理论物理通讯

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The Pressure-Induced Shifts of Energy Spectra of ZnS:Ni²⁺

MA DongPing, MA Ning, CHEN JuRong

理论物理通讯. 2000, 34(2): 193-200.

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The calculations of the whole energy spectrum of Zns:Ni²⁺ at normal pressure and pressure-induced shifts of its levels have been carried out on the basis of the theory of pressure-induced shifts and the diagonalization of the complete d⁸ energy matrix in a regular tetrahedral field. The calculated results are in very good agreement with experimental data at normal and high pressures. The comparison between the results of ZnS:Ni²⁺ and Mg0:Ni²⁺ indicates that the comlency of ZnS:Ni²⁺ is obviously stronger than the one of MgO:Ni²⁺;the expansion of electron wavefunctions of ZnS:Ni²⁺ under pressure is obviously larger than that of MgO:²⁺; and the pressure-induced shifts of levels of znS:NiZf show strong nonlinearity.

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Nonlinear Optical Response of a Fibonacci Multilayer

WANG RongZhou, DONG JinMing, XING DingYu

理论物理通讯. 2000, 34(2): 201-206.

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By studying numerically the light transmitting through a finite nonlinear Fibonacci multilayer, we find the gap-soliton-like phenomenon. The Fibonacci multilayer contains a Kerrtype nonlinearity in one component. When the frequency of incident light is in a stop gap, increasing the incident light intensity will make the system switch from a lower transmission state to a higher transmission state. Transmissivity for some frequencies can reach unit, which shows that they correspond to transparent states. Distribution of the field intensity in the Fibonacci structure has a particular gap-soliton-like shape, which has the multi-carrier wave.

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Temperature Dependence of Polaron Cyclotron Resonance Mass in GaAs/AlGaAs Heterostructures

WU XiaoGuang

理论物理通讯. 2000, 34(2): 207-210.

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The temperature dependence of polaron cyclotron resonance mass in GaAs/AlGaAs heterostructures is reinvestigated theoretically. By taking into account the electron-longitudinal-optic phonon interaction with temperature-dependent many-body effects, the conduction band non-parabolicity, and the influence of nonzero magnetic field, a good agreement with experiment is obtained.

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Abelian Bosonization Approach, to a Magnetic Impurity Model

ZHANG GuangMing

理论物理通讯. 2000, 34(2): 211-216.

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Abelian bosonization is applied to a magnetic impurity model, the so-called Wolff impurity model. The resulting bosonized version of the model can be solved exactly. We calculate the local dynamic spin and charge density-density correlations of the conduction electrons, and show that a quasi-particle peak in the spin-density excitations appears and becomes sharp significantly as the local interaction U grows up. The local static spin and charge susceptibilities and specific heat of the interacting electrons are also obtained, explicitly displaying a local Fermi liquid behavior.

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Tricritical Points and Reentry in the Quantum Hopfield Neural-Network Model

XI Qin, MA YuQiang

理论物理通讯. 2000, 34(2): 217-222.

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We examine a quantum Hopfield neural-network model in the presence of trimodal random transverse fields and random neuronal thresholds within the method of statistical physics. We use the Trotter decomposition to map the problem into an equivalent classical random Hopfield-type Ising model and obtain phase transitions between the ferromagnetic retrieval and the paramagnetic phases. The influence of competition between the diluted random transverse fields and the diluted random thresholds on the system is discussed, and some interesting results such as tricritical points and reentrance are analyzed.

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Spin-One Ferromagnetic Model with Anisotropic Exchange Interaction and Ds_z² Single-Ion Anisotropy

WANG Qing, CHEN TianLun

理论物理通讯. 2000, 34(2): 223-228.

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A quantum spin Heisenberg model with exchange and single-ion anisotropy is investigated by variational cumulant expansion method. Easy-axis and easy-plane cases are considered separately. Dependence of critical temperature and type of ordered phase on anisotropy parameters are examined in full detail. Thermodynamic functions are calculated for some instances.

