1998年, 第30卷, 第2期　
刊出日期：1998-09-15

  

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  Quantum Statistical Properties of Photons and Atoms in Interaction of an Atomic Bose-Einstein Condensate with Lasers

  KUANG Leman

  理论物理通讯. 1998, 30(2): 161-168.

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  In this paper, we study quantum statistical properties of atoms and photons in interaction of ⁷Li-atornic Bose-Einstein condensate in the ground-state hyperfine sublevels with laser fields. We investigate not only quantum conversions between atoms in the condensate and photons in the quantized laser field, but also transfer of nonclassical cha acteristics of atoms and photons between input states and output states when the atom field is initially in a number state and the quantized laser field is in the even coherent state and the odd coherent state, respectively. We find various conditions to realize these quantum conversions. We also study atom-photon quantum correlations and their input-output conversions. It is indicated that there are atom-field nonclassical correlations.
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  Exact Solution of Jaynes-Cummings Model Without Rotating Wave Approximation

  FENG Mang, WANG Kelin, SHI Lei, FANG Ximing, YAN Min, ZHU Xiwen

  理论物理通讯. 1998, 30(2): 169-172.

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  In coherent-state representation, the Jaynes-Cummings (JC) model in the absence of rotating wave approximation (RWA), i.e., in detuning case, is treated by the solution of some differential equations with constant coefficients and can be exactly solved. This approach can be easily extended to deal with the JC model without RWA in more complicated cases.
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  Influences of the Aharonov-Bohm Flux on the Improved Soliton in a One-Dimensional Ferromagnetic Ring

  CHEN Hao, CHEN Yuan

  理论物理通讯. 1998, 30(2): 173-176.

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  Influences of the Aharonov-Bohm flux on the improved soliton in a one-dimensional ferromagnetic ring are considered. The results show that the width, the peak, the rest energy and the effective mass of the improved soliton are dependent upon the Aharonov-Bohm flux and influences of the Aharonov-Bohm flux on the improved soliton are greater than those on the usual soliton.
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  Effect of a Very Strong Confinement on the Structures of Low-Lying States of a Three-Electron Quantum Dot

  LI Xungui, WU Hong, BAO Chengguang

  理论物理通讯. 1998, 30(2): 177-186.

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  Features of the low-lying states of a three-electron quantum dot under a very strong confinement are investigated by few-body methods. We find that the energy spectra are changed greatly compared with the energy spectra under a weak confinement; and the mechanism producing the magic numbers remains working just as in the case of a weak confinement. Furthermore, the degeneracy law of the energy spectra of the low-lying states and the platform effect of the degeneracy degree in close connection with the uncontinuous change of some macroscopic physical properties of materials are discovered for the first time.
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  Using Meso-Targets to Achieve Targeting

  QIN Tuanfa, NI Wansun, DENG Hao, CHEN Guangzhi

  理论物理通讯. 1998, 30(2): 187-192.

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  In this paper a method is developed which directs trajectories to a target by using meso-targets. The method can rapidly direct orbits from an arbitrary initial state to a target by making small perturbation of available system parameters. It is simple, efficient and reliable. Numerical experiments are given in Hhnon map.
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  Instantaneously Dynamical Response and Correlation Functions in Independent-Oscillator Model

  GU Jianzhong, WU Xizhen, ZHUO Yizhong, ZHAO Enguang

  理论物理通讯. 1998, 30(2): 193-198.

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  For the independent-oscillator model (IOM), the explicit expressions of the instantaneously dynamical response functions (Χ₁ + Υ,t₁), X(t₁ + Υ,t₁)) and correlation functions (φ(t₁ + Υ,t₁)+Φ(t₁ + Υ,t₁)) for both the system and environment are derived. It is shown that for external perturbation the environment of IOM is dynamically stable and the system is oscillatory. Although the external perturbation exists, there is still strongly temporal correlation for the system, for the environment, however, the temporal correlation quickly decays with the second time variable Υ and is almost independent of the first time variable t₁, nevertheless is significantly affected by dissipation. It is shown that the environment behaves as a heat bath from the dynamical point of view.
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  The Relation Between the Two Methods for Describing Markovian Noises

  YANG Ming, CAO Li, WU Dajin, LI Zaiguang

  理论物理通讯. 1998, 30(2): 199-204.

