理论物理通讯

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Analytical Solutions of a Trapped Ultracold Ion Experiencing a Travelling Wave Laser without Rotating Wave Approximation

FENG Mang, FANG XiMing, ZHU XiWen, SHI Lei, GAO KeLin

理论物理通讯. 2000, 34(1): 1-4.

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In coherent state representation and in the absence of rotating wave approximation,the analytical forms of the eigenenergies and eigenfunctions of a trapped ultracold ion interactingwith a travelling wave laser are presented for some particular detunings. The differencebetween the standing wave laser and the travelling one radiating a trapped ultracold ion isalso pointed out.

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The Ground State and the Structure of the Ground Rotation Band of H₃⁺-Like Molecular Ions

HE YanZhang, BAO ChengGuang

理论物理通讯. 2000, 34(1): 5-10.

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In addition to the well-known quantum numbers, the total spin as a good quantumnumber has also been introduced to classify the eigenstates of the H₃⁺-like systems. Thedegeneracy of the ground state and the structures of the ground rotation bands have beendeduced based on an ab initio symmetry consideration.

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Effects of Pressure on Doped Kondo Insulators

ZHANG Sun, LI ZhengZhong, XU Wang, XU XiaoHua

理论物理通讯. 2000, 34(1): 11-20.

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The effects of pressure on the doped Kondo insulators (KI) are studied in theframework of the slave-boson mean-field theory under the coherent potential approximation.A unified picture for both the electron-type KI and hole-type KI is presented. The density ofstates of the f -electrons under the applied pressures and its variation with the concentrationof the Kondo holes are calculated selficonsistently. The specific heat coefficient, the zerotemperaturemagnetic susceptibility as well as the low-temperature electric resistivity of thedoped KI under various pressures are obtained. The two contrasting pressure-dependent effectsobserved in the doped KI systems can be.naturdy explained within a microscopic model.

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The Charged and the Spin-Excitation Gaps in the Double-Exchange Model: a Rigorous Result

WANG JiGang, TIAN GuangShan

理论物理通讯. 2000, 34(1): 21-30.

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We extend a previous result of ours [G.S. Tian, Phys. Rev. B58 (1998) 76121 on the charged gap and the spin-excitation gap of the half-filled Kondo lattice model to the doubleexchange model. In our original approach, this model cannot be dealt with since its localized spins have a large spin number S=3/2. By following a construction argument due to Zener and rewriting the double-exchange Hamiltonian, we are able to overcome this difficulty and re-establish the same relation for this model.

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Energy Spectrum and Its Pressure-Induced Shift and J-T Effect of ZnTe:Mn²⁺

MA DongPing, WU Ye, CHEN JuRong, MA Nin

理论物理通讯. 2000, 34(1): 31-38.

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By using strong-field scheme, the complete d⁵ energy matrix with symmetry has been constructed. Then, by diagonalization of this matrix at normal and various pressures,the whole energy spectrum [including the ground-state zero-field splitting (GSZFS)] and its pressure-induced shift (PS) of Znlb:Mn²⁺ have uniformly been calculated. The results are in very good agreement with experimental data. According to the eigenfimctions and PS, the assignments of four absorption bands have been given. By taking into account the dect of different deformations of t₂ and e radial wavefunctions on t₂³(⁴A₂)e²(³A₂)⁴ A₁ and t₂³(²E)e²(³A₂)⁴E, the position of the third absorption band at normal pressure has been estimated.The tetragonal field is important for GSZFS of ZnTe:Mn²⁺ and its PS, which supports the existence of tetragonal Jahn-Teller distortion in ZnTe:Mn²⁺ The physical essentials of typical levels, GSZFS and their PS have been revealed.

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The Influence of the Electron Effective Mass Mismatch on the Intraband Optical Transition in a Semiconductor Superlattice

ZHENG YiSong, WU HongZhu, Lü TianQuan, PAK Hak Chol

理论物理通讯. 2000, 34(1): 39-42.