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On the Restricted Toda and c-KdV Flows of Neumann Type

ZHOU RuGuang, QIAO ZhiJun

理论物理通讯. 2000, 34(2): 229-234.

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It is proven that on a symplectic submanifold the restricted c-KdV flow is just the interpolating Hamiltonian flow of invariant for the restricted Toda flow, which is an integrable symplectic map of Neumann type. They share the common Lax matrix, dynamical r-matrix and system of involutive conserved integrals. Furthermore, the procedure of separation of variables is considered for the restricted c-KdV flow of Neumann type.

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On the Dromion Interaction of the JMKP Equation: Equipotential Plots

RUAN HangYu, LOU SenYue

理论物理通讯. 2000, 34(2): 235-240.

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The dromion interaction of the (3+1)-dimensional conditional integrable model, Jimbo-Miwa-Kadomtsev-Petviashvilli (JMKP) system, is re-studied by means of the equipotential surface plots. The result shows that the interaction among dromions of the JMKP system is elastic which corrects the conclusion of our previous paper (J. Math. Phys. 38 (1997) 3123). firtherrnore, the interaction is also irrotational. That is to say, there are not exchanges of any physical quantities like energy, momentum and angular momentum.

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Multiboson Realizations of Lie and Quant urn Algebras

WANG XiaoGuang, JIN Yan, WANG Qi, FU HongChen

理论物理通讯. 2000, 34(2): 241-244.

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A unified method to construct the (multi-)boson realizations of the Lie and quantum algebras is proposed based on a universal deformation of boson (Heisenberg-Weyl) algebra and its multiboson realization. Some explicit examples, the Lie algebras sl(2) and su (Ill), q-boson algebra, quantum algebras sl(2)_q and su (l,l)_q, along with the q-ladder algebra are studied in detail. In particular, the square boson realizations of su (1,l) and su (l,l)_q are naturally obtained as special cases.

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Noncommutat ive Differential Calculus on Discrete Abelian Groups and Its Applications

GUO HanYing, WU Ke, ZHANG Wei

理论物理通讯. 2000, 34(2): 245-250.

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A new noncommutative differential calculus on function space of discrete Abelian groups is proposed. The derivatives are introduced with respect to the generators of the groups only. It is applied to discrete symplectic geometry and Hamiltonian systems with H(p, q) = T(p) + V(q) as well as the lattice gauge theory on regular lattice.

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The Boundary Value Problem and the Nonlinear Spatial Dispersion in Collisionless Quark-Gluon Plasma

CHEN JiSheng, LI JiaRong

理论物理通讯. 2000, 34(2): 251-260.

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The boundary value problem of the quark-gluon plasma kinetic equations is analyzed by using the derivative expansion method. The dispersion relation in the linear approximation indicates that there is no collisionless spatial damping, but it reflects that the nonlinear interaction between the eigenwaves in it is very important. By taking account of the nonlinear interactions of waves, the resonance condition between the secondary waves and the particles in quark-gluon plasma can be fulfilled which will result in the spatial damping. The nonlinear spatial collisionless damping rate for the longitudinal secondary color waves in the long wavelength limit has been calculated numerically.

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Off-Shell Propagat ion in a Quark-Gluon Plasma

ZHUANG PengFei

理论物理通讯. 2000, 34(2): 261-266.

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The off-shell propagation in a quark-gluon plasma is estimated from a quantum transport model beyond the quasi-particle approach. While our ansatz is crude concerning the properties of real quarks and gluons, it nevertheless takes very serious the basic principles of quantum field theory for non-equilibrium states.

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Pair Excitations in Even-Even Nuclei

CHEN XiaoLin, LU DaHai, YANG LiMing

理论物理通讯. 2000, 34(2): 267-272.

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A charge exchange term is added to the n-p effective interaction in treating eveneven nuclei with shape coexistence. The energy spectra and some of the E2 transition rates are calculated for ^112,114Cd, ^114,116Sn and ^118,120Te nuclei. The inclusion of this new term helps to improve an agreement with experimental data.