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  A general method used to calculate the time-dependent probability distribution from the switching time distribution ψ(t, a) and the transition probability ρ(a, b) for Markovian noises is presented, and the way how to describe the noises treated as diffusion processes such as O-U noise by the jump model (namely, ψ(t, a) and ρ(a, b)) is given, which makes it possible to apply the stochastic trajectory technique and the definition method to the above noises.
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  Probability and Joint Probability Distributions for Systems Driven by Correlated Colored Noises

  ZHU Youxin, LI Xiangling

  理论物理通讯. 1998, 30(2): 205-212.

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  This paper deals with systems driven by correlated colored noises. The evolution equations for both the single and joint probability distribution functions are derived. It is shown that both the stationary and dynamical properties of the systems are affected by correlated colored noises. These results are obtained by means of the systematic use of the ordered cumulant-expansion technique.
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  A Unified Description of N-N and Y-N Interactions on Quark Model

  ZHANG Zongye, YU Youwen, SREN Pengnian, DAI Lianrong

  理论物理通讯. 1998, 30(2): 213-218.

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  A quark-quark interaction is derived from the linear expression of Lagrangian which is invariant under the SU(3)_L × SU(3)_R infinitesimal transformation, and further used to make a unified study on the N-N and Y-N scattering processes.
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  Nuclear Liquid-Gas Phase Transition Shown in Multifragment ation

  ZHENG Yuming, SA Benhao, WANG Hui

  理论物理通讯. 1998, 30(2): 219-224.

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  The Incomplete-Fusion-nagmentation Model has been used to reproduce nicely the experimental evidence of liquid-gas phase transition probed in the reaction of Au + Au at 600A MeV. The analysis of the relative yields of decay modes for the projectile remnant as a function of bound> shows clearly the competition and transformation processes of various decay modes of projectile remnant with decreasing of bound>. The agreement between theoretical and experimental results for the anaJysis of relative yield of decay modes indicates that the experimental evidence of liquid-gas phase transition is composed of the decay mode transformations.
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  Fractional Parentage Coefficients for Composite Pairs

  LU Dahai, YANG Liming

  理论物理通讯. 1998, 30(2): 225-228.

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  A new set of fractional parentage coefficients is introduced to build the orthogonal basis of states with many S and D pairs in the microscopic theory of low-lying collektive motion in nuclei.
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  Double Diffractive Dissociation Process p + p(p) → X_p + X_p(p) + Π⁺ + Π^- at High Energy and the Pomeron Model of Donnachie-Landshoff

  PENG Hong'an, WANG Wenyong, JU Changsheng, HE Zhenmin

  理论物理通讯. 1998, 30(2): 229-236.

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  Large p_γ charged pion pair produced in Double Diffractive Dissocjation (DDD) process at high energy is studied with double pomeron (IP) exchange mechanism. Using DonnachieLandshoff pomeron model we have calculated the cross-section of the process at the energy interval from ISR to LHC when the rapidity of the charged pions is approximately equal to zero. It is shown that this process is the favorite in experiments which could effectively be used to examine Donnachie-Landshoff pomeron model and provide a possibility to check the value of the suppression coefficient N².
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  Spontaneous Symmetry Breaking and Vacuum of Charged Relativistic Boson Condensate

  ZHANG Yang

  理论物理通讯. 1998, 30(2): 237-244.

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  We study Bose-Einstein condensation of a charged relativistic boson system as a phenomenon of spontaneous symmetry breaking. By using the Bogoliubov's quasi-average method, it is found that the vacuum expectation values of the scalar fields are nonvanishing, indicating the nonperturbative nature of the condensation. The vacuum of the condensate is explicitly constructed, which is a superposition of states with different charges. A relation is found between the vacuum and the Stagerstam's coherent states of definite charge.
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  The Strong Interaction in Chromodynamics Ⅲ

  HU Ning

  理论物理通讯. 1998, 30(2): 245-248.

