2000年, 第33卷, 第1期　
刊出日期：2000-01-30

  

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  A Uniform Semiclassical Calculation of the Rings in Photodetachment Microscope

  YANG GuangCan, DU MengLi

  理论物理通讯. 2000, 33(1): 1-6.

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  We describe a uniform semiclassical theory for the spatial distribution of the photodetached electron of H^- in the presence of a static electric field. In this theory we propagate the photodetached electron wavefunction using a mixed position and momentum coordinate method to large distance where a uniform approximation to the electron flux distribution is calculated. Details are given for the propagation of the mixed coordinate wavefunction with cylindric symmetry and the transformation between configuration space wavefunction and the mixed position and momentum wavefunction.
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  Initial Phase Dependence of the Soliton Decay Rate for the Nonlinear Schrodinger Equation with a Lossy Term

  LOU SenYue

  理论物理通讯. 2000, 33(1): 7-10.

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  By using a recursion relation from the x-discrete nonlinear Schrödinger equation with a "lossy" term, we prove that the solitons propagate along the fiber in the decay rate exp -(I+ M₀)Γx if the "initial" input phase (at x = 0) is taken as the form M_oΓt²/2α_l. The same conclusions can also be obtained from the exact numerical calculations.
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  Efficient State Preparation via Ion Trap Quantum Computing and Quantum Searching Algorithm

  ZENG HaoSheng, KUANG LeMan

  理论物理通讯. 2000, 33(1): 11-14.

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  We present a scheme to-prepare a quantum state in an ion trap with probability approaching to one by means of ion trap quantum computing and Grover's quantum search algorithm acting on trapped ions.
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  Localization in the Non-analytic Quantum Kicked Systems

  LIU Jie, CHENG TaiWang, CHEN ShiGang

  理论物理通讯. 2000, 33(1): 15-20.

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  Numerical investigations on non-analytic quantum kicked systems are presented. A new type of localization - power-law localization is found to be universal in the nonanalytic systems. With increasing the perturbation strength, a transition from perturbative localization to pseudo-integrable system, to dynamical localization and to complete extension is clearly demonstrated. The dependence of the localization length on perturbation is given in different parameter regimes.
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  Leading Supersymmetric Electroweak Corrections to Top Quark Decay into a Neutralino and Light Stop

  YANG YaSheng, LI ChongSheng, CAO QingHong, LIU HongXuan

  理论物理通讯. 2000, 33(1): 21-26.

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  We calculate the leading supersymmetric electroweak corrections to t → t₁x_j0 using dimensional reduction scheme within an approximation of low tan β, which can easily be extended to t→x_jb_i. The numerical results show that such corrections can exceed -12% for tan β = 2 and -6% for tan β = 11, respectively. And these corrections vary insensitively with mi, in the region allowed by the kinematics except for ones near the threshold.
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  Calculation of Electric Mult ipole Moment Integrals Using Translation Formulas for Slater-Type Orbitals

  I.I. Guseinov, B.A. Mamedov, M. Orbay, T. Özdogan, A.M. Rzaeva, A.G. Gasanov

  理论物理通讯. 2000, 33(1): 27-32.

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  Using translation formulas for Slater-type orbitals the infinite series through the overlap integrals are derived for the electric multipole moment integrals. By the use of the derived expressions the electric multipole moment integrals, and therefore, the electric properties of molecules can be evaluated most efficiently and accurately. The convergence of the series is tested by calculating concrete cases. An accuracy of for 10^-5 the computer results is obtained for 1 ≤ v ≤ 5, and for the arbitrary values of internuclear distances and screening constants of atomic orbitals.
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  Ionization Dynamics of 1D Model Atom in Ultra-Strong lω-2ω Laser Fields

  CHENG TaiWang, LIU Jie, CHEN ShiGang

  理论物理通讯. 2000, 33(1): 33-38.

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  We investigate the ionization dynamics of 1D model atom in ultra-strong dichromatic lω-2ω laser fields with a constant phase difference. We find numerically that both the total ionization and the distribution between forward and backward rates show clear phasedependent character. This phenomenon can be explained by the first-order high frequency Floquet theory. Finally, this phase-dependent character is testified u;ith pulsed laser fields provided the pulse is smoothly (adiabatically) turned on.
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  The Relation Between Elastic and Total Scatterings from Fractals

  LI Heng, TAO RuiBao

  理论物理通讯. 2000, 33(1): 39-42.