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E2, E4 Studies of Pd Isotopes in Microscopic sdgIBA-1

ZHANG ZhanJun, YANG Jie, LIU Yong

理论物理通讯. 2000, 34(2): 273-280.

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In sdgIBA-1, E2 and E4 transition operators of ^104-110Pd isotopes are worked out in terms of a microscopic approach. Comparisons of them with the corresponding phenomenm logical operators are made. It is found that the microscopic Hamiltonian and E2 transition operator are very close to the phenomenological counterparts while the microscopic E4 transition operator is apparently different from the phenomenological one. Calculations for the low-lying collective excitation spectra and reduced E2 (E4) transition rates are performed within the framework of the sdglBA-1. We find that the microscopic calculations reproduce the experimental data quite well, in addition, their agreement with the experimental data in general is very close to that of the phenomenological results, especially to the reduced E4 transition rates disregarding completely the apparent difference of operator.

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The Particles in Classically Forbidden Area for Exotic Nuclei in Ca Isotopes

Soojae Im, MENG Jie

理论物理通讯. 2000, 34(2): 281-288.

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Particles in classically forbidden area were studied with the Skyrme-Hartree-Fock theory for Ca isotopes from β stability line to neutron drip line. The number of neutrons in the classically forbidden area increases with mass number A, because of the increase of the number of neutrons occupied in the weakly-bound open shell. The number of protons in the classically forbidden area, in contrast, decreases with mass number A, because the orbits of protons become more tightly bound. It is shown that the number of particles in the classically forbidden area can give information on the appearance of the halo or skin.

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About the Mixing and CP Violation in Neutrino System

LIU Yong, Utpal Sarkar

理论物理通讯. 2000, 34(2): 289-294.

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Suppose that the geometrical explanation to the weak CP phase in quark sector is also valid for neutrinos, the mixing and CP violation in neutrino system are discussed. We find that a J_Cp larger than 3 × 10^-3 implies the large-mixing solution for solar neutrino problem. In the case of bi-maximal mixing, we predict relative large CP violation with J_Cp larger than 10^-3 in neutrino system, except the third mixing angle approaching to 0 or π/2 very closely.

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The Analytical Helicity Amplitudes for Z → 3γ, γγ → γZ and γZ → γγ via W-Loop, Charged Scalar-Loop

DONG FangXiao, ZHOU XianJian

理论物理通讯. 2000, 34(2): 295-300.

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The analytic helicity amplitudes of Z → 3γ, γγ → γZ and γZ → γγ via W-loop and charged scalar-loop are presented. There is some difference between our results and those in Z. Phys. C60 (1993) 175 (E.W.N. Glover and A.G. Morgan) for Z → 3γ via W-loop and fermion-loop, which has different physical meanings.

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Calculation of Vacuum Wavefunction and Mass .Gap from Improved (2+l)-Dimensional SU(2) Lattice Gauge Field Hamiltonian

LI JieMing, GUO ShuoHong, LUO XiangQian

理论物理通讯. 2000, 34(2): 301-306.

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The truncated eigenvalue equation of SU(N) lattice gauge theory is studied by using improved lattice gauge Hamiltonian with a proper truncation scheme that preserves the continuum limit. The calculations of vacuum state wavefunction and glueball mass of (2+1)-dimensional SU(2) theory up to third order are carried out, the results show the improvement of scaling behavior in deep weak coupling region.

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Noncommutative Differential Calculus Approach to Discrete Symplectic Schemes on Regular Lattice

GUO HanYing, WU Ke, WANG ShangHu, WANG ShiKun, WE1 GongMin

理论物理通讯. 2000, 34(2): 307-316.

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By means of a noncommutative differential calculus on function space of discrete Abelian groups and that of the regular lattice with equal spacing as well as the discrete symplectic geometry and a kind of classical mechanical systems with separable Hamiltonian of the type H(p, q) = T(p) + V(q) on regular lattice, we introduce the discrete symplectic algorithm, i.e., the phase-space discrete counterpart of the symplectic algorithm including original symplectic schemes and the jet-symplectic schemes in terms of the discrete time jet bundle formalism, on the regular lattice. We show some numerical calculation examples and compare the results of different schemes.

