1996年, 第26卷, 第4期　
刊出日期：1996-12-15

  

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  Effect of Both Adiabatic and Non-Adiabatic Atomic Motion in Generalized JC Model

  Cheng WANG, Li ZHANG, Chang-Pu SUN

  理论物理通讯. 1996, 26(4): 385-388.

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  This paper deals with the dynamic behavior of atom-evolu tion affected by motion of atomic mass-center in a high Q cavity. A generalized JC model is treated on this problem. The adia-batic condition is presented also in an explicit form. The time-evolution of the wavefunction is obtained, via quantum high-order adiabatic approximation (HOAA). Then the transition probability and average energetic distributions of each part at any time are discussed.
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  Algebraic Bethe Ansatz for Generalized t-J Model

  Rui-Hong YUE, Zhao-Ming QIU

  理论物理通讯. 1996, 26(4): 389-400.

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  In this paper we show the generalized t-J model with periodic condition integrable. By using the QISM, we exactly diagonalize the model in three different backgrounds. The energy spectrum and Bethe ansatz equations are obtained.
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  Additional Long-Range Interactions on Diamond-Type Hierarchical Lattices

  Song LI, Z. R. YANG

  理论物理通讯. 1996, 26(4): 401-406.

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  The Ising model with additional next-nearest neighbour (n.n.n.) interactions in generator of diamond-type hierarchical lattice is studied. It is found that phase transition occurs only when the nearest neighbour (n.n.) interaction K₁ and n.n.n. interaction K₂ fulfils a certain relation and the universal class of phase transition is not changed by the long-range interactions.
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  The Novel Properties of the Environment in Independent Oscillator Model

  Jian-Zhong GU, Xi-Zhen WU, Yi-Zhong ZHUO

  理论物理通讯. 1996, 26(4): 407-412.

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  The novel properties of the environment are found in independent oscillator model. 1) If the initial state of the composite system lies in thermal equilibrium, then the environment is equipartition of energy, which, however, is moving with the system. 2) When the environment is in thermal equilibrium, but the system deviates from it at the beginning, the environment is no longer equipartition of energy, but which still moves with the system. These properties are quite different from those of the collection of oscillators discussed by Ford et al. (see Ref. [9])
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  On the Difference and Similarity Between Elastic Scatterings of Ne + C and O + O¹

  Cheng-Qun GAO

  理论物理通讯. 1996, 26(4): 413-420.

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  Based on the LCNO model with double alpha transfer and on the optical model, the experimental excitation functions and the angular distributions of ²⁰Ne + ¹²C and ¹⁶O + ¹⁶O elastic scatterings are respectively reproduced by using approximately equal parameters of optical potentials. The difference and the similarity exhibited in the elastic scattering excitation functions of these two systems are naturally explained.
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  Studies of In-Medium Nucleon-Nucleon Collision Cross Section in the Nonrelativistic Energy Region

  Xiang-Hua ZENG, Ling-Xiao GE

  理论物理通讯. 1996, 26(4): 421-424.

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  At nonrelativistic energy region, by using Skyrme interaction, nucleon-nucleon collision cross sections in medium and their relations with densities and energies have been studied. It is found that under PauLi correction, nucleon-nucleon collision cross section in medium is larger than free nucieon-nucleon collision cross section.
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  Quark Bomding Potential and Debye Screening Length

  Bo LIU, Yu-Bing DONG

  理论物理通讯. 1996, 26(4): 425-432.

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  The binding and dissolution for the cc and bb bound states are studied by using different quark binding potentials in a nonrelativistic approximation. We calculate the critical value of the screening length by considering the Debye screening effect. The critical value r_D^c of the Debye screening length is highly sensitive to the form of the quark binding potential. We also estimate the critical temperature T_c of medium. The influence of the form of the quark binding potentials on dissolution for cc and bb bound states is discussed and compared to the previous results.
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  Effect of Gaussian Potential on the Differential Cross Sections of Alpha Transfer Reactions

  A. A. Farra

  理论物理通讯. 1996, 26(4): 433-438.

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  The differential cross sections of different alpha transfer reactions have been investigated by using the exact finite-range DWBA calculations. The double-folding density-dependent model is used for the real and imaginary nucleus-nucleus potential in the initial and final channels. The effective nucleon-nucleon interaction is assumed to be the double-Gaussian potential. The Yukawa interaction is found reasonable and exhibits a slight better agreement at energies above the barrier region. The obtained values of the extracted normalization factors are reasonable.
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  New Methods for Computer Simulations of the Scalar Models with Dynamical Fermions

  Xiang-Qian LUO

  理论物理通讯. 1996, 26(4): 439-448.

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  The fermion-gauge-scalar models exhibit interesting chiral phase structure. To study the properties of the critical phenomena on computer, we further develop some new efficient numerical methods applicable to the chiral limit where the conventional algorithms cannot reach.
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  Production Rate of D_s⁺D_s^- at φ(4030)

  Kuang-Ta CHAO, Yi-Bing DING

  理论物理通讯. 1996, 26(4): 449-454.

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  By using a generalized relativistic quark pair creation model (QPCM), the hadronic decay processes of φ(4030), assigned as the 3S state of cc, are investigated. The relative rates of φ(4030) → DD, DD^*+DD^*, D^*D^*,and in particular D_s⁺D_s^- are calculated and compared with data. The nodes of the radially excited wavefunctions of charmonium states are found to be significant for these decay processes. Considering the SU(3) suppression factor of ~3 for the s quark pair creation relative to the u and d quarks, we obtain σ(e⁺e^- → φ4(4030) → D_s⁺D_s^-) ~ 0.9 nb.
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  CP Asymmetry in Top Quark-Pair Production via Photon Fusion (1): for Unpolarized Photon Beams

  Wen-Gan MA, Chao-Hsi CHANG, Xue-Qian LI, Zeng-Hui YU, Liang HAN

  理论物理通讯. 1996, 26(4): 455-460.

