1999年, 第31卷, 第2期　
刊出日期：1999-03-15

  

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  The Vibrational Spectrum of Methane in an Extended Boson-Realization Model

  XIE Mi, HOU Xiwen, DONG Shihai, MA Zhongqi

  理论物理通讯. 1999, 31(2): 161-168.

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  The vibrational spectrum of methane, including both stretching and bending vibrations, is calculated in terms of an extended boson-realization model, by taking into account the interactions between vibrations up to the fourth order. The problem of removal of spurious states is discussed in detail. The term number in the Hamiltonian increases very fast as the interaction order increases. When the spurious states are removed from the configuration space, the effective Hamiltonian is not unique. We find a method to greatly simplify the T_d invariant Hamiltonian without any error. Fitting 45 experimental data with the Hamiltonian gives a root-mean-square energy deviation 3.96 cm^-1.
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  High-Lying Vibrational Spectrum of Ammonia via Nonlinear Quantum Theory

  CHEN Xiangrong, GOU Qingquan, PANG Xiaofeng, CHENG Yan

  理论物理通讯. 1999, 31(2): 169-174.

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  We introduce a simple three-parameter model in nonlinear quantum theory-the discrete self-trapping equation to describe the stretching spectrum of ammonia at highlying vibrational states. The model calculations appear to describe the data well. These results obtained are conducive to researching the quantum chaotic manner and the multiphoton processes and isotope separation by multiphoton dissociation of ammonia molecular system.
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  Exact Solution of a Many-Level Atom Interacting with a Monochromatic Field Without Rotating Wave Approximation

  FENG Mang, FANG Ximing, SHI Lei, DUAN Yiwu, ZHU Xiwen

  理论物理通讯. 1999, 31(2): 175-180.

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  In the coherent-state representation, the technique applied to the Jaynes-Cummings (JC) model in the absence of rotating wave approximation (RWA) is extended to the treatment of a many-level atom interacting with a monochromatic field. Some general results are presented.
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  The Bilinear and Intrinsic Biquadratic Coupling in Magnetic Metallic Trilayers

  SHEN Rui, XIAO Mingwen, LI Zhengzhong

  理论物理通讯. 1999, 31(2): 181-188.

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  We find the exact Green's functions of the Anderson s-d mixing model for magnetic trilayers with arbitrary spin canting angle between two ferromagnetic layers within the rneanfield theory of the on-site Coulomb repulsion. A bilinear exchange coupling and an intrinsic biquadratic coupling which does not vanish in the limit of flat interfaces is obtained by those Green's functions. It is shown that both of these couplings oscillate in the experimental range of the spacer thickness only when the s-d mixing is strong enough. When the mixing strength is large enough one finds that the oscillation period of the intrinsic biquadratic term is equal to half of the corresponding one for the bilinear term. We also find that the temperature dependence of those interlayer couplings is considerably enhanced with the decrease of the Hubbard coupling. It is also shown that the biquadratic coupling falls off much more rapidly with increasing temperature than the bilinear one.
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  Study on Two Generalized FK Models

  XU Aiguo, XU Haibo, WANG Guangrui, CHEN Shigang

  理论物理通讯. 1999, 31(2): 189-198.

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  We study two generalized FK models. Each describes a chain of atoms connected by double-well interactions in the presence of a perturbed sinusoidal external potential. The phase diagram varies with the period of the external potential D and with the amplitude of the perturbation ε. Some novel and complex phase structures are found. There are two threshold values of D for each model, which equal the distance and two times of the distance between the two wells of the interatomic interactions, respectively. Within different interval of D, the phase diagrams exhibit different behaviors.
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  Self-consistent Mean-Field Theory of Two-Dimensional Anisotropic Heisenberg Antiferrornagnet

  SONG Yun, FENG Shiping, MA Benkun

  理论物理通讯. 1999, 31(2): 199-204.

