1991年, 第16卷, 第3期　
刊出日期：1991-10-30

  

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  Ward-Takahashi Identity at Finite Temperature

  Hong-Hua XU, Jun SHEN, Chien-Hua TSAI

  理论物理通讯. 1991, 16(3): 257-264.

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  A new real time formalism, based on the closed-time-path Green's function theory (CTPGF),is employed to obtain Ward-llfrkahashi identities of QED at finite temperature. It is shown that WT identity in coordinate space is of the same covariant form aa that in vacuum field theory. A perturbative check is provided to #how that in momentum spze, Takahashi's iden tities hold only in a weak sense.
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  Determination of Domain of Attraction by Short-Time Overlap Dynamics in Neural Networks

  Bei-Lai HU, Wu-Qun HUANG, Tian-Lun CHEN, Xi-Hui CAO, Cheng-Qun GAO

  理论物理通讯. 1991, 16(3): 265-272.

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  Since the overlap dynamics of spin-glass-like neural network is solely governed by such two parameters, the symmetry of the net's connections and the stabilities of the embedded patterns, we propose that the domain of attraction of a network could be determined by a short-time (at least the first two-step) dynamics, in which both parameters begin to be visible.The first step overlap dynamics Q calculated by probability theory and the second step overlap dynamics for pseudo-inverse-model is obtained by extended Krauth's theory. The calculated domain of attraction for this model is in good agreement with the results obtained by computer simulation.
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  Phenomenological Free-Energy-Function, Fractal Dimension, and Critical Indices for Phase Transition Systems

  Lun-Biao XU, Zhi-Jian WANG

  理论物理通讯. 1991, 16(3): 273-280.

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  Considering the relations between interaction terms in microscopic Hamiltonian and φⁿ terms in macroscopic Landau's free-energy-function (FEF) of a phase transition system, we propose a modified Landau's phenomenological FEF to deal with critical phenomena.According to scaling symmetry, it ie indeed true tiat, the dimension of interaction space is fractal at critical points for a phase transition system. Following these analyses, we obtain all the critical indices reasonably classified in the classes denoted by n, whid satisfy all the scaling laws and coincide with experiments. A cogent example ie given.
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  Electronic States in Quantum Wells with Interface Defects

  Hong SUN, Xing ZHANG, Shi-Wei GU

  理论物理通讯. 1991, 16(3): 281-288.

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  Effects of ilr terface defects on electronic states in quan tum wells (Q Ws) are investigated theoretically by introducing a coordinate transformation that transforms QWs with defective interfaces to those with planar interfaces plus an effective potential associated with interface defects. The interface defects are idealized as a cylindrical hollow protruding into the barrier materials on one of the interfaces. Electronic ground state energies are calculated variationally aa functions of the defect lateral sizes. For GaA8-Ga_1-zAl_zAs Q WS with the well width d less than 150 Å, the changes in electronic energies due to interface defects will produce sizable effects on optical experiments, such as broadenings of excitation spectra of Q We. But our calculation predicts smaller spectrum broadenings than those predicated by the previous theory for the same interface disorder.
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  Some Generalized Scalar Field Models with Abundant Soliton-Like configurations

  Hang-Yu RUAN, Sen-Yue LOU

  理论物理通讯. 1991, 16(3): 289-294.

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  Some generahed scalar field models are presented. It is shown that there exist generally three types of soliton solutions for the extended models. The form of the first type of the soliton solutions is model-independent. An arbitrary constant can be included in the second type of the soliton excitations which is model-dependent. The third type of the soliton solutions is also modeldependent but with no arbitrary constant. The extended φ⁴ model and sine-Gordon model are studied in detail.
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  Super Coadjoint Orbits of the N=2 super-Virasoro Group

  Kong-Qing YANG

  理论物理通讯. 1991, 16(3): 295-302.

