1999年, 第31卷, 第1期　
刊出日期：1999-01-30

  

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  The Energy of Six-Quark Cluster System

  YU Youwen, ZHANG Zongye, YUAN Xiuqing

  理论物理通讯. 1999, 31(1): 1-4.

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  The energies of the (OS)⁶ six-quark cluster states are calculated in the chiral SU(3)quark model. The results show that some states with higher strange number have more attractionfrom the chird SU(3) coupling, and this feature is interesting in discussing if thereexists some narrow width six-quark states with high strangeness.
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  GCP Code and Analysis of J/ψ Suppression in p-A and A-A Collisions

  YAO Xiaoxia, CHAO Weiqin, PANG Yang

  理论物理通讯. 1999, 31(1): 5-12.

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  Using the General Cascade Program (GCP), the production and absorption of J/ψ,in p-A and A-A collisions have been studied. Nucleon absorption mechanism and comoverabsorption mechanism are considered to investigate the J/ψ suppression. The results agreewell with experimental data of J/ψ production, escept for the data in Pb-Pb collision.
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  Gravitational Effects in the Propagation and in the Emission of Light

  PENG Huanwu

  理论物理通讯. 1999, 31(1): 13-20.

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  Following Chou's viewpoint that the Cartesian system of space coordinates and timedefines a Minkowskian space-time in which Einstein's field equations and the harmonic conditionare the laws of gravitation (Ref.[1]), we study the effects of an external gravitational fieldin the propagation and in the emission of light respectively from the generalized Maxrwell andDirac equations of the general theory of relativity by geometric optics and quantum mechanics,and get the usual results for the red shift. For the naively homogeneous and isotropic model ofcosmology (the case with k = 0 in the Robertson-Walker scheme) closed form for the relationbetween distance and red shift is obtained, which indicates that a new way of analyzing theobservational data with not too small red shifts is needed.
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  Dilatation Transformation on Curvilinear Reaction Path

  ZHAO Meishan

  理论物理通讯. 1999, 31(1): 21-26.

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  We present a dilatation transformation anlysis on curvilinear reaction path, andanalyze the curvature effect of complex scaling on the prediction of molecular reaction thresholdresonance. An example of numerical calculation was carried out for the prediction of thresholdresonance of H + H₂ molecular scattering with and without consideration of the reactionpath curvature. We found, in the studied system, that the curvature provides a correction tothreshold resonance lifetime as large as 25%.
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  A One-Dimensional Model of Hydrogen Molecular Ion

  DUAN Yiwu, YIN Menya, AN Weike, HE Chunshan

  理论物理通讯. 1999, 31(1): 27-32.

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  We present a study on a one-dimensional hydrogen molecular ion under the Born-Oppenheimer approximation. A canonical transformation produces the classical system directlyto be a pendulum. The quantum Schrodinger equation is solved analytically and theelectronic energy curves show that the bound states of this 1D model differ from the 2D and 3DH₂⁺. The vibration spectroscopy is also obtained by employing the Morse's eigen wavefunctionsas basis vectors to diagonalize the Hamiltonian for R. The semiclassical quantization yieldselectronic energies in agreement with the quantum ones reasonably.
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  Dynamics of the Driven Jaynes-Cummings Model

  FU Liping, ZHENG Shibiao, GUO Guangcan

  理论物理通讯. 1999, 31(1): 33-38.

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  We study the dynamical features of the Jaynes-Cummings model with the atomdriven by an external classical field in the case that the cavity field is initially in a Fock state.We find the dynamical variables by using dressed states in the bare atom representation. Weshow that the dynamical behavior of the cavity field can be strongly modified by the externalclassical field. We also find that the cavity field is super-Poissonian after some interaction timeif the external field is strong enough.
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  Energy Spectrum and g Factors of α-A1₂O₃:Ni²⁺ and Their Pressure-Induced Shifts

  MA Dongping, MA Xiaodong, CHEN Jurong, LIU Yanyun

  理论物理通讯. 1999, 31(1): 39-48.

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  A unified calculation of the whole energy spectrum and g factors of the ground stateat normal pressure and their pressure-induced shifts for α-A1₂O₃:Ni²⁺ has been carried outon the basis of the theory of pressure-induced shifts and the diagonalization of the completed⁸ energy matrix adopting C_3υ symmetry. The calculated results are in very good agreementwith all the experimental data. The rates of change of all the levels with respect to variousparameters and the contributions to typical levels or splittings from various parameters havebeen calculated. The distinct differences of pressure-induced shifts of various levels are immediatelydetermined by their characteristic dependencies on -the parameters of interactions,and the pressure-induced shifts (especially those of t₂⁶e^{2 1}EÊ) have provided important or,crucial criteria for the correctness of the calculation and assignment of the energy spectrum of α-A1₂O₃:Ni²⁺.
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  Effect of Pressure on Heavy-Fermion Metals

  LIN Hai, LI Zhengzhong, XIAO Mingwen, XU Xiaohua

  理论物理通讯. 1999, 31(1): 49-56.