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  A self-consistent mean-field theory for the two-dimensional spin-1/2 XY-Heisenberg an tiferromagnet without long-range-order is developed. Within this theoretical framework, the thermodynamic properties, such as the internal energy, specific heat and parallel susceptibility, are discussed, and the results are in rough agreement with the numerical simulation.
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  The Effect of Nonmagnetic Doping on the d-Wave Heavy Fermion Superconductivity

  SHI Daning, LI Zhengzhong

  理论物理通讯. 1999, 31(2): 205-210.

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  In the present article, the use of slave-boson mean-field theory of the extended Anderson lattice model has been generalized to the Nambu space. The Green's functions of heavy fermion superconductors (HFS) have been obtained. The high sensitivity of the d-wave pairing HFS to the nonmagnetic impurities has been studied. The obtained results are in good agreement with the recent experiments on HFS.
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  Bias Dependence in Spin-Polarized Tunneling of Ferromagnet/Ferromagnetic Insulator (Semiconductor)/Ferromagnet Junctions

  LI Yun, LI Bozang, DAI Daosheng

  理论物理通讯. 1999, 31(2): 211-214.

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  Based on the nearly-free-electron approximation, the bias dependencies of electron transport properties of ferromagnet/ferromagnetic insulator (semiconductor)/ferromagnet junctions have been studied. Resonances appear in electron transmission probability. These resonances cause oscillations in the zero-temperature tunnel current and the resonances occur in tunnel conductance. Tunnel magnetoresistance (TMR) is an oscillatory function of bias. The TMR can reach a value as high as 100%. The bins dependencies of electron transport properties relate to the magnetic configurations of the junctions.
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  Study of Spin-One Heisenberg Model with Single-Ion Anisotropy by variational Curnulant Expansion

  WANG Qing, CHEN Tianlun

  理论物理通讯. 1999, 31(2): 215-218.

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  We study spin-one Heiseibergm odel with single-yon anisotropy for both easy-axis and easy-plane cases. Critical temperatures are obtained for different 3-dimensional lattices. Choice of trial action S₀ is discussed.
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  Replicon Modes in the Renormalization Group with Replica Symmetry Breaking

  WU Xintian

  理论物理通讯. 1999, 31(2): 219-222.

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  Abstract The renormalization group with replica symmetry (RSB) breaking is studied for the disordered ferromagnets. The ε-expansion (ε= 4-D, D is the spatial dimension) is used. For fixed points with step-like RSB structufe replicon eigqnvalpes are defined to describe the stability of the fixed points with respect to the continuous lESB perturbation.It is shown that this metliod can be generalized to the cases in which the number of the steps in the step-like RSB structure ahd the order of expansion are arbitrary.
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  Linearly-Independent Quantum States Can Be Cloned by a Unitary-Reduct ion Operation

  DUAN Luming, GUO Guangcan

  理论物理通讯. 1999, 31(2): 223-226.

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  The famous quantum no-cloning theorem [Nature 299(1952)802] forbids replication of an arbitrary unknown quantum state. But it leaves open the follorc-ing question: If the state is not completely arbitrary, but secretly chosen from a certain set $ = {|Ψ₁>,| Ψ₂>,...,|Ψ_n>}, whether is the cloning possible? It is proved that the states from the set $ = {|Ψ₁>,| Ψ₂>,...,|Ψ_n>} can be faithfully cloned by a general unitary-reduction operation in a probabilistic fashion if and only if |Ψ₁>,| Ψ₂>,... and |Ψ_n> are linearly-independent.
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  Various Re-ordering Expressions of General Exponential Quadratic Operators in Mutli-Mode Boson System

  XU Xiuwei, ZHANG Yongde

  理论物理通讯. 1999, 31(2): 227-232.

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  In this paper, we give various explicit expressions and transform equalities among usual, normal and anti-normal orderings for the exponential inhomogeneous quadratic (EIQ) operators and their inverse operators in multi-mode boson systems.
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  Algebraic Expressions for Some SO(N) Racah Coefficients for the Two-Rowed Irreducible Representations

  RUAN Dong, SUN Hongzhou

  理论物理通讯. 1999, 31(2): 233-238.

