1990年, 第13卷, 第1期　
刊出日期：1990-01-30

  

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  A Monte Carlo Study of Carrier Distribution in Yba₂Cu₃O₇

  Shi-jie XIONG, W.Y. LIANG

  理论物理通讯. 1990, 13(1): 1-10.

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  A Monte Carlo simulation has been carried out on the carrier distribution in the Ba-O plane of Yba₂Cu₃O₇, where the O-2p_z orbitals perpendicular to the plane are strongly hybridized with 3d_z² orbitals in adjacent Cu planes, while the in-plane O-2p_z and O-2p_y orbitals, which are nonbonding with respect to the Cu-3d orbitals, form two nearly degenerate subbands. The degeneracy is removed by the distortion of the lattice. A tight-binding Hamiltonian is constructed for such a coupled electronlattice system and the Monte Carlo simulation is made for a sample containing 35×35 unit cells with periodic boundary condition at various temperatures. Although the total number of carriers is fixed, the results show approximately a linear temperature dependence of in-plane hole density, and this is in good agreement with the Hall effect measurements. The distortion of the lattice is found to exhibit random character with some short range order. The relations to the other transport properties and to other superconducting oxides, especially the Nd-Ce-Cu-O systems, are also discussed.
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  Electronic Spectroscopies of the Mixed Valence Ce Compounds: A Slave Boson Approach to the Impurity Model

  Tsung-han LIN

  理论物理通讯. 1990, 13(1): 11-18.

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  A slave boson approach to the electronic spectroscopies for the mixed valence Cecompounds in the impurity model is presented. Three valence configurations of Ceion (f⁰, f¹ and f²) are considered so the framework of the theorv can be used for culculating both XPS and BIS. The spectrum under mean field approximation is presented.
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  On the Liguid-Gas Phase Transition and the Instability of Hot Nuclei

  LI Guo-qiang

  理论物理通讯. 1990, 13(1): 19-32.

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  Based on a simple semi-empirical energy density, the free energy density for a hot nucleon system is derived, from which the equations of state P(T, p) and chemical potentials μ_q(T, p) for both finite nucleus and infinite nuclear matter are acquired. The liquid-gas phase transition and the instability of hot nuclei are analysed with these ingredients within the framework of thermodynamic's. Both critical temperature T_c for infinite nuclear matter and limiting temperature T_lim, for finite nuclei are predicted and compared with previous calculations.
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  The Estimation of Nuclear Fusion Rate in Crystal

  CHU Lian-yuan, LU Ding-hui

  理论物理通讯. 1990, 13(1): 33-40.

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  A fusion reaction rate of deuteron in the crystal of palladium deuteride is theoretically estimated at about 10^-55/s.This result is very amall. The fusion rate in the other deuterides such as titanium deuteride and zirconium deuteride would not be large too. Therefore it is impossible to use the cold nuclear fusion in such crystals for the source of energy.
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  The Fibre Bundle Formulation of σ-Model and SUSY σ-Model

  Bo-yu HOU, Pei WANG, Bo-yuan HOU, Li-ning ZHANG

  理论物理通讯. 1990, 13(1): 41-48.

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  In this paper, we present an analysis of the general symmetry properties of some physical systems, where especially the method of h_μ(x), k_μ(x) decomposition of connection is used. Then we reformulate the σ-model and the SUSY σ-model in the framework of fibre bundle theory. By comparisons, we obtain the SUSY partner of "linearized" equation or Lax pair of σ-model.
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  The Holomorphic Quadratic Differentials of Amplitudes for Strings with Boundaries

  Zhe CHANG

  理论物理通讯. 1990, 13(1): 49-56.

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  We show that the amplitudes for strings with boundaries can be written as complex structure forms. The C, curves used by Krichever and Novikov to parametrize compact Riemann surfaces satisfy the string boundary conditions. Thus they can be regarded as the initial and final states of the atrings. Using Krichever-Novikov bases, we explicitly construct a basis of holomorphic quadratic differentials for strings with boundaries.
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  Constraints on Masses of Composite Particles Containing Exotic Quarks

  Bang-rong ZHOU

  理论物理通讯. 1990, 13(1): 57-62.

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  It is shown based on some rigorously proven mass inequalities that some of the composite particles containing the SU_c(3) 6-plet and 8-plet quarks (q₆ and q₈) could appear in TeV physics if q₆ and q₈ exist in nature and can be used in the scheme of dynamical symmetry breaking of the electroweak gauge group.
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  Physical Effects of U(1)-Induced Gauge Field and Their Non-Adiabatic Corrections for the Cases with Arbitrary Spin

  Chang-pu SUN, Mo-lin GE, Qing XIAO

  理论物理通讯. 1990, 13(1): 63-70.

