1998年, 第30卷, 第1期　
刊出日期：1998-07-30

  

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  Calculation of Microwave Multiphoton Transition Probability

  LI Yong, LIU wenyul, RAO Jianguo, LI Baiwen

  理论物理通讯. 1998, 30(1): 1-6.

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  In a phenomenological two-level model, by using Floquet method, we directly calculate the multiphoton transition probability between the Rydberg states of an alkali-metal atom in strong microwave fields. The convergence of the truncated Floquet matrix, and the influences of parameters upon the multiphoton resonant spectra are discussed. The results show that our method can give clearer physical picture and better results about the multiphoton transition than indirect methods. Moreover, our method can easily be generalized to treat multi-level models.
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  Simple Estimates sf the Effective Ranges of Intermolecular Forces of Small Nonpolar Molecules

  GAO Chongyi

  理论物理通讯. 1998, 30(1): 7-12.

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  From the potential model of Lennard-Jones (12-6) and equilibrium separation TO of the intermolecular force, one can give small nonpolar molecule rational and classical estimate of the effective ranges of repulsive intermolecular force γ_λ and the effective ranges of attractive intermolecular force γ_μ with semiempirical formulae: T_λ = 2γ₀, γ_μ = 3γ_λ = 6γ₀. he γ₀ can be sketchily calculated with molar mass and density of the liquid state ρ₁. In this article, we give the values of γ₀,T_λ and γ_λ of seventeen kinds of small nonpolar molecules. As a general rough result, the approximate values are γ₀ = 0.4 nm, T_λ = 0.8 nm, γ_λ = 2.4 nm.
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  Adiabatic Approximation in Interaction Between Two-Level Atom in an External Potential V(χ) and Optical Field

  LIU Xiaji

  理论物理通讯. 1998, 30(1): 13-16.

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  In discussion about the detection of the BoseEinstein condensation, the adiabatic approximation method was taken. According to the perturbation theory, this approximation is studied in detail by a single atom model in this paper.
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  Hardy's Theorem for n Spin-s Particles in Entanglement

  WU Xiaohua, ZHAO Yumin, HSIA Yuanfu

  理论物理通讯. 1998, 30(1): 17-20.

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  The Hardy's theorem [Phys. Rev. Lett. 71 (1993) 1665] is extended to n spin-s particles. As expected, the entangled states for these particles also admit a proof of nonlocality without using inequalities.
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  Spin Waves in a Semi-Infinite Heisenberg Ferromagnet with Magnetocrystalline Anisotropy

  DAI Songtao, LI Zhenya

  理论物理通讯. 1998, 30(1): 21-26.

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  A Green function formalism is employed to investigate the effect of magnetocrystalline anisotropy on surface spin waves in semi-infinite Heisenberg ferromagnets at low temperatures T << T_c. The dispersion relations are investigated in detail. The density of states (DOS) of surface spin waves and layered magnetizations are also derived.
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  Magnetic Excitations and the Curie Temperature of Decamethylchromocenium Tetracyanoethylenide

  BAO Shuqing, SHEN Juelian

  理论物理通讯. 1998, 30(1): 27-32.

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  We describe the molecular ferromagnet decamethylchromocenium tetracyanoethanide [C_rC_p2^*] [TCNE] by a quasi-one-dimensional alternating-spin model with ferromagnetic exchange interaction. The spin-wave theory is used to discuss the magnetic excitation of the molecular ferromagnet. We obtain the magnetizations corresponding to different external magnetic fields without interchain exchange interaction which is consistent with the experimental results. The formula of the Curie temperature T_c is obtained by using the thermodynamic Green's function method. It is found to be related to the spin of donors, to the intrachain exchange interaction and to the spatial anisotropic parameter. The result obtained by this T_c formula is consistent with the experimental result T_c = 3.6 K for [C_rC_p2^*][TCNE].
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  The Properties of Surface Polaron in the Semi-Infinite Polar Crystal

  LEE Chekman, GU Shiwei, C. C. LAM

  理论物理通讯. 1998, 30(1): 33-40.