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  Based on the conformal variation in conformal field theory, the super coadjoint orbits of, N = 2 super-Virasoro group are classified.
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  Braiding Matrix with a Spectral Parameter for the Quantum Octet Representation

  Yu-Dong YIN, Zhong-Qi MA

  理论物理通讯. 1991, 16(3): 303-310.

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  In this paper the spectrum-dependent solution of the Yang-Baxter equation related to the statistical face model (braiding matrix) for the octet representation of the quantum sl(3) enveloping algebra is computed explicitly. In this example there ie multiplicity greater than one in the decompoeition of the coproduct 8⊗8.
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  The Exact Solution, Berry's Phase and Coherent State for the Driven Generalized Time-Dependent Harmonic Oscillator

  Jing-Bo XU, Tie-Zheng QIAN, Xiao-Chun GAO

  理论物理通讯. 1991, 16(3): 311-318.

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  The Lewis'invariant and exact solution for the driven generalized time-dependent harmonic oscillator is found by making use of the Lewis-Riesenfeld quantum theory. Then, the adiabatic asymptotic limit of the exact solution is discussed and the Berry's phase for thirr system is obtained. We then proceed to use the exact solution to construct the coherent state and calculate the corresponding exact classical phase angle. This phase angle can give the Hannay's angle in the adiabatic limit. The relation between the exact Lewis'phase and the corresponding classical phase angle L'discusrred.
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  Monopole Mass Evaluated by an Arialytic Approximation

  Qiong-Gui LIN, Guang-Jiong NI

  理论物理通讯. 1991, 16(3): 319-324.

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  We propose an approximate method for evaluating the mass of the't Hooft-Polyakov monopole and obtain the result in an analytic form. The antimonopole is also dbcussed.
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  Chern-Simons Gauge Theory and Anyons at Finite Temperature

  Shu-Xue DING, He-Shan SONG, Ing AN

  理论物理通讯. 1991, 16(3): 325-330.

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  The temperature dependence of Chern-Simons coefficient and statistical angle are investigated by using field theory at finite temperature. The results show that the Chern-Simons term will melt away at high temperature and the statistical angle will increase as temperature. increases. Temperature dependence of the filling fact for Landau-Level is also discussed.
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  Extended Application of the Velocity Superselection Rule

  Chao-Hsi CHANG, Xue-Qian Li

  理论物理通讯. 1991, 16(3): 331-336.

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  We have applied the velocity superselection rule proposed by Georgi, bgur and Wise to some transition matrix element calculations in an extended way. We have found that by the approach f_B, is about 0.6-0.8f_K which is consistent with the potential model calculations.
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  Light 0^- Meson Solution of Bethe-Salpeter Equation Involving the Vacuum Condensates in QCD

  Jian-Guo BIAN, Tao HUANG

  理论物理通讯. 1991, 16(3): 337-344.

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  We dkcuss the Bethe-Salpeter equation involving the vacuum condensates in QCD in the backgrouud fields. The bound state equation for the light 0^- meson (π and K) is solved in the ladder approximation of single gluon exchange, where the gluon propagator is calculated in tree level of a gluon condensate and a quark condensate. The kernel is divided into two parts: perturbative and non-pert,urbative. The non-perturbative part is determined by the vacuum condensate. Pseudo-scalar meson spectrum and decay constants are in good agreement with data.
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  Parameters Design of the Birefringent Acousto-Optic Scanning Devices

  Ning-Sheng MA, Jie-Ping XU, Eddie Young

  理论物理通讯. 1991, 16(3): 345-348.

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  We have made analysis and discussion for the AO first order beam steering in TeO₂, precisely investigated the solution of the Dixon equation, and put forward the method of obtaining the greatest bandwidth and decreasing the acoustic wave's walkoff. Various optimum parameters are determined for a two-dimensional AO device.
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  Feynman Diagram Theory of Degenerate Birefringent Bragg Diffraction

  Ning-Sheng MA, Jie-Ping XU, David N. Sitter, William T. Rhodes

  理论物理通讯. 1991, 16(3): 349-354.

