1989年, 第12卷, 第1期　
刊出日期：1989-07-30

  

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  Fractal Aggregation Near the Threshold

  YU Be-ming, YAO Kai-lun

  理论物理通讯. 1989, 12(1): 1-9.

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  In this papel, we present two fractal aggregation models, line pattern seed model (model 1) and point pattern seed model (model 2), which are particle-cluster models. Using the current models, we investigate the critical transition in fractal aggregation processes in two dimensions, and suggest a method for finding the critical transition point. The computer simulation results show that the critical concentration is P_ca=0.69±0.02 for model 1 and P_ca=0.72±0.01 for model 2, critical fractal dimension. D_c= 1.71±0.06 for model 1 and D_c=1.66±0.07 for model 2, which are in good agreement with those of DLA model (D=5/3) and experimental data. The results also show that the critical transition point in two dimensions seems to be inilependent of the size of lattices and the initial seed patterns. The results seem to belong to the same universality class.
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  Phase Transition of Ising Model on a Kind of Periodic Fractal Lattices

  Zi-dan WANG, Miao-yan SHI, Chang-de GONG

  理论物理通讯. 1989, 12(1): 11-16.

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  In this paper we introduced a periodic fractal structure (PFS) and studied the critical behavior of the nearest-neighbor-interacting Ising model within Migdal-Kadanoff bond-moving approximation. The critical curve equation and the formulas of the critical exponents were derived approximately in a special parameter region.
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  The Convection Instability of Bhnard-Rayleigh Fluid Under Varied External Force

  LUO Xue-li, WU Da-jin

  理论物理通讯. 1989, 12(1): 17-26.

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  A new model of Bknard-Rayleigh convection has been put forward from mantle convection and liquid crystal, where the external force deviates from constant to a lineal function of vertical dimension z. The dimensionless parameter ε is induced to describe the scale of this kind of deviations. Through linear stability analyses, we find that even-odd symmetry broken appears. By numerical calculation under rigid boundary conditions, we find that α_c is almost α constant but R_c decreases nonlinearly as ε increases, so the increase of ε benefits convection. When ε=0, all results reduce to the former works automatically.
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  On the Free Carrier-Negative U Center Interacting Model for the High-T_c Oxide Superconductor

  ZHANG Li-yuan

  理论物理通讯. 1989, 12(1): 27-32.

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  Using the free carrier-negative U center interacting model, we have investigated the superconducting transitionr,temperature T_c, the specific heat jump at T_c, the coherence length, the penetration depth, the thermodynamic critical field and the isotope effect for the high-T_c oxide superconductor. The theoretical values of these physical quantities are consistent with the experimental values. Further, the residual electronic specific heat in the superconducting state is explained as the result of the inherent instability in this superconductive mechanism.
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  Finite Temperature Self-Consistent Semiclassical Approach to the Incompressibility of Hot Nuclei

  LI Guo-qiang, XU Gong-ou

  理论物理通讯. 1989, 12(1): 33-45.

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  The self-consistent semiclassical approach is extended from zero temperature to finite temperatures. The nucleon densities of a hot nucleus at thermal equilibrium are determined. The centroids of isoscalar giant monopole resonances(GMR) are evaluated by making use of these densities with sum rules. The incompressibility of hot nuclei is studied with these centroids. It is found that the incompressibility decrepes as the temperature increases. A non-self-consistent finite temperature semiclassical approach with a Woods-Saxon mean field is also presented and compared with the self-consistent result.
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  Pair-Aligned Intrinsic States in Many-j Configurations

  SHEN Hong-qing, YANG Jian-jun

  理论物理通讯. 1989, 12(1): 47-55.

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  With the aid of a pair aligned model in many-j configurations and the Hamiltonian including monopole, quadrupole-pair forces and the quadrupole deformed field, the intrinsic states of deformed nuclei are determined by a variational method. The quadrupole moment is calculated and the effect of deformation on the intrinsic states is investigated. The results show that angular momentum (J=0,2,4) nucleon-pairs are dominant in the intrinsic states, so that, s, d, g bosons must be used in the study of deformed nuclei.
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  Analysis of N+¹⁹F(t+¹⁶O) Elastic Scattering with Three-Cluster QRGM and CGCT

  HOU Ren-chang, ZHAO Xuan, ZHU Zhi-yuan

  理论物理通讯. 1989, 12(1): 57-66.