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  In this paper the algebraic expressions for SO(N) Racah coefficients involving the coupling of three irreducible representations (irreps)(10),(m_l m₂ 0) and (10) are given using the building-up process.
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  Exact Solitons of a d-Dimensional Discrete Modified KdV Equation

  HUANG Yanzhao, XIAO Yi

  理论物理通讯. 1999, 31(2): 239-242.

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  We show by using the real exponential approach that the d-dimensional discrete modified KdV equation has more general exact solitary wave solutions than the known bright soliton and kink solutions. Depending on the values of the parameters, the new solutions can describe both bright and dark solitary waves.
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  Quasielastic Electron-Deuteron Scattering in a Hybrid Quark-Hadron Model

  CHENG Tansheng, LI Gang, LU Lanchun

  理论物理通讯. 1999, 31(2): 243-250.

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  We study the effects of six-quark cluster and meson exchange current on quasielastic electron-deuteron scattering, using the hybrid quark-hadron model incorporating the contribution of the isoscalar meson exchange current. Our results indicate. that the final state interaction, isoscalar and isovector meson exchange currents, and six-quark cluster contribute few to the quasielastic peak. However, they affect the extracted neutron electromagnetic form factors to some extent.
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  Bose-Einstein Correlation of Kaon Pairs from Heavy-Ion Collisions at CERN Energy

  ZHENG Yuming, CHU Zili, Osamu Miyamura, Kenji Kumagai

  理论物理通讯. 1999, 31(2): 251-254.

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  The Bose-Einstein correlation of kaons from 160A GeV/c Pb + Pb collisions is analyzed within an event generator UR4SiMA. The theoretical results are in agreement with the preliminary data of NA44.
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  The Structure of S Pair in Collective States (Ⅰ)

  LU Dahai, YANG Liming

  理论物理通讯. 1999, 31(2): 255-260.

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  A new S pair and seniority particle operator used to overcome the difficulties due to seniority mixing are defined in collective motion of nuclei. The structure amplitude of S pair is determined in a self-consistent manner.
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  The Structure of S Pair in Collective States (Ⅱ)

  LU Dahai

  理论物理通讯. 1999, 31(2): 261-264.

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  Comparison between states composed of the newly defined S pairs used for dealing with seniority mixing problem and those made from the usual S pairs is given.
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  An ?-Deformed Virasoro Algebra as Hidden Symmetry of the Restricted sine-Gordon Model

  HOU Boyu, YANG Wenli

  理论物理通讯. 1999, 31(2): 265-270.

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  As the Yangian double with center, which is deformed from affine algebra by the additive loop parameter ?, we get the commutation relation and the bosonization of quantum ?-deformed Virasoro algebra. The corresponding Miura transformation, the associated screening operators and the BRST charge have been studied. Moreover, we also construct the bosonization for type Ⅰ and type Ⅱ intertwiner vertex operators. Finally, we show that the commutation relations of these vertex operators in the case of p^′ = γ, p = γ - 1 and ? = π actually give the exact scattering matrix of the restricted sine-Gordon model.
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  Cltzster Effect in e⁺ e^- Annihilation

  GAO Chongshou, CHAO Weiqing, HE Bin

  理论物理通讯. 1999, 31(2): 271-276.

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  Based on the picture of hadron cluster, some parameters about cluster are obtained in e⁺ e^- annihilation and it is found that the intermittent behavior in e⁺ e^- annihilation is closely related with short-range correlation from hadron cluster.
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  Rare Decays B→K^(*) e⁺ e^- Test of the Standard Model

  LU Gongru, XIONG Zhaohua, CAO Yigang, HUANG Jinshu

  理论物理通讯. 1999, 31(2): 277-284.