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The effective mass mismatch of a conduction band electron in a semiconductor.superlattice renormalizes the electron confining potential. Taking this effect into account we calculate the absorption coefficient of the intraband optical transition in an InGaAs/InAlAs superlattice. We find that the electron effective mass mismatch causes a notable broadening of spectrum linewidth, which can well account for the experimental result.

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Structural Dependence of Electronic and Magnetic Properties of the Cr₁₃ Cluster

LUO YouHua, SUN HouQian, ZHAO JiJun, WANG GuangHou

理论物理通讯. 2000, 34(1): 43-46.

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A tight-binding effective potential has been employed, in conjunction with a genetic algorithm, to fully optimize the Cr₁₃ cluster geometry without imposing any symmetry constraints. The minimum energy structure of this cluster is found to be a slightly distorted icosahedron. Based on the optimized structure and three assumed geometries (icosahedron,bcc-like and fcc-like), the structural dependence of electronic and magnetic properties of the Cr₁₃ cluster is discussed by using a d-band Hubbard-like Hamiltonian in the unrestricted Hartree-Fock approximation. Results are given for the average magnetic moment and local magnetic moments. It is found that for all considered geometries the Cr₁₃ cluster exhibits antiferromagnetic behavior. Results are also given for the cohesive energy, average coordination number, and local electronic densities of states. The results indicate that the average coordination number per atom in the cluster geometry is a significant factor to affect the magnetism.Also, the local density of states is a sensitive function of geometry.

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d-Dimensional Kinetic S⁴ Model

ZHU Jian Yan, YANG ZhanRu

理论物理通讯. 2000, 34(1): 47-54.

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A single-spin transitional critical dynamics based on the Glauber theory is used to investigate the d-dimensional kinetic S⁴ model. We derive the fundamental dynamical equations by a cumulant expansion, and then, a one-dirnensional model is treated. We obtain approximately the local magnetization and equal-time spin-pair correlation function, in which the terms of k₃ and the higher orders are ignored (corresponding to high-temperature cutoff). These are finally extended to d-dimensional case. In addition, we obtain the critical point k_c of d-dimensional S⁴ model, and give a relation satisfied by the dynamic critical exponent Z and the correlation length critical exponent ν.

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On the Mobility of a One-Dimensional Damped Frenkel-Kontorova Chain: Commensurate Versus Incommensurate

ZHANG ShuDong, HU BamBi

理论物理通讯. 2000, 34(1): 55-62.

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The mobility of a,one-dimensional damped fienkel-Kontorova chain under a dcdriving force is studied numerically and analytically. For the commensurate case, the particles in the chain are synchronized at high driving force. For the incommensurate chain, a single mode solution dominates at high mobility regime. We are able to calculate the mobilities for both the cases analytically, and a good agreement with numerical results is found. The mobility hysteresis for the incommensurate chain is explained by the existence of two branches of physical solutions, and transitions occur when one of them breaks up.

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A Neural Network Model with Self-organizing Pulse-Coupled Oscillator

GU YuQiao, CHEN TianLun, HUANG WuQun

理论物理通讯. 2000, 34(1): 63-68.

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We consider a two layered neural network in which the second layer is composed of simple pulse-coupled neuronal oscillators connected by excitatory and inhibitory lateral interaction weights. For storing information' a self-organizing learning algorithm with respect to the amplitude of the neuronal oscillators is introduced. The dynarnical behavior and the retrieval ability of information of this model are analyzed. Computer simulation shows that the learning can enhance the coherent characteristic of the neuronal activities and the dynamical behaviors of this model in pattern recognition are similar to the dynarnical process in biological neural system and perform information retrieval property to stored patterns.

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A Three-Josephson-Junction Device with Noise

LI JingHui, XING DingYu, DONG JinMing

理论物理通讯. 2000, 34(1): 69-76.