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  The exact solution of the relativistic wave equation for the quark and antiquark in meson states using the soliton potential of the gluon field as the interaction potential is obtained. It is found that the motion of the quark and antiquark inside meson states is essentially simple harmonic oscillation. The mass spectra of all known mesons and baryons and the split of mass levels of J/Ψ and η_c particles and of Ψ(3685) and Ψ(3770) particles obtained in Refs [1] and [2] from this equation agree very well with the experiment. The rest masses of ordinary and charm quarks estimated by this wave equation are much smaller than those of the ground states. This indicates that the motion of all kinds of quarks inside the hadrons is relativistic.
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  Nonlocal Electrodynamics in 2+1 Dimensions from Chern-Simons Theory

  LIN Qionggui

  理论物理通讯. 1998, 30(2): 249-256.

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  The theory of a spinor field interacting with a pure Chern-Sirnons gauge field in 2+1 dimensions is quantized. Dynamical and nondynamical variables are separated in a gaugeindependent way. After the nondynamical variables are dropped, this theory reduces to a pure spinor field theory with nonlocal interaction. Several two-body scattering processes are studied and the crbss sections are obtained in explicitly Lorentz-invariant forms.
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  The Reduction of Differential Calculus on Direct Product Group

  FENG Bo, LI Jianming, SONG Xingchang

  理论物理通讯. 1998, 30(2): 257-262.

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  In this paper, we give a reduction of universal differential calculus on a direct product group P by two different methods. We prove the consistency of reduction and give some examples of the application to particle physics model.
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  The su_µ(1,1) Coherent States on the Quantum Complex Plane

  GONG Renshan

  理论物理通讯. 1998, 30(2): 263-268.

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  The su_µ(1,1) coherent states on the quantum complex plane are introduced. It is shown that the Bargmann representation corresponding to these coherent states may be constructed with analytic functions of quantum complex variables. By means of the integral and differential calculus on the quantum complex plane some properties of the Bargmann representation are discussed.
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  The Radial-Azimut ha1 Inst ability of an Isothermal Magnetized Accretion Disk

  YANG Lantian, WU Shaoping, LU Ye, WU Xuebing

  理论物理通讯. 1998, 30(2): 269-274.

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  The radial-azimuthal instability of an isothermal magnetized accretion disk is examined in this paper. We find that the azimuthal perturbation enhances the instability of the magneto-acoustic and non-axisymmetric modes. The magnetic field induces and enhances the instability of magneto-acoustic modes, but stabilizes the non-axisymmetric modes in the outer disk. The viscous modes are always stable. The instability of magneto-acoustic modes are dominant in this disk.
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  Cosmological Constraint Revisited from K Band Galactic Counts

  XU Wen, YU Yunqiang, ZHOU Guorong

  理论物理通讯. 1998, 30(2): 275-280.

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  The information of Ω_Λ of a flat universe is extracted from K band galaxy number counts, without using evolution (NE) models. Cowie et al.'s observations, with model input luminosity functions taken from Efstathiou et al. (1988), Loveday et al. (1992) and Mobasher et al. (1993), give (Ω_Λ) in the range: 0.59～0.81 plus a typical random error of σ_ΩΛ = 0.2 -0.1, respectively. Keck's observations give Ω_Λ = 0.9. We conclude that either the normalization of nearby luminosity function is too high or the cosmological constant cannot be too large.
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  Nonlinear Oscillations in One-Zone Stellar Model

  CHEN Fusheng, JIANG Shiyang, CHEN Yan

  理论物理通讯. 1998, 30(2): 281-286.

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  If one-zone models are available for some pulsating stars and the motion remains close to adiabaticity, the oscillation and stability criterion of the star have been analyzed by canonical perturbation theory and optimal control theory, separately under different function values b on the right-hand side of E_q. (10). We found that (ⅰ) If the introduction of a given perturbation function of time b(t) is substituted into the right-hand side of E_q. (10), and energy-optimal control of a nonlinear oscillator is satisfied, the oscillation in one-zone model is unstable. (ⅱ) If b is subject to the constraint |b| ≤ 1, and time-optimal control is satisfied, the oscillation in one-zone stellar model is stable. (ⅲ) The periodic oscillation criterion is obtained by a simple method, if b is regarded as a constant of integration in E_q. (10). It shows that the adiabatic exponent Γ₁ is all important. When Γ₁ is greater than or equal to 4/3, the periodic oscillation should occur in one-zone stellar model; when Γ₁ is less than 4/3, and under the additional condition of |B| < B_c, the periodic oscillation could not occur in this model.
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  Gamma-Ray Pulsars

  SHI Tianyi, LI Guang

  理论物理通讯. 1998, 30(2): 287-292.