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  The effective Hamiltonian and the renormalized mass of surface polaron, where the electron is strongly coupled with the surface optical (SO) phonons but weakly or intermediately coupled with the bulk longit udinal-optical (LO) phonons, were first reviewed. The self-energy and the renormalized mass of the polaron for the polar crystals of potassium iodide, silver chloride and silver bromide are evaluated as a function of the depth Gom the crystal surface. Results of our calculation indicate that the effect of the electron-SO phonon interaction is dominant only within a very small layer from the crystal surface. Its justification awaits further experimental results.
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  The Phase Diagram of Kondo Problem in Luttinger Liquid

  DING Guohui, XU Bowei

  理论物理通讯. 1998, 30(1): 41-44.

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  The problem of Kondo effect in a Luttinger liquid which consists of right-moving, spin-up electrons and left-moving, spin-down electrons is investigated in the bosonized form, and the phase diagram at zero temperature is obtained by a yavefunctional method.
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  Systems Driven by Colored Poisson Noise: Unified Colored Noise Approximation

  CHEN Lihua

  理论物理通讯. 1998, 30(1): 45-48.

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  In this paper, unified colored noise approximation is extended to treat the systems driven by Poisson colored noise χ = ν(χ) + gε_cp(t). We arrive the evolution equation of the probability distribution pi(x, r) and the stationary probability distribution pt (χ, Υ). These equations are valid only if γ(χ,Υ) ≡ γ^-1/2[1 - ΥG(χ)/g(χ)] (G(χ) ≡ v'(χ)g(χ) - v(g)g'(χ)) is large enough (positive) and t >> Υ/γ(χ, Υ), but Υ is not restricted. As an application, we derive the nonlinear relaxation time (NLRT) for the processes driven by Poisson colored noise and evduate the NLRT for the approximative Ginzburg-Landon model under small Υ.
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  Discontinuity and Complex Dynamics of Neural Networks

  ZHOU Changsong, CHEN Tianlun

  理论物理通讯. 1998, 30(1): 49-54.

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  We focus on the discontinuity of a neural network model with diluted and clipped synaptic connections (±l only). The exact evolution rule of the average firing rate becomes a discontinuous piece-wise nonlinear map when very simple functions of dynamical threshold are introduced into the network. Complex dynamics is observed.
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  Correlated Nucleon Pair Model and Microscopic Basis of Interacting Boson

  YANG Liming, LU Dahai

  理论物理通讯. 1998, 30(1): 55-66.

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  An earlier work dealing with low-lying collective states in nuclei is revised and improved. Correlated and independent nucleon S and D pairs properly modified so that they behave approximately like bosons are constructed in terms of which a model space for lowlying collective states is defined, and a microscopic basis for IBM is thus set up. All dynamical variables can also be "bosonized", i.e., expressed in terms of these "bosons" but with statedependent coefficients or operators to incorporate their state dependence in model space.
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  DCC Size Effects on Pion Spectrum Distribution

  ZHANG Qinghui, CHAO Weiqin, GAO Chongshou

  理论物理通讯. 1998, 30(1): 67-72.

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  The effects of two kinds of coherent lengths, the wave packet length of the emitter and the radius of the coherent source, on pion spectrum distribution are studied. It is shown that both coherent lengths can cause abundant pions at low momentum. Observing abundant pions at low momentum may be taken as a signal of DCC effects.
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  Nuclear Gluon Distribution in the Extended χ-Rescaling Model

  DUAN Chungui, HE Zhenmin, LIN Zhongjin, LI Guanglie

  理论物理通讯. 1998, 30(1): 73-76.

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  The extended χ-rescaling model has previously shown to give a good description of the EMC effect. Here, we extend the model to describe the gluon distribution of nucleons bound in nuclei by combining with the nuclear shadowing effect due to the spatial overlap of gluons from neighbouring nucleons in the nucleus in small χ region. The calculated result for G_sn(χ)/G_C(χ) is in good agreement with the experimental data of the New Muon Collaboration (NMC).
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  Phase Formulation and Exact Solutions for the Relativistic Klein-Gordon Field with a Time-Dependent Hamiltonian

  FU Jian, GAO Xiaochun, LI Xinhua, GAO Jun

  理论物理通讯. 1998, 30(1): 77-84.