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  A Feynman diagram theory for acousto-optic (AO) interaction is established, which supplies a general method to calculate the scattering amplitudes and intensities for both single frequency and multifrequency AO interactions. The method L based on counting the number of allowable Feynman diagrams. Based on this, a complete solution for the scattering amplitudes and intensities an be obtained for any kind of AO interactions, any number of acoustic frequencies, and any final states. A geometrical representation for this Feynman diagram theory of AO interaction is set up too. The theory is ale0 verified by comparing with the experiments.
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  The Critical Behavior of Partially Directed SAW on Sierpinski Carpets

  Kai-Lun YAO, Guo-Ce ZHUANG, JiA-Fu WANG

  理论物理通讯. 1991, 16(3): 355-358.

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  Using the fractal-cell generation method we perform a numerical simulation study for partially directed self-avoiding walks (PDSAW) on Sierpinski carpets. The obtained critical exponents v_H is found to be independent of the fractal dimension of Sierpinski carpet d_f, but v_⊥ is dependent on d_f . This result indicates that PDSAW on different Sierpinski carpets belong to different universality classes. Compared with the fully directed self-avoiding walks (FDSAW) on the same carpets, the obtained results indicate that PDSAW and FDSAW belong to the same universality class.
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  Wei-Norman Algebraic Method Solving the Evolution of the Coherent States of Electron in Two Dimensions

  Chang-Pu SUN, Qing XIAO

  理论物理通讯. 1991, 16(3): 359-362.

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  The Wei-Norman algebraic method is used to solve the evolution of electron in twodimensional cweo in this letter. We show that the coherent stateo of elec tron in two dimensions can be generated by the interaction of electron with a certain type of external electromagnetic field.
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  A Scenario with Tolerable Strong CP

  Zheng HUANG, Dan-Di WU

  理论物理通讯. 1991, 16(3): 363-368.

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  Some missing points and controversies in discussions about strong CP in previous literature are remarked. The equations of vacuum alignment including heavy quarks are shown to be a straightforward generalization of the equations due to Crewther. Di Viccia, Vinesiao, Witten and't Hooft for light quarks and directly related to U_A (1) anomaly equations. A scenario with vanishing dynamical condensate of a heavy quark is proposed as an alternative to a vanishing u quark mass.
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  String Fragmentation Model and Inclusive Production of K^*± (892)

  Fazal-e-Aleem, Mohammad Saleem

  理论物理通讯. 1991, 16(3): 369-372.

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  An account of the inclusive production of K^*±(892) in electron-positron annihilation ia given. The most recent measurements on the cross section are exhibited and compared with the predictions of version 6.3 of the Lund model. A satisfactory agreement is obtained. The results on mean multiplicity per multihadronic event from CELLO, PEP and PETRA collaborations are found to be consistent.
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  String Vertex Operator and Affine Kac-Moody Algebra

  Jun VAN, Shi-Ke HU

  理论物理通讯. 1991, 16(3): 373-376.

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  A general discussion on string vertex operator ie given in this letter. By using the Liedifferential operator, the conformal algebra of A₁⁽¹⁾ theory is shown to admit an infinitedimensional Kac-Moody algebra.
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  Inelastic Pion Scattering from ¹²C at 800 MeV/c

  Jun-Feng SHEN, Yu-Shun ZHANG

  理论物理通讯. 1991, 16(3): 377-380.

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  The differential cross section of the inelastic scattering of pion at 800 MeV/c fir the 3^- excited states of ¹²C is calculated by making use of eikonal approximation and the collective coordinate. The calculation indicates that the 3_- state of ¹²C is octupole vibrational state.The results are in agreement with experimental data.
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  Soliton Chains of Interchange Modes in Plasmas

  Ying WU, Kai-Lun YAO

  理论物理通讯. 1991, 16(3): 381-384.

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  The equation governing nonlinear two-dimensional interchange modes is derived and an exact solution consisting of an infinite chain of solitons is found. It is suggested that soliton chains of interchange modes in plasmas could be observed experimentally.