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A Gaussian white noise model and a symmetric dichotomous noise model for a three-Josephson-junction device are studied. It is shown that the symmetric noise can produce net voltage (Its corresponding dc current is zero), which sterns from the multiplicative noise,the asymmetry of the potential or the asymmetry of the potential itselt; respectively for the Gaussian white noise model or for the dichotomous noise model. The net voltage is negative,and exhibits a peak with increasing the additive noise strength (the stochastic resonance). The dc current-voltage characteristics are calculated for the two models. In addition, we find that when the dc current is not zero, in some scope the absolute value of the dc voltage versus the additive noise strength also presents the stochastic resonance.

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Gauss Decomposition of Dynamical Elliptic Algebra A_q,p,π(gl_n)

HOU BoYu, FAN Heng, YANG WenLi, CAO JunPeng

理论物理通讯. 2000, 34(1): 77-82.

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We propose a dynamical elliptic algebra

which is based on the relations RLL = LLR^*, where R and R^* are the dynamical R-matrices of A_n-1⁽¹⁾-type face model with the elliptic module shifted by the center of algebra. nom the high-rank Gauss decomposition,h we obtain the Drinfeld currents of dynarnical elliptic algebra

.

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A New Asymptotic Approach to Solve Nonlinear Evolution Equations

RUAN HangYu, LOU SenYue, CHEN YiXin

理论物理通讯. 2000, 34(1): 83-90.

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A conformal-invariant asymptotic expansion approach to solve any nonlinear integrable and nonintegrable models with any dimensions is proposed. Taking the compound KdV-Burgers (cKdVB) equation and the KdV-Burgers (KdVB) equation as concrete examples,we obtain many new conformal-invariant models with Painleve' property and the approximate solutions of the cKdVB and KdVB equations. In some special cases, the approximate solutions become exact.

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Massive Meson Fluctuation in NJL Model

HUANG Mei, ZHUANG PengFei, CHAO WeiQin

理论物理通讯. 2000, 34(1): 91-100.

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Based on the self-consistent scheme beyond the mean-field approximation in the large N_c expansion, including current quark mass explicitly, a general scheme of SU(2) NJL model is developed. To ensure the quark self-energy expanded in the proper order of N_c,an approximate internal meson propagator is deduced, which is in order of O(l/N_c). In our scheme, adopting the method of external momentum expansion, all the Feynman diagrams are calculated in a unified way by only expanding the quark propagator. Our numerical results show that, different &om the mean-field approximation in which the explicitly chiral symmetry breaking is invisible, the effect of finite pion mass can be seen clearly when beyond the meanfield approximation.

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Antiparticle Excitation Effect in the Relativistic Spin-Isospin-Dependent Response Function of Nucleus

LIU LiangGang, CHEN Wei, LUO XiangQian, Masahiio Nakano

理论物理通讯. 2000, 34(1): 101-106.

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The spin-isospin-dependent response function of nucleus is studied in the relativistic formalism. Besides the well-known relativistic particlehole and A-hole excitations, the antiparticle excitations such as nucleon-antinucleon, nucleon-antidelta, antinucleon-delta excitations are also taken into account in the calculation of the response function, and the effect of the antiparticle excitation is emphasized. The antiparticle excitation enhances the response function and its effect to the response function is largely determined by the cutoff parameter which is introduced by the need of the renormalization. The position of the peak of the A-hole resonance is mainly dominated by short range correlation Landau-Migdal parameter g', and we find g' is about 0.6. The effect of two-nucleon absorption and projectiletarget form factor are also studied.

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Hamiltonian Approach to Meson Structure in Extended Nambu-Jona-Lasinio Model

DENG WeiZhen, YANG LiMing

理论物理通讯. 2000, 34(1): 107-114.

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The Nambu-Jona-Lasinio model,is extended to inclusion of the nonlocal effective quark interaction with confinement. An effective Hamiltonian in the instantaneous approximation is used to study meson properties in the random phse approximation.