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  The possibility to investigate CP violation in top pair production via unpolarized photon beam collisions is studied. Here we mainly focus on the CP asymmetry effects which arise in two Higgs doublet extensions of the minimal standard model. We point out that the resultant CP asymmetry up to the level of an order of 10^-3 may be expected.
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  Space-Charge Effect on Residual Energy Under Intense Ultrashort Pulse Laser

  Shi-Gang CHEN, You-Qin WANG, XiaeBo NIE

  理论物理通讯. 1996, 26(4): 461-468.

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  Can the spacecharge effect reduce the above-threshold-ionization (ATI) energy? This problem is analyzed by using the technique of multiple-time-scale perturbation. As the optical frequency is much larger than the plasma frequency, the space-charge effect is then reduced to the ponderomotive effect. It is found that the ponderornotive effect on residual energy is great as half plasma period is larger than pulse length, however, it cannot reduce the AT1 energy over the whole density range. The relevant experiments are analyzed. Their results support our conclusions. Finally, it is pointed out that for a given pulse laser there may be a density range available for optical field ionization x-ray laser over which only the AT1 heating plays role.
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  Sonic Point Instability in the Causally Limited Viscosity and Magnetized Accretion Disc

  Pi-Bo YANG, Lan-Tian YANG, Shao-Ping WU, Xue-Bing WU

  理论物理通讯. 1996, 26(4): 469-474.

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  The stability of sonic point in an isothermal accretion disc is examined for the case in which the causally limited viscosity and magnetic fields coexist. The results show that the sonic point is a saddle and stable against small amplitude perturbations. Finally, we discuss these results.
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  The Evolution Feature of Chirp-Dark Soliton in Single-Mode Fiber

  Wei-Ping ZHONG, Ze SHI, Guo-Ding CHEN

  理论物理通讯. 1996, 26(4): 475-478.

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  The evolution feature of the injected initial-chirp tanh-dark soliton in single-mode fiber is studied in this paper. We analyze the evolution of amplitude, pulse width, frequency chirp and center position shift of dark soliton along with the variation of propagation distance, primarily using Lagrange-Euler's formula and taking the high-order dispersion as perturbation. The results show that the amplitude and pulse width of chirp-dark soliton are all oscillating around a certain critical distance in ideal fiber (β = 0), and the high-order dispersion conduces to generate the asymptotic dark soliton.
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  Some Addenda About the General Formula of Normal Product Calculation for Boson Exponential Quadratic Operators

  Jian-Wei PAN, Yong-De ZHANG, Xiang-Bin WANG, Lei MA

  理论物理通讯. 1996, 26(4): 479-482.

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  In this paper, we studied the general formula of normal product calculation for boson exponential quadratic operators (EQO) which is first obtained by WANG et al. (J. Phys. A: Math. Gen. 27 (1994) 6563]. It is shown that the boundness of boson EQO will result in a restriction on the applicable bounds of this formula. According to the restriction condition, the conclusion about unity operator given by MA et al. [Commun. Theor. Phys. (Beijing,China) 21 (1994) 119] should be made some corresponding corrections. At last, we extended this formula to the case of fermion for the convenience of later applications.
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  A New Class of Representations of Braid Groups

  Dian-Min TONG, Shan-De YANG, Zhong-Qi MA

  理论物理通讯. 1996, 26(4): 483-486.

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  In this letter, a new class of represen tations of the braid groups B_N, I_i-1⊕ T ⊕ I_N-i-1 is constructed. It is proved that those represen tations contain three kinds of irreducible representations: the trivial (identity) one, the Burau one, and a new N-dimensional one. The explicit form of the N-dimensional irreducible representation of the braid group B_N is given.
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  On the Dromion Solutions of a (2+l)-Dimensional KdV-Type Equation

  Sen-Yue LOU

  理论物理通讯. 1996, 26(4): 487-490.

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  A general curve soliton which is finite on a curved line and localized apart from the curve for a (2+1)-dimensional KdV-type equation is found. For the KdV-type equation, we find that the dromion solutions can be obtained not only by two perpendicular line solitons, two nonperpendicular (with one is parallel to x-axis) line solitons, but also by one line soliton and one curve soliton. Various types of multi-dromion solutions which are constituted by n straight line solitons parallel to the x axis and one curve soliton can be cast in a simple formula with two arbitrary functions. The KdV-type equation is not integrable because it cannot pass through the three nonparallel line soliton test.
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  Fusion Effect in Q₂ Evolution Equation

  Da-Li XUE, Guang-Lie LI

  理论物理通讯. 1996, 26(4): 491-494.

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  A momentum-conserved Q₂ evolution equation is obtained after the fusion process is included into the Altarelli-Parisi splitting-function argument.
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  An Analytical Study of the d-Dimensional q-State Potts Models on Lattice

  P. Y. ZHAO, J. M. NkJ

  理论物理通讯. 1996, 26(4): 495-498.

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  We investigate the phase structure of the d-dimensional q-state Potts models on lattice by the variational cumulant expansion (VCE) approach, we calculate the internal energy and specific heat for this model. Specially, we give the results for 2-dimensional q = 4,5,6 states Potts models. A comparison with Monte Carlo (MC) data is also presented. Our formalism can give the results for Potts models in any dimensionality d and any states q straightforwardly.