理论物理通讯

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Calculation of Electronic Structure of Zinc-Blende CdS

Xian-Qi DAI, Wen-Chang LU, Zong-Xian YANG, Shu-Yi WE and Tao ZHANG

理论物理通讯. 1996, 26(3): 257-262.

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The linear-muffin-tin orbital method is used to study the electronic-energy-band structure of zinc-blende CdS. Incorporating the 4d states of Cd into the valence band gives substantially the main-valenceband width, and yields valenceband features in agreement with the experiment. The calculated equilibrium lattice constant is in accord with the measured result. The fundamental band gap is found to be direct at T point and the value is about 1.21 eV. The band structure calculation shows that the present results are in good agreement with experiments and other calculations.

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A Comparative Study on the Electronic Structure and Stability of Ti₈C₁₂ and V₈C₁₂

Chuan-Yun XIAO, Kai-Ming DENG

理论物理通讯. 1996, 26(3): 263-272.

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The electronic structure and stability of dodecahedral Ti₈C₁₂ and V₈C₁₂ clusters are studied and compared with each other by using the discrete-variational local-density functional method. The results show that there exists a nearly-rigid-band-shift rela tion between the electronic structures for the two clusters and that the corresponding bands for them have similar bonding character. Therefore, both clusters can be stable for similar reasons. The results also indicate that there exist two types of charge transfers for both clusters, in which the electrons are found to accumulate to the Ti3d (V3d) and C2p orbitals so that the p-d bonding between the C and Ti (V) atoms is strengthened. Based on the above results, the influence of the charge on the electronic structure and stability of both dusters is examined. FinaUy, the ground-state electronic configurations are obtained for both clusters in the neutral, cationic and anionic charge states. The ground states for the cationic Ti₈C₁₂ and VeCn clusters are found to be nondegenerate. The dodecahedral structures for these two clusters are thus remarkably stable. The rest clusters, i.e., neutral and anionic Ti₈C₁₂ and V₈C₁₂ clusters, have degenerate ground state, and therefore, their structures are expected to undergo Jahn-TeUer distortion further.

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Exactly Solved Fermion-Boson Model for Heavy-Fermion Alloys

Wu-Ming LIU, Hong-Wei ZHAO, Zhu YU, Fu-Cho PU

理论物理通讯. 1996, 26(3): 273-278.

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The exact eigenstates of the Hamiltonian of the fermion-boson model for heavy-fermion alloys are constructed by using the Bethe ansatz. The Bethe ansatz equations are obtained from the periodic boundary conditions.

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The Influence of Lanthanum on Slow Component in the Scintillation Light of BaF₂

Mu GU, Ling-Yan CHEN, Qing LI and Xiang WU

理论物理通讯. 1996, 26(3): 279-282.

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The electronic structures of pure BaF₂ crystal and lanthanum doped BaF₂ crystal were calculated in a self-consistent molecular-cluster model. The cluster was embedded in the crystal lattice and the entire system was treated iteratively in the Hartree-Fock-Slater localdensity theory. As lanthanum doped BaF₂ is concerned, the obtained results revealed that the F_i^- which is introduced by the lanthanum may contribute to the suppression of the slow component in the scintillation light of BaF₂ crystal.

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The Perturbation Approxirnation of the Mean First-Passage Time for Nonlinear Non-Markovian Continuous Processes

Ming IYANG, Da-Jin WU and Li CAO, Zai-Guang LI

理论物理通讯. 1996, 26(3): 283-288.

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In this paper, we generalize the method which is presented by J. Masoliver [J. Masoliver,Phys. Rev. A45 (1992) 22561 to calculate the mean first-passage time (MFPT) for the systems driven by nonlinear non-Markovian continuous noises. We present the perturbation approximation method for treating the near-free systems and the ones that can be transformed into near-free systems, and we give the general calculation formula for the zero-order and first-order approximations of the MFPT. We apply the method to three typical examples with rectangular temporal distribution in detail. The first is about the nonlinear free process; the second is about the stochastic process with square nonlinear drift; the third is about the stochastic process driven by multiplicative and additive noises altogether.

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Bogoliubov Matrices in Thermal Field Theory

Hong-Hua XU

理论物理通讯. 1996, 26(3): 289-294.

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It is found that Bogoliubov matrices introduced in thermo field dynamics can be generally derived for an arbitrary value of the time-path parameter a, 0 ≤ α ≤ β, by the closed-time path approach in a natural and simple way. Based on the generalized Bogoliubov matrices the meaning of widely believed a-independence of thermal field theory is discussed.'

