  Wu Algorithm and Solutions of Yang-Baxter Equation for Eight-Vertex Model

  Xiao-Dong SUN, Shi-Kun WANG, Ke WU

  理论物理通讯. 1995, 23(1): 125-128.

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  In this note, we claim that we have obtained all nondegenerate solutions of Yang-Baxter equation with spectral parameter for square-lattice eight-vertex model without "zero-field" conditions by several solution transformations and six basic solutiofis with the help of Wu algorithm.