1992年, 第18卷, 第4期　
刊出日期：1992-12-15

  

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  Influence of Electron-Phonon Interactions on the Physical Properties of an Interface Polaron

  Ze HU, You-Tang WANG, Shi-Wei GU, T.C. AU-YEUNG, Y.Y. YEUNG

  理论物理通讯. 1992, 18(4): 385-394.

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  Taking into account the interactions of both bulk longitudinal optical (LO) pltonons and surface optical (SO) pltonons and using Haga's perturbatioit method, we derive an effective Hamiltonian for the interface magnetopolaron in polar crystals at zero temperature. We illustrate in details how to solve this effective Hamiltonian analytically and we obtain explicit formulae not on1y for the electron cyclotron mass associated with the Landau levels but also for the self-trapping energy of the magnetopolaron with respect to its first three quantum states in the direction normal to the interface of the system. Numerical results are calculated for some Ⅱ-Ⅵ and Ⅲ-Ⅴ semiconductor compounds,indicting that the bulk LO phonons and SO phonons do have different trends of effects on the electron in different quantum states.
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  Impurity Effects on Overlayer Structures

  Wen-Chang LU, Tao ZHANG, Kai-Ming ZHANG

  理论物理通讯. 1992, 18(4): 395-398.

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  The Green function method and the tight-binding approximation are employed to study the indirect interaction between two adatoms. Overlayer structures of hydrogen, oxygen and haloid adsorbed on contaminated nickel substrates are explained. The impurity effects are described by the Koster-Slater model. It is found that the introduction of impurity atoms can even change the overlayer structures.
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  The Spectrum of Four-Point Hubbard Model with Holes

  Zhi SONG, Zhen-Qing YANG, Guo-Zhu HE

  理论物理通讯. 1992, 18(4): 399-402.

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  The spectra of four-point Hubbard model with one and two holes are given. The analytic results are compared with those of t-J and t-t′-J models. For one-hole case there exists a phase transition in the groundstate. The transition point is at t/U=0.054.
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  Relations of Systematic Adiabatic Approximation and Stochastic Adiabatic Approximation

  Jing-Hui LI, Li CAO, Da-Jin WU

  理论物理通讯. 1992, 18(4): 403-410.

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  A set of nonlinear stochastic differential equations is treated by using the systematic adiabatic approximation and stochastic adiabatic approximation under the circums tance of Stratonovicl~. Then the results obtained are compared. The comparison shows that the results are identical under the conditions of assumptions of the smallness parameters.
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  The Boyle Curve of Two-Dimensional Fluid System in the Unharmonic Vibration

  Rui-lun ZHENG, Xiu-Ying WU, Sheng-Hong ZHAO

  理论物理通讯. 1992, 18(4): 411-418.

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  By considering the existence of the vacancy and the unharmonic vibration of the atoms, the thermodynaniic functions of the two-dimensional system are calculated in terms of the Collins model and the Ar is taken as an example. The critical point, Boyle temperature and Boyle curve when the translational and vibrational nlotions are taken accorint of are discussed. The results are close to the esperin~ental data and tlie values calculated by empirical formulae.
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  Multivortex Solutions in (2+1)-Dimensional Abelian Higgs Model with a Chern-Simons Term

  Zhong-Shui MA, Lian HU, C.C. LAM

  理论物理通讯. 1992, 18(4): 419-426.

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  The multivortex solutions of (2+l)-dimensional Abelian Higgs model with a Chern-Simons term are stlrrlied. The Bogomol'nyi-type equations and corresponding Weinberg's index theorem have been derived for a sixth-order Higgs potential. The magnetic field is different from that of the Abelian Chern-Simons Higgs model which has no Maxwell term, and has a maximum at the center of the vortex.
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  Upper Bounds on Top Quark Mass, Z Boson Decay Widths and Mass Ratio M_W/M_Z

  Zhen-Jun XIAO, Gong-Ru Lu, Yi-Bing DING

  理论物理通讯. 1992, 18(4): 427-434.

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  In this paper we made a comprehensive analysis of some latest esperimental data-the Z boson decay widths, the mass ratio M_W/M_Z and effective vector coupling constant g_v, within the framework of standard model. We considered the 0(α_s²), order QCD corrections in tlte calculation of T_h and T_z. The analysis shows that the mass ratio (M_W/M_Z)² is rather sensitive to the change of the strong coupling constant α_s(M_Z), and the smaller value α_s(M_Z)≤0.128 is preferred. The upper bounds on top quark Inass M_t are obtained from different analyses. The final averaged result is M_t= 102 37 GeV, or M_t< 186 GeV at 95% C.L. for Higgs boson mass M_H in the range of 50～1000 GeV.
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  Sewing Construction in KN Operator Formalism of Conformal Field Theory

  Qi-Hua CHENG

  理论物理通讯. 1992, 18(4): 435-442.

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  It is shown that the KN operator formalism for a nonchiral bosonic system can be extended to higher genus Riemann surfaces with K+2 punctures by using the construction of conformal field theories. This completes the full formulation of the KN opera tor formalism and preparation of describing bosonic string scattering amplitudes. We also elaborate on the sewing prescription further.
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  Localization of the Poincare Group in the Spinor Space

  LIU Yu-Fen

  理论物理通讯. 1992, 18(4): 443-450.

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  A more general representation of the Poincare group where translation generators are generalized by P_μ= i∂_μ+kγ_μ[(l+γ₅)/2] is discussed. The corresponding spinor gauge field is studied in detail. It is shown that the Lagrangian of fermion keeps its form invariant under the above translation. An additional hidden symmetry of the Dirac field leads to a prediction of existence of an intrinsic energy-momentum for the fernlion.
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  The Phase Transition in the Three-State Potts Model: An Analytical Analysis

  Y.X. SONG, J.M. YANG, G.R. LU, J.Y. CUI

  理论物理通讯. 1992, 18(4): 451-456.