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Numerical Studies on the Formation of Magnetic Loops

WANG ChuanBing, ZHENG HuiNan, WANG Shui

理论物理通讯. 2000, 34(2): 317-320.

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The formation of a current-carrying non-force-free magnetic loop is studied by threedimensional magnetohydrodynamic simulation. The effects of the plasma pressure and the gravitational force are considered for the first time. The results show that the twist motion of the footpoints of magnetic field lines at the photosphere will form magnetic loop in the corona. The magnetic loop expands mainly in both the vertical and horizontal directions along the magnetic neutral line at the photosphere bases.

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Dispersion-Modified Burgers Description for Nonlinear Surface Wave Excitations in Bénard-Marangoni Convection

HUANG GuoXiang, M.G. Velarde

理论物理通讯. 2000, 34(2): 321-326.

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The evolution of long nonlinear surface wave excitations in a Bénard-Marangoni shallow liquid layer is studied when the system is far from its instability threshold. For (M -M_c)/M_c = 0(1), thus for surface wave excitations with possible large amplitude, where M is the Marangoni number of the system and M_c is its critical value bifurcating to oscillatory convecting state from a motionless one, the surface wave displacement is found to obey a dispersion-modified Burgers equation whose kink-like solutions are also studied.

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Diagonalizat ion of Multi-Oscillat or Models and Level-Spacing Distributions

BAI ZhiMing, LIU JingSong, GE MoLin

理论物理通讯. 2000, 34(2): 327-336.

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Three-body oscillator in three-dimensional space is exactly solved and its levelspacing distribution P(s) is studied. Multi-coupled oscillator can also be diagonalized with its level-spacing distribution discussed. It is found that P(s) is very unstable and it is connected tightly with the parameters of the system.

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Solution for One-Dimensional Quantum Oscillator with Time-Dependent Frequency and Mass

XU XiuWei, HOU Guang, ZHANG YongDe

理论物理通讯. 2000, 34(2): 337-340.

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Based on the generalized linear quantum transformation theory, we present a normal ordering evolution operator for onedimensional quant urn oscillator with time-dependent frequency and mass, then give the exact expression of the evolution matrix elements, wave function and expectation value of arbitrary observable.

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On the Entangled State Representation with Continuum Variables

FAN HongYi

理论物理通讯. 2000, 34(2): 341-344.

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we propose the conception of entangled state representation with continuum variables. We analyze the non-factorizable properties of the |η> state, the common eigenvector of two-particle relative position and total moment um (Fan Hongyi and J.R. Klauder, Phys. Rev. A49 (1994) 704), and recast it into the standard form as the state prepared in a parametric down conversion process which involves the entanglement of idle and signal photons. We name the set of |η> as entangled state representation, as it is orthonormal and complete

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Trapping States for a Three-Level Atom in the A Configuration

YANG XiaoXue, ZHAN Ling, QU ZhaoJun, WU Ying

理论物理通讯. 2000, 34(2): 345-348.

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A simple scheme has been developed for seeking atomic trapping states for a cornposite system consisted of a three-level atom interacting with two quantized laser modes in the A configuration. A series of new trapping states (also called as dark states) are discovered and their analytical expressions are explicitly obtained.

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Gravitational Lensing of Fermion Stars

LIU DaHai, ZHANG YuanZhong, ZHU ZongHong

理论物理通讯. 2000, 34(2): 349-358.

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We discuss the fermion stars, the self-gravitating systems of Fermi gases, as possible gravitational lenses. It is supposed that the fermions interact with themselves and other particles only by gravity, so they are the candidates of dark matter. We calculate Einstein deflection angles, study the image configurations, and calculate the magnification factors for a number of fermion stars that range from strong relativistic configurations to nonrelativistic ones. We find that typically there are three images, one Einstein ring and one radial critical curve for both cases. Two of the images are within the Einstein ring, and the other is outside, which may be very far. All these lensing characteristics can help to identify fermion stars as potential lensing objects, thus might give direct evidence that dark fermion stars exist in the universe.