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  In this paper, we introduce a microscopic theory for the heavy-fermion metals under applied pressure in the framework of the slave-boson mean-field approximation of the U = ∞ Anderson lattice model. The density of states for ƒ electrons and its variation with the pressure are calculated self-consistently The pressure-dependencies of the low-temperature specific-heat coefficient, magnetic susceptibility, and the resistivity in the electron-type and hole-type heavy-fermion metals are obtained. The results provide a unified explanation on the two opposite pressure-dependent effects observed in Ce-based and Yb-based compounds.
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  Green's Function Theory of Linear Magnetic Chains with Anisotropic Coupling

  SONG Yun, FENG Shiping, MA Benkun

  理论物理通讯. 1999, 31(1): 57-64.

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  The one-dimensional spin-1/2 ferromagnetic and antiferromagnetic chains with anisotropic coupling are studied within the Green's function theory in both planar and uniaxial regimes. The spin Green's functions are decoupled at a stage one-step further than the Tyablikov's decoupling under the constraint ²>= 0. The behaviors of the correlation functions are studied in the entire temperature regime. The thermodynamic properties are also discussed, and the result is consistent with the numerical simulation.
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  Electronic Structure of Quasi-One Dimensional Models

  WANG Huaiyu

  理论物理通讯. 1999, 31(1): 65-72.

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  Ladder models are studied as quasi-one dimensional tight binding systems. A set ofiteration formula is derived for calculating local densities ofstates for various ladders includingperiodic, quasiperiodic and disordered ones. Band structures are analyzed.
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  Modeling of Influence of Helix Geometry on the Constitutive Parameters of the Chiral Medium

  XIANG Linchuan, LIU Zuli, YAO Kailun

  理论物理通讯. 1999, 31(1): 73-78.

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  Computations are made to estimate the influence of geometry of the helixes in an artificial chiral medium made by embedding small conducting helives in a lossy isotropic host material on the three constitutive parameters of the medium, by using a proposed model which explicitly includes the first-order effects of reradiation from the helixes, near-field loses and mutual coupling between helixes.
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  A New Principle to Determine the Variational Parameter for the Variational-Cumulant Expansion

  WANG Qing, CHEN Tianlun

  理论物理通讯. 1999, 31(1): 79-84.

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  The key point of the variational-cumulant expanhon is the determination of the variational parameter. In this paper, we present the improved mean-field hypothesis (IMFH) which is the bdse to determine the parameter. The new method derived from the IMFH shows advantage over previous methods. The critical temperature and some thermal dynamical functions for the Heisenberg model are calculated with the new method.
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  Self-Organization and Phase Transition in Two-Dimensional Traffic-Flow Model

  SHI Yu

  理论物理通讯. 1999, 31(1): 85-90.

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  An analytical investigation is made on two-dimensional traffic-flow model with alternative movement and exclude-volume effect between right and up arrows. Several exact results are obtained, including the upper critical density above which there are only jamming configurations, and the lower critical density below which there are only moving configurations. The observed jamming transition takes place at another critical density p_c(N), which is in the intermediate region between the lower and upper critical densities. This transition is suggested to be a second-order phase transition, the order parameter is found. The nature of self-organization, ergodicity breaking and synchronization are discussed. Comparison with the sandpile model is made.
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  Effects of Time Reversal-Symmetry Breaking on Localization: Band Random Matrix Description

  GONG Jiangbin, XU Gong'ou

  理论物理通讯. 1999, 31(1): 91-98.

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  We investigate two kinds of band random matrix ensemble (BRM) with different time reversal symmetry, namely, BRM of complex and quaternion real (C-BRM and QR-BRM) Hermitians. Their scaling behaviors of localization are numerically studied. Results show that the removal of time reversal symmetry yields a multiplication of the localization length by a factor 2 (or, 1/2) in the absence (or, presence) of Icramers' degeneracy. This leads us, to expect a simple and universal description of the effects of time-riversal symmetry breaking on localization that the localization length ξ is given by ξ = βb²/4 where b is the band-width parameter and β the universality parameter.
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  Antiphase States in Coupled Oscillator Systems

  HU Gang, XIE Fagen, QU Zhilin, SHI pengliang

  理论物理通讯. 1999, 31(1): 99-106.

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  Coupled identical oscillators with resistive couplings are investigated. Various antiphase states are observed. The bifurcation threshojds for the antiphase states of coupled van der Pol oscillators and the unstable modes of these systems at the bifurcation points are explicitly compu ted. The dependence of antiphase states on system size and coupling length is investigated in detail. General coupled limit cycle models are also investigated. The realizations of antiphase states can be explained, based on the global potential analysis.
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  Exact Solutions of Non-Autonomous Quantum Systems with Quadratic Hamiltonian

  JIE Quanlin, WANG Shunjin, WEI Lianfu

  理论物理通讯. 1999, 31(1): 107-112.