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  On the basis of the phase formulation, we find the quantum and classical exact solutions and corresponding total phases for the Klein-Gordon (KG) field with a time-dependent Hamiltonian. The total phase includes both the dynamical and geometric phases (Abaronov-Anandan phase). The connection between the quantum and classical solutions is then obtained. From this connection, we discuss the condition under which the geometric phase for the KG field can be defined.
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  Chiral Ring Structure in the N = 2 Superconformal Field Theory Based on the Coset Construction with SU(1,1)/U(1)

  CHEN Yixin, DONG Suchuan

  理论物理通讯. 1998, 30(1): 85-92.

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  In this paper, we carefully analyze the unitarity of the simplest Kazama-Suzuki model based on the noncompact group. The chiral ring structure in this N = 2 theory is clarified. In general, it is infinitely dimensional and innumerable. The primary chiral states belonging to the ring can be constructed by means of the direct products of the highest weight states of the coset SU(1,1)/ U(1) and the scalar representation of U(1) for the fermions. The primary chird and anti-chiral states Jive individually in the positive discrete series D⁺ and negative discrete series D^- of SU(1,1), respectively. With appropriate restrictions, this theory can be regarded as one at the fixed point of a Landau-Ginzburg theory, in which the superpotential is given by S₁₂ in the fourteen exceptional singularities.
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  cb System: Mass Spectra and Decays

  LOU Jizhong, QIN Danhua, DING Yibing, CHAO Kuangta

  理论物理通讯. 1998, 30(1): 93-100.

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  For the cb system, the mass spectra, decay constants, El and M1 transition rates are calculated in a QCD-inspired potential model. Relativistic corrections are taken into account. The El transition rates with relativistic corrections are found to be smaller than those obtained in other models.
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  The Strong Interaction in Chromodynamics Ⅱ

  HU Ning

  理论物理通讯. 1998, 30(1): 101-106.

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  A static soliton solution is obtained from the field equations of chromodynamics. The relativistic wave equation for meson states in which the quark and antiquark interact through the intermediary of this gluon field gives rise. to the same wavefunction and mass spectra obtained before under the independent particle approximation. The calculated values of mass difference of η_c and Ψ/J particles and mass difference of Ψ(3685) and Ψ(3770) due to spin-dependent part of the interaction are in good agreement with the experiment.
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  Finite Temperature Dimensional Regularization to Three-Loop Vacuum Graphs of Massless QED in Arbitrary Gauge

  HOU Defu, LI Jiarong

  理论物理通讯. 1998, 30(1): 107-112.

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  The dimensional regularization is applied to three-loop vacuum graphs in massless QED to evaluate temperature-dependent ultraviolet divergences and infrared divergences in arbitrary covariant gauge. They both are shown to be absent due to cancellations among themselves, and the cancellations are gauge-independent although the individual divergences are gauge-dependent.
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  Solar Neutrino Problem in Seesaw Model

  DONG Fangxiao

  理论物理通讯. 1998, 30(1): 113-116.

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  A specific texture for the Dirac and Majorana mass matrices in the seesaw model leading to a pair of almost degenerate neutrinos is discussed. This texture can be obtained by imposing a global U(1) symmetry. This model could solve the solar neutrino problem through the MSW mechanism and offer the hot component of the dark matter of the universe which requires Σm_vi = 7 eV.
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  Effect of the Spin Fluctuations on the Carrier Thermal Conductivity in High-T_c Oxides

  LOU Ping

  理论物理通讯. 1998, 30(1): 117-120.

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  A theory of the carrier thermal conductivity for electron antiferromagnetic spin fluctuation scattering has been developed and on this basis the experimental results of high-T_c oxides have been interpreted. Our theoretical analysis fits the experimental results excellently and suggests that the antiferromagnetic spin fluctuations affect the carrier thermal conductivity in high-T_c oxides.
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  Path Integral Approach of Quantum Heisenberg Planar Spin Glass Model in the Presencesof Random Field

  MA Yuqiang

  理论物理通讯. 1998, 30(1): 121-124.