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  The exclusive B→K^(*) e⁺ e^- decays are studied in the topcolor-assisted technicolor model and in the minimal technicolor model. We find that the angular distribution and the dilepton mass distribution in B→K^(*) e⁺ e^- which can be reliably predicted in the large dilepton mass region, are very sensitive to the actual form of the new interaction. This provides a good test to physics beyond the standard model.
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  The Development of Dirac's Symbolic Method by Virtue the IWOP Technique

  FAN Hongyi

  理论物理通讯. 1999, 31(2): 285-290.

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  Dirac expected that his symbolic method (q-number theory) which could express the physical law in neat and concise way would probably get developed. In this paper, we show that the technique of integration within an ordered product of operators can fashion Dirac's symbolic method and develop representation theory and transformation theory of quantum mechanics.
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  Topological Kinks in φ²ⁿ Field Theories and Low Energy Excited States

  WU Juhao, LIN X iaodong, LIU Yueran, XU Senlin, FENG Mang, WANG Kelin

  理论物理通讯. 1999, 31(2): 291-296.

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  The static kinks and their low energy excited states in scalar field theories with V[φ]= -(1/2)m²φ² + gφ²ⁿ/2n are studied in a function-series method. We give a universal formal solution, and a universal approach to find the low energy excited states as well. Excellent agreement between the FS solution and the exact answer is found. This confirms our predicted results of the energies of the excited quantum states by considering small oscillations about the kink motion.
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  A Method for Avoiding the Divergence Difficulties of Quant urn Mechanics

  HAI Wenhua

  理论物理通讯. 1999, 31(2): 297-300.

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  Abstract High-ordered correction of wavefunction for Schrodinger equation with one dimensional potential V(x) and interaction Hamiltonian H′(x) has been found by introducing a new particular solution φ_Ek⁽⁰⁾ for H′(z) = 0. Convergence conditions of the rvavefunction lead to the formulas of energy corrections and scattering amplitudes. It is shown that the result can avoid some divergence difficulties of quantum mechanics.
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  Josephson-Like Effects in the Mesoscopic Electric Circuit

  CHEN Bin, CHEN Lijun, HAN Rushan

  理论物理通讯. 1999, 31(2): 301-304.

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  Abstract The quantum theory for mesoscopic electric circuit with charge discreteness is briefly described. The Schrodinger equation of the mesoscopic electric circuit with external source which is a time function has been proposed. The Josephson-like effects in the mesoscopic electric circuit have been addressed.
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  RAA Electron-Phonon Interaction Cannot Support High T_C in YBaCuO

  HE Lixin, CHENG Geng

  理论物理通讯. 1999, 31(2): 305-308.

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  The e-ph interaction in YBaCuO is calculated and the nonlinear Eliashberg equation is solved by the newly introduced bifurcation theory and parameter imbedding method. The transition temperature is low from the traditional (RA.4) e-ph model. The cause of some authors' improper high T_C result is discussed.
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  Soliton Transmission and Reflection Due to the Inhomogeneity

  DUAN Wenshan

  理论物理通讯. 1999, 31(2): 309-312.

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  A new approach to nonlinear wave in one-dimensional discontinuous fluid-filled elastic tube is presented. As-a model, an elastic tube which has a discontinuity of radius, thickness and Young's modulus is considered. The incident, reffe cted and transmitted waves are described by KdV equations. The reflected and transmitted waves are constructed from incident wave analytically. Fission and reflection of a soliton due to the discontinuity are explicitly shown in the lowest order
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  New Properties of Systematics for the Non-Yrast Bands in Nuclei

  ZHAO Yumin

  理论物理通讯. 1999, 31(2): 313-316.

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  Within the improved valence correlation scheme, it is revealed that an elegant systematics exists for the non-yrast bands of even-even nuclei using the IBM-2 effective boson numbers.
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  A New Explanation for e⁺e^- Puzzle in Heavy-Ion Collisions

  TANG Peng, ZHANG Jianwei, WANG Chengshing

  理论物理通讯. 1999, 31(2): 317-320.

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  A dielectric model for the QED vacuum in a strong nuclear environment is proposed to explain the e⁺e^- puzzle in heavy-ion collisions, the agreement with experiment is satisfactory. New experiment is suggested from this model.