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  The ratio of the elastic and total scattering intensities η(q) = I:(q)/I_t²(q) is studied for fractals of dimension range widely. The results show that it oscillatorily decays with a quantity qR_o where q is the absolute value of the momentum transfer q and R_o the average distance between the nearest neighbor sites of scatters in fractal objects. The locations of valleys and peaks of η are only dependent on fractal dimensions. However, the dependence is very beak and η is almost a constant varying in the range of only several percent for widely different fractal dimensions.
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  Nonlinear Transport of Three-Dimensional Electron Gases Under the Influenceo f an Intense Terahertz Radiation

  CHEN YiQiao, LIU ShiYong, LEI XiaoLin

  理论物理通讯. 2000, 33(1): 43-48.

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  We present a detailed theoretical and numerical investigation on nonlinear transport of a model three-dimensional electron gas driven by an intense terahertz (THz) radiation at lattice temperature T = 10,77,300 K using the conventional and recently developed balanceequation approach. Ionized-impurity, acoustic-phonon and polar optical-phonon scatterings were taken into account for electrons in a single parabolic band. The heating of electrons and the suppression of the dc electron mobility by the irradiation of the intense THz field are predicted. We find that the dc average mobility of electrons peaks around a certain value of the amplitude of the ac field at low lattice temperature.
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  Interface Phonons in Cone-Shaped GaAs/Al_xGa_l-xAs Quantum Dots with a Spherical Top Surface

  QI YongChang

  理论物理通讯. 2000, 33(1): 49-54.

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  By using the dielectric continuum model, the side interface optical (SIO) and top interface optical (TIO) phonon modes for a cone-shaped GaAs/Al_xGa_l-xAs quantum dot with a spherical top surface are obtained. It is found that, unlike the TI0 mode which shows the same results as those for spherical GaAs/Al_xGa_l-xAs quantum dots, the SIO phonon frequencies depend on not only the integer l, but also the integer |m| as well as the polar angle α, and the frequency behavior of all the different modes is also strongly dependent on x. It is useful to study the couplings between electrons and phonons for those like this system.
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  Influence of Interface Scattering and Quantum Size Effect on the Giant Magnetoresistance in a Magnetic Sandwich Structure

  DONG ZhengChao

  理论物理通讯. 2000, 33(1): 55-62.

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  An analytical Green's function approach to the study of the electronic transport in a magnetic sandwich structure is presented. Taking into account the quantum size effect and considering three types of scattering from bulk impurities, rough surface, and two rough interfaces, we calculate the one-particle Green's function and the in-plane conductivity, yield a new formula for conductivity. It is found that (i). the magnetoresistance in the ultrathin spin-value sandwiches shows oscillation as a function of thickness with a period of half Fermi wavelength; (ii) in the thin-film limit and the lowest-order approximation of the surface and interface scatterings, the total conductivity is given by a sum of conductivities of all the subbands and the two spin channels, for each subband and each spin channel the scattering rates due to the impurities, surfaces and interfaces are additive.
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  The Gaussian Model on the Inhomogeneous Fractal Lattices

  KONG XiangMu, LI Song

  理论物理通讯. 2000, 33(1): 63-68.

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  The decimation real-space renormalization group and spin-rescaling methods are applied to the study of phase transition of the Gaussian model on fractal lattices. It is found that the critical point K^* equals b/2 ( b is the distribution constant of Gaussian model) on nonbranching Koch curves. For inhomogeneous fractal lattices, it is proposed that the b is replaced with b_qi (qi is the coordination number of the site i) and satisfies a certain relation b_qi/b_qj = q_i/q_j. Under this supposition we find that the critical point of the Gaussian model on a branching Koch curve can be expressed uniquely as K^* = b_qi/q_i.
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  Density Matrix and Squeezed State for Two Harmonic Oscillators with a Kinetic Coupling

  FAN HongYi, ZHANG Ying

  理论物理通讯. 2000, 33(1): 69-74.