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Neutralino Pair Production at Proton-Proton Collider

HAN Liang, MA WenGan, JIANG Yi, ZHOU MianLai, ZHOU Hong

理论物理通讯. 2000, 34(1): 115-122.

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We investigated the Drell-Yan process of the light neutralino pair

(i, j = 1, 2) productions at hadron colliders. We studied the dependence of the coupling properties of two light neutralinos

on, three SUSY Lagrangian parameters M₁, M₂ and μ, and find that the production rate of

pair will be dominated by the Higgsino-like couplings under the conditions p << M₂ and μ～M₁.

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Cosmological Relics of the High Energy Cold Dark Matter Particle in the Universe

LI XueQian, TAO ZhiJian

理论物理通讯. 2000, 34(1): 123-128.

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We demonstrate that if the universe is dominated by the massive cold dark matter, then besides the generally believed thermal distribution of the dark matter relics, there may exist some very energetic nonthermal relics of the dark matter particles in the universe from some unknown sources, such as from decay of supermassive X particle released from topological defect collapse or annihilation. Very interesting, we point out that these high energy dark matter particles may be observable in the current and future cosmic ray experiments.

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Associated J/ψ+γ Production Through Double Pomeron Exchange: the Nature of the Pomeron and Hard Diffractive Factorization Breaking

XU JiaSheng, PENG HongAn

理论物理通讯. 2000, 34(1): 129-134.

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We present a study of associated J/ψ+γ production through double pomeron exchange at energies reached at the Fermilab Tevatron.and CERN LHC based on the Ingelman-Schlein model for hard difiactive scattering and the factorization formalism of nonrelativistic QCD for quarkonia production. We find that the process p+p→p +p + J/ψ+γ + X can be used to probe the gluon content of the pomeron and study the nature of hard difiactive factorization breaking.

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Aharonov-Bohm Scattering on Thin Toroidal Magnetic Flux Without Toroidal Shielding

QIAN ShangWu, GU ZhiYu, MIA0 ChunHui

理论物理通讯. 2000, 34(1): 135-142.

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This paper gives a rigorous and explicit calculation of the scattering wavefunction for the case of a bare thin toroidal magnetic flux, i.e. a thin toroidal magnetic flux without toroidal shielding.

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Brownian Motion of the Quantum Dissipation in the RWA

GAO YiBo

理论物理通讯. 2000, 34(1): 143-148.

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A microscopic approach treating the quantum dissipation process presented by Sun and Yu (Phys. Rev. A49 (1994) 592; A51 (1995) 1845) is invoked to construct the wavefunction of the composite system——the model for a harmonic oscillator interacting with a many-oscillator bath under the rotating wave approximation. It shows the back-action of the system on the bath. In particular, the dynamic evolution of the wavefunction for the composite system maintains a factorized form in its wavefunction. In the limited temperature, the reduced density matrix for the system is also calculated to clarify the influence of Brownian motion on the system.

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Normally Ordered Operator Fredholm Equation and Its Applications in Quantum Mechanics

FAN HongYi, FAN Yue

理论物理通讯. 2000, 34(1): 149-154.

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By virtue of the technique of integration within an ordered product of operators we construct the normally ordered operator fiedholm equation. We use it to derive some new operator formulas. For Weyl correspondence, operator fiedholm equation can also be constructed. Some applications of the operator Fkedholm equation are given.

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Interaction of Negative Binomial States with Two-Level Atoms

WANG XiaoGuang, FU HongChen

理论物理通讯. 2000, 34(1): 155-160.

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We study the interaction of negative binomial states with two-level atoms. The dynamical evolutions of atomic population inversion, field entropy, Q function, and phase distribution are investigated in detail. The field becomes a superposition of negative binomial states at certain times, and this is confirmed further by its photon number distribution.

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Output Field of the Excitons in a Microcavity Under the Finite Temperature

LIU YUXi, WEI JiKun, KANG XiuYin

理论物理通讯. 2000, 34(1): 161-166.