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  By making use of the improved Born-Oppenheimer approximate method, we deal with the separation of spin variable and space variable of neutral particle with arbitrary spin in inhomogeneous magnetic field and non-adiabatic corrections for the problems are thereby computed as perturbations. We also analysis the geometrical properties of loop phase of the induced gauge potential and point out its observable effects relating to Bitter and Dubbers'experiment. Finally, we discuss the transitions between the instantaneous spin states as non-adiabatic effects resulting from inhomogeneity of the magnetic field.
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  The Embedding of Quantum Algebra U(gl(n+1)) in Irreducible Representations of U(gl(n+1))

  Bo-yu HOU, Kang-jie SHI, Xing-chang SONG, Pei WANG

  理论物理通讯. 1990, 13(1): 71-78.

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  Using a formula derived by Jimbo, we express the generators of U(gl(n+1)), the q-analogue of U(gl(n+1)) in an irreducible representation with Gel'fand basis, as functions of the generators of U(gl(n+1)).
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  A Model with Spontaneous Symmetry Breaking and Its Kink Soliton Solution

  Sen-yue LOU, Guo-xiang HUANG, Guang-jiong NI

  理论物理通讯. 1990, 13(1): 79-84.

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  A model with spontaneous symmetry breaking is presented. The exact kink which is stable and kink lattice solutions are obtained. When the parameter of the model λ tends to zero, all the results reduce to those of the well-known Φ⁴ model.
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  A Consideration of BRST Cohomology in the First Quantization of RNS String

  Hong-liang HU, Rong WANG, Yue YU

  理论物理通讯. 1990, 13(1): 85-90.

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  The difference of Grassmanian even-odd and degree even-odd of (super-) conformal ghosts is stressed. With some modifications in the BRST charges and the commutation relations, it can be shown that the first quantization of RNS strings allows the BRST cohomology analysis.
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  A Phenomenological Approach to the Ω^- Rradiative Decay

  Xue-qian LI, Qin-rou WEN, Li LIAO

  理论物理通讯. 1990, 13(1): 91-98.

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  Even though a lot of.effort has been made, the ΔS = 1 radiative hyperon decays still remain mysterious. Kamal and Verma improved Gilman and Wise's model which suggested a phenomenological way to fit the data for both Σ⁺→pγ and Σ^-→Σ^-γ. However, this model contradicts M.K. Gaillard's theorem. Now we propose a modified phonomenological model and, 1). check M.K. Gaillard's theorem in terms of the data; 2). give a prediction to the Ω^- radiative decay which will be tested in the future experiments.
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  Two Pairs of Kink-Antikink Solutions for the Off-Double-Well Potential System

  WANG Wen-guo

  理论物理通讯. 1990, 13(1): 99-102.

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  A single atomic chain with off-double-well potential is considered. The dynamical equation is solved and two pairs of kink-antikink solutions are obtained. Our result may be used to explain the protonic conductivity in some.hydrogen-bonded substances.
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  Model Equations and Their Solitary Wave Solutions in Cylindrical Coordinate System

  HUANG Guo-xiang, LOU Sen-yue, DAI Xian-xi

  理论物理通讯. 1990, 13(1): 103-107.

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  The method of multiple-scales is used to investigate the evolution of a weak nonlinear internal waves between two-layer fluids in cylindrical coordinate system. Two reduced model wave equations, which we call a modified cylindrical KdV equation for axially symmetric case and a modified cylindrical KP equation for non-axially symmetric case, are derived and their solitary wave solutions are also obtained by relating them i to the modified KdV equation by means of an appropriate variable transformation.
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  Scale Invariance and Minimum Extension of the SU(2)×U(1) Model

  M.D. XIN,

  理论物理通讯. 1990, 13(1): 109-112.

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  In this note, we discuss a minimum extension of the SU(2)×U(1) model to include both gauge invariance and scale invariance by introducing a complex phase transformation and related complex gauge field, in which the imaginary part corresponds to the Weyl's vector field.
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  A Possible Generalization of Jaynes-Cummings Model with Degenerate Spectrum

  WU Qiang, FAN Hong-yi

  理论物理通讯. 1990, 13(1): 113-118.