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  Based on Arons and Scharlemann model, the mechanism of γ-ray emission of pulsars is discussed. The criterion for radio pulsars appearing also as γ-ray pulsars is presented, after considering both dipole and quadrupole magnetic fields. The luminosities and fluxes of six known γ-ray pulsars are calculated. Using the criterion, twenty four possible candidates for γ-ray pulsars are listed and some characteristic quantities of them are also given.
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  General Solutions of Geometric Phase of Neutron in Rotating Magnetic Fields

  CHEN Xiaoyu

  理论物理通讯. 1998, 30(2): 293-296.

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  The exact solutions of the closed evolution of spin states in rotating magnetic fields are described for the most general cases via eigenstate method. A simple algorithm for calculating the geometric phase is exploited.
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  Quantum Mechanical Effects in a Non-Dissipation Mesoscopic Coupled Circuit in the Presence of Source

  W Guo'an, YU zhaoxian, LIU Yehou

  理论物理通讯. 1998, 30(2): 297-300.

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  Under the squeezed vacuum state, the quantum zero point fluctuations for both the charge and current of a non-dissipation mesoscopic coupled circuit in the presence of source are given. The quantum mechanical effects of this circuit at zero temperature are studied.
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  Squeezing Dynamics for an Electron in a Uniform Magnetic Field Studied in a Convenient Representation

  FAN Hongyi, FAN Yue

  理论物理通讯. 1998, 30(2): 301-304.

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  We study squeezing dynamics for an electron in a uniform magnetic field in a convenient representation proposed in Ref.[1]. The theoretical basis of the squeezing mechanism through a change of the magnetic field intensity is examined. Some physical effects caused by the squeezing are discussed. The normally ordered squeezing operator corresponding to the varying magnetic field can be derived by virtue of the technique of integration within an ordered product of operators.
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  A New Type of Shape-Invariant Potential

  JIA Chunsheng, WANG Xiaoguo, YANG Qiubo, HE Su, LI Hao

  理论物理通讯. 1998, 30(2): 305-308.

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  It has been shown that Hulthen potental and isotonic harmonic oscillator potential are shape-invariant potentials with a translation of parameters, and isotonic harmonic oscillator potential and three-dimensional harmonic oscillator potential belong to a type of shape-invariant potentials.
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  Exact Solutions of Nonlinear Wave Equations

  FAN Engui, ZHANG Hongqing

  理论物理通讯. 1998, 30(2): 309-312.

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  Darboux transformations and a fourth-order ordinary equation which can be transformed into a Bernoulli equation are used for investigation of several classes of exact solutions for well-known Kadomtsev-Petviashvili (KP) equation, KdV equation and Hirota-Satsuma (HS) equation, solitary wave solution and wave solution are among them.
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  The Dependence of the Pion Dispersion Relation on the Short-Range Correlation

  LIU Lianggang, CHEN Wei, MEI Zhonghau, LUO Xiangqian

  理论物理通讯. 1998, 30(2): 313-316.

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  The relativistic Δh excitation polarization insertion of pion propagator is given and its real part is compared with the nonrelativistic ones, its imaginary part and the pion dispersion relation are studied by two sets of short-range correlation Landau-Migdal parameter g'. We find that the imaginary part has large difference for some energies and momenta, the pion dispersion relation shows small difference. The short-range correlation suppresses both the ph and Δh excitations. The pion dispersion relation at normal nuclear density shows no evidence for pion condensation. The Δh polarization insertion and the pion dispersion relation are dependent on the nuclear density and the effective mass of nucleon and Δ-isobars strongly.
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  A Note on Soldering Chiralities

  MIA0 Yangang, CHEN Chuanhong

  理论物理通讯. 1998, 30(2): 317-320.

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  Soldering chiralities is studied in the linear formulation of chiral bosons. It is discovered that a counterterm, which seems to describe an antichiral boson but in fact a scalar boson, has the function to cancel the chirality of a chiral boson. As a result, the total Lagrangian describes a scalar field.