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We use the Fokker-Planck equation and stochastic differential equations to study the composite system of the cavity field and the excitons under the finite temperature. The conditions for the stability of the system are given. The effect of reservoir phonons on the quadrature squeezing spectra of the output field is discussed by using small fluctuation a pproximation. We find that the perfect squeezing of the output field appear; at two points under the same condition comparing with the case of zero temperature.

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Newman-Penrose Formalism and Gravitational Impulsive and Shock Waves

HUANG ZhenXing, KUANG ZhiQuan, LIANG CanBin, WU XiaoNing

理论物理通讯. 2000, 34(1): 167-172.

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Vacuum spacetimes endowed with two commuting spacelike Killing vector fields are considered. Subject to the hypothesis that there exists a shearfree null geodesic congruence orthogonal to the two-surface generated by the two commuting spacelike Killing vector fields,it is shown that, with a specific choice of null tetrad, the Newman-Penrose equations are reduced to an ordinary differential equation of Riccati type. fiom the consideration of this differential equation, exact solutions of the vacuum Einstein field equations with distribution valued Weyl curvature describing the propagation of gravitational impulsive and shock wave of variable polarization are then constructed.

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The Evolution for Various Matter Perturbations in the Expanding Universe

LIN WenBin, SHENG Ke, CHU YaoQuan

理论物理通讯. 2000, 34(1): 173-178.

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We present a systematic treatment of the linear theory of scalar gravitational perturbations of various matter (including baryons, cold dark matter, photons, massless neutrinos,and massive neutrino) for the flat, open and close universes, concentrating on the treatment of the massive neutrino component which has been either ignored or approximated crudely for the nonflat universe in previous literatures.

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Analytic Study of XY-Ising Model

CHEN HuaSheng, ZHU YunLun

理论物理通讯. 2000, 34(1): 179-180.

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We apply the variational cumulant expansion to study the phase transition of a two-dimensional coupled XY-king model. This model can describe several different systems with underlying continuous and & symmetries. We calculate the free energy, internal energy and specific heat to the third-order approximation with the trial action of two variational parameters. A comparison with Monte Carlo data is also presented.

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B?cklund Transformation and Solutions for the Long-Wave and Short-Wave Resonance Equations and Their Extending System

TIAN YongBo

理论物理通讯. 2000, 34(1): 181-184.

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By using Painlevé analysis, we derive the Backlund transformation for the longwave and short-wave resonance equations and their extending systems. Then we take some constraints of the B?ckJund transformation and find some solutions.

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The Moving Law of the Scroll Wave Filament

ZHOU TianShou, ZHANG SuoChun, ZHENG ZuoHuan

理论物理通讯. 2000, 34(1): 185-188.

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We investigated the moving law of the scroll wave filament by perturbation arguments,and obtained that, when the normal direction of scroll wave front curve surface is similar to that of its filament, the normal speed (noted by α ) of the filament is relative not only to the curvature (k) of the filament, but also to that k₁ of scroll wave front curve surface,i.e., a = εD(k -k₁) (where D is diffusional coefficient), and irrelative to the characteristic speed of excitable media. Besides, we also investigated the moving law of the filament along the axis direction, and obtained the similar result to that of Keener's (J.P. Keener, Physica D31 (1988) 269).

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Infinitely Many Lax Pairs of the Korteweg-de Vries Equation

YU Jun

理论物理通讯. 2000, 34(1): 189-192.

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Starting from a known Lax pair, one can get some infinitely many coupled Lax pairs.In this letter, we take the well-known KdV equation as a typical example. Using infinitely many symmetries, the infinitely many inhomogeneous linear Lax pairs of KdV equation can be obtained. And considering the Darboux transformations for the KdV equation leads to the infinitely many inhomogeneous nonlinear Lax pairs.

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2000年, 第34卷, 第1期　
刊出日期：2000-07-30

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2000年, 第34卷, 第1期 刊出日期：2000-07-30

2000年, 第34卷, 第1期　
刊出日期：2000-07-30