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  We propose a generalized Jaynes-Cummings model (JCM) for three two-level atoms and three-mode radiation field with the interaction being H₁=λ(a₁⁺a₂⁺σ_1-σ_2-+a₂⁺a₃⁺σ_2-σ_3-+a₁⁺a₃⁺σ_1-σ_3-+H.C.). This model is characteristic of possessing partly degenerate spectrum. Some transition process of this system is calculated.
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  Mass Splitting Formulae for Skyrmions with Strangeness in the Sub-SU(3) Skyrme Model

  Guo-wei WU, Mu-lin YAN

  理论物理通讯. 1990, 13(1): 119-124.

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  Some new mass splitting formulae for octet-and decuplet-baryons are obtained in the Sub-SU(3) Skyrme model in SU(4) by a feasible perturbative treatment (GMC method). The results show that the flavor symmetry for usual baryon octet and decuplet is an SU(3) subgroup in SU(N) with N>3 rather than a pure SU(3).
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  A Discussion About Cosmic Microwave Background Excess

  HUANG Wu-liang

  理论物理通讯. 1990, 13(1): 125-128.

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  For cosmic microwave background excess, it could be explained by a process during H recombination period from z_i to z_e (z_i/z_e～50), if for H-He mixture weak plasma, there may exist a substeady level (population inversion). The main feature of this model lies in a decrease at the Rayleigh-Jeans part of CMB near y～0.5.
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  Dark Matter, Supercluster Complex and Large Scale Stream

  HUANG Wu-liang

  理论物理通讯. 1990, 13(1): 129-132.

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  For supercluster complex and large scale stream of the universe, both of them could be explained in an HDM dominated model, which also gives an explanation about why in larger invisible structiire it can previously be formed to be the smaller visible structure, if the mass of HDM particle m_d～0.3 eV and the universe is exactly flat (Ω=1).
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  Theory of Internal Fraction in the High T_c Superconductor YBa₂Cu₃O_7-δ

  Du-ping YUAN, Chien-hua TSAI

  理论物理通讯. 1990, 13(1): 133-133.

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  The internal fraction in the high T_c superconductor YBa₂Cu₃O_7-δ arising from diffusion of oxygen atoms between the O(1) and O(5) sites under thz influence of a periodic mechanical strain is studied mkroscopically in the linear approximation of relaxation process. It is analysed for various specific cases both in the tetragonal and the orthorhombic phases as well as in the case of polycrystalline samples.
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  A Renormalization Analysis of One-Dimensional Thue-Morse Lattice

  Ming-guang QIN, Hong-ru MA, Chien-hua TSAI

  理论物理通讯. 1990, 13(1): 133-133.

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  The one-dimensional Thue-Morse sequence with a generating matrix of determinant zero has been suggested to be intermediate between a periodic structure and a standard quasiperiodic structure like the Fibonacci sequence. The renormalization procedure developed in our previous study of one-dimensional Fibonacci quasicrystal is here applied to discuss the electronic spectrum of a tight-binding Thue-Morse quasicrystal. The resulting integrated electronic density of states shows indeed, a structure which is more like that of a periodic chain than a Fibonacci quasicrystal. We suggest the analytical procedure can be extended to study one-dimensional quasicrystals of any other kind, the two-dimensional Penrose lattice as well as three-dimensional real quasicrystals.
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  Quantum Interference Effect in General Rotating Systems

  Hong-hua XU, Chien-hua TSAI

  理论物理通讯. 1990, 13(1): 134-134.

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  As the mechanical counterpart of the Aharonov-Bohm effect and the Aharonov-Cashier effect in a magnetic field, the existence and possibility of observation of a quantum interference effect between the split paths of a coherent particle beam in a uniformly rotating frame have been studied previously. The discussion is now generalized to the case of a reference frame rotating at arbitrary time varying angular velocity about a fixed center. The phase difference between the split beams of particles and the resulting interference pattern depend not only upon the speed, but also upon the orientation of the axis of rotation. The conclusion may have, therefore, inferences on gyroscopic applications.
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  On the Perturbation Expansion of Closed Time Path Green's Functions

  Hong-hua XU, Chien-hua TSAI

  理论物理通讯. 1990, 13(1): 134-134.

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  The incoming interaction picture is introduced in accordance with the adiabatic hypothesis. A generalized Wick's theorem and, accordingly, a real time formalism of perturbation theory at finite temperatures are constructed for the closed Time Path Green's Functions (CTPGF). This new approach is illustrated in terms of the simple case of an electron-phonon system.