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  Based on algebraic dynamics, we present an algorithm to obtain exact solutions of the Schrodinger equation of non-autonomous quantum systems with Hamiltonian expressed in quadratic function of creation and annihilation operators of bosons. The Hamiltonian is treated as a linear function of generators of a symplectic group. Similar to the canonical transformation of classical dynamics, we employ a set of gauge transformations to gradually transform the Hamiltonian to a linear function of Cartan operators. The exact solutions are obtained by inverse gauge transformations. When the system is autonomous, this algorithm can obtain the normal mode of the Hamiltonian, as well as the eigenstates and eigenvalues.
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  Tensor Products of Hecke Algebras

  PAN Feng, DAI Lianrong

  理论物理通讯. 1999, 31(1): 113-120.

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  Tensor product of irreducible representations of Hecke algebras are discussed. It is found that the tensor product of irreps of Hecke algebras generates representations of Birman-Wenzl algebra C_ƒ(γ, q) with γ = q³ or-q^-3. A procedure for the evaluation of tensor product coefficients (TPC's) of H_ƒ (q)oH_ƒ(q) ↓ C_ƒ(γ,q) is established when the representations of Cƒ(γ, q) remain irreducible. An example of deriving TPC's of H_ƒ (q)oH_ƒ(q) ↓ C_ƒ(γ, q) is given. It is also found that indecomposable representation of C₄(γ q) occurs in the tensor product [211]o[31].
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  Quantum Statistics for General Quadratic System

  PAN Jianwei, YU Sixia, ZHANG Yongde, SIU Gueigu

  理论物理通讯. 1999, 31(1): 121-126.

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  By the generalized linear quantum transformation theory, we concisely derive the analytic expressions of partition function for general quadratic systems of multi-mode boson and fermion Fock space without any information for the energy spectrum. Under a general condition, we firstly acquire the exact expressions of energy spectra for these systems.
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  Comparisons Between Additional Parton Evolution and Q²-Rescaling Models Based on Recombination Effect

  YANG Jianjun, LI Guanglie, Sahr Augusfine Aruna

  理论物理通讯. 1999, 31(1): 127-134.

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  Comparisons between the additional parton evolution (APE) model and Q²-rescaling (QR) model based on the recombination effect are made by means of investigating deep-inelastic (DIS) structure functions F₂^A, nuclear Drell-Yan process and nuclear gluon distributions. While explaining experimentally measured F₂^A(x) structure functions, the difference in the recombination results of the two models mainly lies in their sensitivity to input parton distributions and Q²-dependence. In predicting the nuclear Drell-Yan ratio, the APE model gives more reasonable results in the small x region than those of the QR model. The two motlels offer similar predictions of the nuclear gluon ratio G_sn(x)/G_c(x) which are extracted from the inelastic J/ψ production process.
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  Quantum Invariant Theory and Non-Adiabatic Non-Abelian Phase Factor

  FU Jian, LI Xinhua, GAO Xiaochun, GAO Jun

  理论物理通讯. 1999, 31(1): 135-140.

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  An alternative formulation is proposed for the calculation of the non-adiabatic non-Abelian connection and phase factor by making use of the invariant theory and invariantrelated unitary transformation method. In order to illustrate the formulation, we study the non-adiabatic non-Abelian phase associated with the motion of a charged particle in a timedependent magnetic field (the time-dependent Landau level problem).
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  Studies on the Chiral Order Parameter in the Schwinger Model

  LIAO Hueishih

  理论物理通讯. 1999, 31(1): 141-146.

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  Based on an analytical technique using a unitary transformation and the variational method, we study the chiral order parameter in the Schwinger model in the lattice formalism with Kogut-Susskind fermions. The fermion condensate (ψψ)fo r any coupling constant and fermion mass are calculated. Chiral symmetry is shown to be broken in the massless limit and good scaling behavior is obtained.
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  Sewing Constraints for KN Operator Formalism of Conformal Field Theories

  CHENG Qihua, WANG Jiefang

  理论物理通讯. 1999, 31(1): 147-152.

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  It is shown that in a conformal field theory on Riemann surfaces, the Krichever-Novikov (KN) operator formalism can be consistently constructed by sewing techniques for conformal field theories provided that one sewing constraint is imposed only. Moreover, the combination of sewing techniques with sewing prescription for conformal field theories gives generalization of the KN operator formalism to Riemann surfaces of genus g(>0) with one puncture or without punctures. In this way, the KN formalism has been constructed completely on Riemann surfaces.
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  Relativistic Mean-Field Approach to Infinite Nuclear Matter and Neutron Star

  SHEN Yaosong, REN Zhongzhou

  理论物理通讯. 1999, 31(1): 153-160.

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  The properties of infinite nuclear matter and neutron star are studied theoretically in relativistic mean-field (RMF) approach with three typical parameter sets NL1, NL-SH and TM1. It is found that all these new RMF parameter sets can very satisfactorily reproduce the properties of high density matter. Among these parameter sets, TM1, with a nonlinear ω term, reproduces a slightly smaller energy, piessure and neutron star mass than NL-SH and NL1. The ρ meson field has a large influence on the properties of neutron star and infinite nuclear matter. A detailed discussion for the significance of numerical results is also given.