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Solutions to Braid Group, Yang-Baxter Equation and Integrable Fermion Systems

H. YAN and J. ZHANG

理论物理通讯. 1996, 26(3): 295-304.

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Braid group representations are found in ferrnion systems in one space dimension. Explicit baxterization is performed to find corresponding new trigonometric solu tions of Yang-Baxter equation. The quantum algebra structures implied in the new solutions are discovered. Algebraic Bethe ansatz method is applied to solving these systems. The relationships between these fermion systems and polaron model, spin-1/2 Heisenberg spin chain are discussed.

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Irreducible Representations of the Quantum Group U_q(m + n) in U_q(m)⊕ Uq(n) Basis

Feng PAN

理论物理通讯. 1996, 26(3): 305-310.

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Irreducible represen tations of U_q(m + n) in U_q(m) ⊕ U_q(n) basis are discussed. The noncanonical basis of U_q(m + n) are expanded in terms of its canonical basis. The expansion coefficients or subduction coefficients of U_q (m + n)↓ U_q(m) ⊕ U_q(n) are derived from the subduction coefficients of Hecke algebras.

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Symmetry Algebras and Group Invariant Solutions of the Kawamoto-Type Equations

Sen-Yue LOU

理论物理通讯. 1996, 26(3): 311-318.

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Starting from 10 sets of symmetries of the Kawamoto equation, one can get 10 hierarchies of corresponding integrable models. These hierarchies possess the same recursion operator but they do not possess common symmetry structure. Only two hierarchies related to the kernel ofinverse recursion operators have the same time-independent symmetry structure as that of the Kawamoto equation. However, the symmetry algebras of the other eight hierarchies are only isomorphic to some subalgebras of that of the Kawamoto equation. Especially, three hierarchies of them possess six sets of time-independent noncommute symmetries while the other five hierarchies possess only four sets of time-independent but commute symmetries.Only one set of time-dependent symmetries for all ten hierarchies is obtained. Using the point symmetry algebra of the Kawamoto equation, various new complex group-invariant solutions (similarity reductions) of the Kawamoto equation are also given.

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The Wavefunctions of the Composite Particle Representation Theory in s-d Shells

Guang-Zhou LIU, Ke-Xie WANG

理论物理通讯. 1996, 26(3): 319-326.

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The wavefunctions of the composite particle representation theory (CPRT) are composed of two parts, the fermion part and the composite particle part. The CPRT wavefunction's fermion part is iden tical to the shell model (SM) wavefunction. The composite particle degrees of freedom exist in the O's form, so a criterion to identify physical states is presented. The formulas of the CPRT wavefunction's nomalization are also presented explicitly. Calculating the normalizations is another effective way to identify physical states. As a test for CPRT the ground state's CPRT wavefunctions for the s-d shell nuclei ²⁰O and ²⁰F as well as their normalizations are calculated. These strict numerical results show that the composite particle representation is equivalent to the conventional representation in quantum mechanics.

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A Variational Approach for Hadronic Properties in NJL Model

H. GUO

理论物理通讯. 1996, 26(3): 327-332.

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We develop a variational approach for the Nambu-Jona-Lasinio (NJL) model with explicit chiral symmetry breaking and compute the constituent quark mass, the pion decay constant and the vacuum condensate. For a simple ansatz for the hadronic wavefunction, we also analyze the effects of the current quark mass and the ultraviolet cutoff on the static properties of hadrons.

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Pion Inelastic Scattering from ¹⁵²Sm with Excitation to 3₁^- State

Yu-Xin LIU, Yu-Shun ZHANG, En-Guang ZHAO, Hong-Zhou SUN

理论物理通讯. 1996, 26(3): 333-338.

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The description of the medium energy pion-nucleus inelastic scattering which excites the target from the ground state to a negative parity state is discussed in the approach of combining Eikonal approximation with spdf Interacting Boson Model. The calculated differential cross sections of the 180 MeV π^± - ¹⁵²Sm scattering with excitation from 0₁⁺ to 3₁^- state and the deformation parameter of the 3₁^- state agree with experimental data quite well. It indicates that the 3₁^- state of ¹⁵²Sm may probably be an octupole vibrational state. And the effect of mu1 tiple scattering is shown to be important in the scattering process.

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Study of Gluon Transport Equations by the Multiple Time-Scale Met hod and Calculation of the Nonlinear Landau Damping Rate for Plasmons

Xiao-Fei ZHANG and Jia-Rong LI

理论物理通讯. 1996, 26(3): 339-346.

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The transport equations for gluon plasma are studied beyond the linear approximation by the multiple time-scale method. And the nonlinear Landau damping rate for the long-wavelength plasmon in gluon plasma is calculated.