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  A quantum version of the site-random Heisenberg planar XY model in a random field is presented in the boson representation. Like classical spherical model in the spin space, the model can be solved exactly within the coherent state path integral-representation. The phase diagram is obtained, and the effects of the randomness and quantum fluctuations on the onset of a spin glass phase are discussed.
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  Phase Operator Theory for an Electron Moving in a Uniform Magnetic Field

  FAN Hongyi, WANG Yihua, FAN Yue

  理论物理通讯. 1998, 30(1): 125-128.

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  We show that the newly found complete and orthonormal representation <λ|, which is constructed in terms of guiding centers and canonical momenta of an electron moving in a uniform magnetic field, also helps us to establish a systematic phase operator theory. The unitary phase operator, interpreted as a quantity canonically conjugated to the electron angular momentum, manifestly exhibits in the <λ| representation its phase behavior. As a byproduct, the phase distribution function, in the correct sense of probability in quantum mechanics, can also be defined by the <λ| representation.
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  A Renormalization Group Study of the Ising Model on a Triangular Lattice with Long-Range Interactions

  FENG Szeshiang, QIU Xijun

  理论物理通讯. 1998, 30(1): 129-132.

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  The critical exponents of the triangular lattice Ising model with long-range interactions γ^-s are calculated by the real space renormalization group. Using the simplest Kadanoff blocks and the lowest approximation of cumulant expansion, it is shown that there exists a finite critical temperature when 4(1 - ㏑2/㏑3) < s < 4.
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  q, s-Taylor's Formula with q, s-Remainder

  SUI Zhenlin, YU Ge, YU Zhaoxian

  理论物理通讯. 1998, 30(1): 133-136.

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  The q, s-Zhyhr's formula with its q, s-remainder by using the q, s-djfferentiation approach is given.
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  The Statistical Interaction and the Bethe Ansatz of the XXZ Chain Corresponding Potts Case

  MI Dong, YANG Fuzhong, HOU Boyuan

  理论物理通讯. 1998, 30(1): 137-140.

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  After introducing briefly the basic concept of statistical interaction, we illustrate it on integrable XXZ chain corresponding Potts case by the Bethe ansatz and point out that the nontrivial part of this statistical interaction comes from the rates of change of phase shifts with respect to momentum.
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  A Note on Algebraically Special, Asymptotically Simple and Empty Spacetime

  KUANG Zhiquan, LAU Yunkau, WU Xiaoning

  理论物理通讯. 1998, 30(1): 141-146.

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  It is proved that subject to certain physically reasonable restrictions on the curvature of spacetime, an algebraically special, asymptotically simple and empty spacetime is necessarily a copy of the Minkowski space. This imposes further requirements a nontrivial asymptotically simple and empty spacetime has to satisfy.
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  Exact Solitary Wave Solutions of the Coupled Nonlinear Scalar Field Equations

  ZHU Yuejin, LOU Senyue

  理论物理通讯. 1998, 30(1): 147-152.

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  Because of the arbitrary property of the singular manifold, the usual singularity analysis can be extended to a different form. Using a nonstandard truncation approach, five special types of exact solution of the coupled nonlinear scalar field equations are obtained.
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  Spin-Dependent Structure Function of Deuteron

  MA Weihsing

  理论物理通讯. 1998, 30(1): 153-156.

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  Based on the relationship between electron deep inelastic scattering and forward virtual photon Compton scattering, and using the information provided by virtual photon absorption on target, we study spin-dependent structure function of deuteron and its correspondingfirst moment, which are expressed by total absorption cross sections of virtual photon. The absorption cross section is determined by helicity amplitudes A_1/2 and A_3/2 which are evaluated in SU(6) quark model with an improved electromagnetic interaction. The method avoids the difficulty for solving nonperturbative QCD which is impossible at present. In general, our theoretical predictions on the first moment and quark polarization in deuteron are in good agreement with data of El43 at SLAC, EMC at CERN and Hermes at DESY.
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  Quantum Dynamical R-Matrix from Fusion

  SONG Xingchang

  理论物理通讯. 1998, 30(1): 157-160.

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  A quantum dynamical R-matrix (QDRM) with three distinct eigenvalues, which is a trigonometric solution of the Germis-Neven-Felder equation, is constructed from the fusion of the simplest 4 × 4 trigonometric QDRM of Hecke type for sl(2).