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  The scattering of three-cluster system is studied with the quasi-resonating-group method (QRGM), which is an extended resonating-group method (RGM) by omitting the antisymmetrization of the nucleons in the double-magic cluster with other ones, and CGCT. As an example, the phase shifts and differential cross rrections of N+¹⁹F(t+¹⁶O) elastic scattering are evaluated. In the calculation an imaginary optical potential is introduced to take account of the effect of other reaction channels. The results show that the QRGM is a feaaible approximate method for many-nucleon system such as N+¹⁹F and can be used for other systems containing more nucleons.
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  Nucleon-Nucleon Rank Two Separable Potential

  LU Ding-hui, CHU Lian-yuan

  理论物理通讯. 1989, 12(1): 67-75.

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  A set of nucleon-nucleon rank-two separable potentials is constructed directly from the low energy twebody and three-body experimental data. The fitness of the physical quantities is suitable.
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  The Relativistic Many-Body Perturbation Treatment of the Long Range Part of the Nuclear Force

  CHENG Tan-sheng, YANG Xin-hua, ZHONG Yu-shu

  理论物理通讯. 1989, 12(1): 77-82.

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  Based on the many-body perturbation theory and cloudy bag model, the long range part of the nuclbar force is discussed. The results show that it agrees with one-pion exchange-potential in respect of both the radial dependence and the strength.
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  Fermions and the Autonomous λф⁴ Theory¹Fermions and the Autonomous λф⁴ Theory

  Sen-yue LOU, Guang-jiong NI

  理论物理通讯. 1989, 12(1): 83-94.

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  By means of Gaussian effective potential method, we investigate two models with coupling in 3+1 dimensions respectively. While the fermion effect through Yukawa coupling makes the autonomous λф⁴ theory more stable, it is shown that there are three different autonomous phases for model. The temperature dependences of these two models are similar to those in pure λф⁴ autonomous theory.
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  Nuclear Effect on the Nucleon Structure Functions and High P_T Jet Production in P-C Collisions

  HE Zhen-min, GAO Yong-hua

  理论物理通讯. 1989, 12(1): 95-98.

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  Using the empirical formula on F₂^N(C)/F₂^N(D) found by us and the analytical expression of the overall structure function d nucleon presented by CERNUA1 Collaboration, a simple calculating method on P+C→2jet+X process is presented. Our results will be checked by future experiments.
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  Phase Transition and Critical Behavior for XY Model on 2-Dimensional Random Triangle Lattice

  JIN Ke, CHEN Tian-lun, HUANG Wu-qun

  理论物理通讯. 1989, 12(1): 99-107.

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  The Monte Carlo renormalization group method is applied to discussing the nature of phase transition of XY model on 2-dimensional random triangle lattices. A line of fixed point and un-universal phase transition are found. The results are in agreement with Kosterlitz-Thouless theory. The susceptibility ehows a clear size-dependent behaviorin low temperature region. This means that it should be divergent in this region.
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  Two and Three Cocycles in a Hybrid Chiral Bag Model (A Comment on the Bosonization of Fermions)

  HOU Bo-yuan, WANG Pei

  理论物理通讯. 1989, 12(1): 109-116.

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  In this paper, a 3-cocycle is realized in a hybrid chiral bag model as quantities at the boundary of the bag. The equivalence between charges of gauged boson currents in Skyrme model and full gauge transformation generators is established both in 3+1 dimensions and 1+1 dimensions.
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  The Thermodynamic Properties of Superconducting State in BZA Mean-Field Theory

  SU Gang

  理论物理通讯. 1989, 12(1): 117-120.

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  The thermodynamic properties of superconducting state in BZA mean-field theory of RVB superconducting mechanism are evaluated in this letter.
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  Darboux Transformation Method for Finding Soliton Solutions of the Landau-Lifschitz Equation of a Classical Heisenberg Spin Chain

  Nian-Ning HUANG, Bing XU

  理论物理通讯. 1989, 12(1): 121-126.

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  Darboux transformation method is used to find soliton solutions of the Landau Lifschite equation of a classical Heisenberg spin chain.