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  Weinvestigate thephase transition of the three-state Potts model in an analytical approachthe generalized cumtilant expansion with the effective mean field Itypothesis. We find a first order phase transition in the three-dimensional three-state Pot ts model with ferromagnetic nearest neighbor (nn) coupling. For the model with antiferromagnetic next-to-nearest neighbor (nnn) coupling, pe find a first order transition when tlle relative strength of the nnncoupling γ is fixed to -0.2. The critical values given by this method are also in agreement with the recent high statistics Monte Carlo results.
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  Quantum Stimulated Raman Scattering

  Shui-Yin LO, Tu-Nan RUAN

  理论物理通讯. 1992, 18(4): 457-464.

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  The quantum field theory of stimulated Raman scattering is formulated. It is shown to give the correct classical limit. Ilowever, the quantum growth rate is bigger. An additional physical process of creation of two plasmons from two photons is intrinsically predicted by the theory.
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  Study of a Frustrated Heisenberg Antiferromagnetic Model in Two Dimensions

  Shi-Min CUI

  理论物理通讯. 1992, 18(4): 465-468.

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  A two-dimensional (2D) frustrated IIeisenberg antiferromagnetic (AF) model with next nearest-neighbor exchange couplings on the squarelattice is studied by using Green's function technique. It is shown that there always exists a finite zero-temperature staggered magnetization in contrast to the conventional spin-wave calculations, indicating the existence of the Neel-type long-range order in the ground state even for strong frustration.
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  Superconductivity in La_1.85Sr_0.15Cu_1-xZn_xO₄

  Fu-Sui LIU

  理论物理通讯. 1992, 18(4): 469-470.

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  Based on the multiple exchange-mediated interaction mechanism of high-T_c superconductivity and the Abrikosov-Gorfiov theory of magnetic impurity superconductors, this letter quantitatively explains the Zn-substitution experiment of La_1.85Sr_0.15Cu_1-xZn_xO₄
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  Evaluation of the Boltzmann Density Matrix with Coupling Term by Monte Carlo Random Walk Method

  Jing-Dong BAO, Yi-Zhong ZHUO, Xi-Zhen WU

  理论物理通讯. 1992, 18(4): 471-474.

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  A Monte Carlo random walk algorithm for evaluating the path integral expression for coordinate matrix elements of the Boltzmann operator with the coupling term is suggested and discussed.
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  Centrifugal Electrical Force

  A.K.T. Assis

  理论物理通讯. 1992, 18(4): 475-478.

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  We calculate the force on a point charge moving within a charged spherical shell spinning with ω(t) according to Weber's law. We compare this result with the one given by Lorentz's law and show that Weber's law predicts an extra centrifugal electrical force and an extra inertial electrical force. We give orders of magnitude for these forces and propose some experiments to test the existence of these terms.
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  Proton-Calcium Scattering at T_p=200 Mev in the α-Particle Model

  Wen-Ying RUAN, Yi-Wu DUAN

  理论物理通讯. 1992, 18(4): 479-482.

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  Elastic proton-⁴⁰Ca scattering at T_p = 200 MeV is calculated within the Glauber theory on the basis of the α-particle model. The results are compared with the experimental data and those calculated in the relativistic model.
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  Constraints on Form Factor Ratios and Bounds on υ(υ)N Scattering in the Standard Model

  Mujahid Kamran

  理论物理通讯. 1992, 18(4): 483-486.

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  Using PQCD and the standard electro-weak theory we prove that F₁ⁿ/F₁^p must be nonzero and finite at large momentum transfers. This has implications for QCD sum rule based nucleon wave functions. Bounds on combinations of υ(υ) N differential cross sections are derived. Relations involving F₁ⁿ/F₁^p and [F_A/F₁^p]² are obtained and it is established that at large q², F_A/F₁^p must be finite where F_A is the axid form factor.
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  Gravitational Scalar-Driving Inflation

  Mian WANG

  理论物理通讯. 1992, 18(4): 487-490.

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  We discuss the cosmological inflation from the point of view that in the very early universe the gravitation governs the cosmological dynamics solely and the inflation is driven by the gravitational scalar field through the cosmologicd function λ(φ). In the meantime, a new theory of gravitation is proposed which gives a satisfactory inflation model for the very early universe and identifies itself with the Einstein theory at present day due to the infinite value of the coupling function ω(φ) when φ tends asymptotically to φ_A = 1.
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  Suppression of Retrieval States in Spin-Glass-Like Model of Neural Networks with Random Neuronal Threshold

  Yu-Qiang MA, Yue-Ming ZHANG, Chang-De GONG

  理论物理通讯. 1992, 18(4): 491-494.

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  We propose a mechanism to consider the effects of the random neuronal threshold on the retrieval properties of neural networks. The retrieval properties of the fully asymmetric Sherrington-Kirkpatrick (SK) and Hopfield models are studied, respectively. We show that the ferromagnetic retrieval states are destroyed by fluctuations induced by random neuronal thresholds.
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  Random Neural Network with Local Gauge symmetry

  Zhi-Bing LI, Xiao-Wei LIU

  理论物理通讯. 1992, 18(4): 495-496.

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  Here we propose that the model of random surfaces coupling with spins in a local gauge symmetric manner may be closely related with the biological neural networks. We argue that the local gauge symmetry is a rather general requirement for the neural network models.