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Size and Configuration Effect on Ion Transport of Biological Membrane

ZHANG LingYun

理论物理通讯. 2000, 34(2): 359-364.

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The theoretical model of the ion channel is described and the conductivity mechanism on the single ion channel of biomembrane has been discussed. By starting with the Boltzmann equation, we obtain the distribution function of ions in the single channel and the expression of electric current in the case of the cylindrical symmetry. Our model takes into account the selectivity for,different ions and supports the binding site model. It has been shown that the interaction between the ion and the protein and water environment in biomembrane is the key factor. The theoretical relation of current-voltage is in agreement with the experimental values.

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Applications of Backlund Transformations to Explicit and Exact Solutions in Nonlinear Wave. Equations

YAN ZhenYa, ZHANG HongQing

理论物理通讯. 2000, 34(2): 365-368.

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Bäcklund transformations and heat equation are used to find several families of explicit and exact solutions for the well-known Whitham-Broer-Kaup equations in shallow water and Kupershmidt equations. In result, multi-soliton solutions, rational fraction solutions and soliton-like solutions are obtained.

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Vacuum Condensates from the Modification of Global Color Symmetry Model

ZONG HongShi, LÜ XiaoFU, GU JianZhong,CHANG ChaoHsi, ZHAO EnGuang

理论物理通讯. 2000, 34(2): 369-372.

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Based on the quark propagator in the instanton dilute liquid approximation, we have determined the quark condensate , the mixed quark gluon condensate g,_μνσ^μνq) and the four-quark condensate at the mean-field level in the framework of global color symmetry model. The numerical calculation shows that our result is compatible with the range obtained within other nonperturbative approaches. In particular, we have found that even at the mean-field level the naive vacuum saturation approximation is not a good approximation when we consider nonlocal four-quark condensate.

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Coordinate SchrSdinger Representation of Squeezing Operator for Scalar Field Gained via the IWOP Technique

FAN HongYi, FAN Yue

理论物理通讯. 2000, 34(2): 373-376.

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By deriving the Fock representation of Schrödinger field operators' eigenvectors and using the technique of functional integration within an ordered product of operators we provide a direct route to obtaining normally ordered squeezing operator for scalar field, which is mathematically concise and physically appealing. The coordinate Schrödinger representation of field squeezing operator is then obtained.

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On K-Factor's Non-Constancy for the Drell-Yan Process in Carbon-Carbon Nuclear Collision

HOU ZhaoYu, ZHENG Qiao, DUAN ChunGui, ZHANG BenAi

理论物理通讯. 2000, 34(2): 377-380.

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The double Q²-rescaling model is used to compute the change of K-factor with x_A2 when the nucleus carbon-nucleus carbon collision occurs at different values of x_Al, where x are momentum fraction variables. In the calculation, the contributions of annihilations and Compton scattering have been considered for the Drell-Yan process. The calculated results show that the plots of K-factor versus X_A2 are very different for different values of x_Al. They are also compared with experimental data, which provides a test to the model of nuclear effect and the QCD theory itself

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Quantum Nondemolition Measurement of Photon-Number Distribution for a Two-Mode Field

ZHENG ShiBiao

理论物理通讯. 2000, 34(2): 381-384.

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We propose a quantum nondemolition measurement of the photon-number distribution for a two-mode cavity field. In the scheme two sequences of two-level atoms interact dispersively with the respective cavity modes and resonantly with two classical fields, and then are detected continually. The field finally reduces to a two-mode Fock state. The probability of collapsing to a given Fock state is determined by the initial photon-number distribution. The scheme can be easily generalized to a field with N modes.

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2000年, 第34卷, 第2期　
刊出日期：2000-09-15

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2000年, 第34卷, 第2期 刊出日期：2000-09-15

2000年, 第34卷, 第2期　
刊出日期：2000-09-15