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Heavy Quark Limit of Weak Transition Form Factors in a Light-Cone Constituent Quark Model

Xiao-Ming XU

理论物理通讯. 1996, 26(3): 347-354.

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In the light-cone constituent quark model, the wavefunction for Λ_b⁰ or Λ_c⁺ with three quarks is reduced to a wavefunction for the heavy-quark-diquark picture by assuming that the two light quarks forming a diquark are in comoving. A heavy quark (or diquark) distribution amplitude is obtained. While form factors of weak transition Λ_b → Λ,ev are calculated in the finite mass case, a hadronic-size-dependen t form of Isgur- Wise function is obtained in the m_Q → ∞ limit.

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The Invariant-Related Unitary Transformation Method and the Evolution of Quantum Scalar Field in Robertson-Walker Flat spacetime

Xiao-Chun GAO, Jun GAO, Jian FU and Lan WANG

理论物理通讯. 1996, 26(3): 355-362.

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On the basis of the generalized invariant formulation, the invariant-related unitary transformation method is developed and used to study the evolution of a quantum scalar field in Robertson-Walker flat spacetime. We first solve the functional Schrödinger equation for a free scalar field and obtain the exact solutions, of which the 'ground-state' solution possesses isotropy and homogeneity automatically We then investigate the way of extending the method to treat the case in which there is a high-order perturbative self-in teraction.

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Flux of Scalar Neutrino Dark Matter

Xue-Qian LI, Xin-He MENG, Hua-Gang YAN, Wan-Yun ZHAO

理论物理通讯. 1996, 26(3): 363-368.

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Recently the exotic event observed at the Yunnan Cosmic Ray Station (YCRS) is reinterpreted as a neutral supersymmetric (SUSY) particle bombarding on proton to produce a charged SUSY particle which decays afterwards. The kinematics analysis determines the lower bounds of its mass and lifetime. Taking this bounds as inputs and following recent literatures to assume the scalar neutrino (sneutrino) as the main constituent of the cold SUSY dark matter, we calculate the flux of sneutrino at the earth detector in terms of the standard rate equation of cosmic matter.

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The Complete Integrability of Variable-Coefficient Burgers Equations

Chang-Zheng QU, Ai-Qin WANG

理论物理通讯. 1996, 26(3): 369-372.

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In this paper, we discuss the complete integrability and allowed transformations for the variablecoefficient Burgers (VCB) equations which come from shock waves and sound waves. It is shown that certain conditions for which the variablecoefficient functions must satisfy for the VCB equations to pass the PainlevC tests for complete integrability are exactly the same as those in order that equations may be transformed into the Burgers equation.

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Nonlocal Lie-Backlund Symmetries and Solitary Wave I Solutions of the General KdV and mKdV Equations

Jie-Fang ZHANG

理论物理通讯. 1996, 26(3): 373-376.

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In this paper, three sets of high-order nonlocal Olver symmetries are obtained from a special nonlocal Lie-Backlund symmetry of the general KdV and general mKdV equation. The soliton solutions of these models can be also obtained from the finite Lie-Backlund transformations.

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Covariant Description of the A in Relativistic Transport Theory

Guang-Jun MAO, Zhu-Xia LI and Yi-Zhong ZHUO, Zi-Qiang YU

理论物理通讯. 1996, 26(3): 377-380.

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We have derived the relativistic Boltzmann-Uehling-Uhlenbeck equation for delta distribution function based on the same effective Lagrangian in which we derive the equation of nucleon. The equations of nucleon and delta are coupled with each other through self-energy terms and should be solved simultaneously.

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Some Theoretical Considerations on Heavy Quarkonium systems

S. F. TUAN

理论物理通讯. 1996, 26(3): 381-384.

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There is a recent revival of experimental and theoretical interest in the heavy quarkonia systems with the experimental hint of a ¹P₁ state in the charmonium system. In the future, CLEO H will run on the γ(3S) resonance and accumulate as much as 2.1 × 10⁶ γ(3S) decays. We discuss here the theoretical implications for these systems. Topics considered are the n parameter and S-D mixing in heavy quarkonia, γ(3S) → γ(¹P₁)ππ decay rate and spectrum, the predicted rate for γ(1D) → γ(1S) ππ, the problem of the production of spin-singlet states from hadronic transitions of c armonia and the puzzle of the missing φ(¹P₁) → J/φπ⁺π^- decay.

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1996年, 第26卷, 第3期　
刊出日期：1996-10-30

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选择文件类型/文献管理软件名称

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1996年, 第26卷, 第3期 刊出日期：1996-10-30

1996年, 第26卷, 第3期　
刊出日期：1996-10-30