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  We study two harmonic oscillators with a kinetic coupling system. By taking a unitary transformation approach, we turn the system into the Fock space of two independent harmonic oscillators and derive the density matrix for it. The corresponding unitary operator U is characteristic of including frequency-jump squeezing transformation. By virtue of the technique of the integration within an ordered product of operators, we manifestly show that the ground state of the system is a squeezed state.
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  The Restricted Boussinesq Flows, Their Lax Representations and r-Matrix

  ZHOU RuGuang

  理论物理通讯. 2000, 33(1): 75-80.

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  We present the Lax representations for the restricted Boussinesq flows resulted from the binary nonlinearization,of Lax systems of Boussinesq equation. Furthermore we show this Lax operator satisfies the T-matrix relation. Thus 3N involutive integrals for restricted Boussinesq flows are obtained.
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  Spectra of Halo Nuclei

  WANG ZhengDa, WANG XiaoBin, WANG XiaoChun, ZHANG XiaoDong

  理论物理通讯. 2000, 33(1): 81-86.

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  Based on the self-similar-structure shell model a size resonance model, which includes the size resonance of halo neutron orbit and the correlation size resonance of core surface, is proposed. In terms of the size resonance model the excited spectra and the soft dipole resonances for ¹¹Be and ¹¹li are reproduced.
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  Liquid Model of Phase Transition from Quark-Gluon Phase to Hadron Phase on Analogy of BCS Theory

  Kazuo Harada, Masanori Matsuda, ZHENG YuMing

  理论物理通讯. 2000, 33(1): 87-92.

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  A phenomenological model of the transition from quark-gluon phase to hadron phase is presented on the analogy of BCS theory. The massive current-quarks constitute the quark Cooper-pair, i.e., the hadron at T_c = 150~200 MeV, The order parameter of qq-pair takes a value in the range from 0.4 to 0.2 GeV. An experimental verification method of the present model in the heavy-ion collision is proposed.
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  Shape Coexistence in Odd-Mass Nuclei near Z = 50

  CHENG XiaoLin, YANG LiMing

  理论物理通讯. 2000, 33(1): 93-98.

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  An earlier work dealing with shape coexistence for even-even nuclei is extended to treating odd-mass nuclei including proton excitations across closed shell. With the approach, energy spectra and some E2 transition branching ratios are calculated for odd-Anuclei^113~125Sb,^115~127I. The theoretical results give a good reproduction to the experimental data.
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  Constraints on Technicolor Models from Inclusive Decay of B Meson

  LU GongRu, HUANG JinShu, XIAO zhenJun, YUE ChongXing

  理论物理通讯. 2000, 33(1): 99-104.

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  Corrections to the branching ratio BR (B → X_s γ) from technipions and top pions appeared in technicolor models are investigated. We found that: (a) the multiscale walking technicolor model is ruled out since it is conflict with the CLEO data; (b) the topcolor-assisted technicolor model is consistent with the CLEO data of BR(B → X_s γ) for a certain range of parameters.
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  The Topological Quantization and Bifurcation of strings in Early Universe

  DUAN YiShi, JIANG Ying, YANG GuoHong

  理论物理通讯. 2000, 33(1): 105-112.

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  We present a new topological invariant to describe the spacetime defect in Riemann- Cartan manifold. By means of the φ-mapping theory and the rank-two topological tensor current (associated to the new topological invariant), we show that there must exist many string objects which naturally generated from the zero points of φ-mapping and is quantized in the topological level under the condition that the Jacobian J(φ/ν) ≠ 0. When J (φ/ν) = 0, we find that there exists a crucial case of branch process. Based on the implicit function theorem and the Taylor expansion, the origin and bifurcation of the strings are detailed in the neighborhoods of the limit points and bifurcation points of φ-mapping, respectively.
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  U_L(N) x U_R(N)-Invariant Four-Fermion Interactions and Nambu-Goldstone Mechanism at Finite Temperature

  ZHOU BangRong

  理论物理通讯. 2000, 33(1): 113-118.

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  In a chiral U_L(N) x U_R(N) fermion model of NJL-form, we prove that, if all the fermions are assumed to have equal masses and equal chemical potentials, then at the finite temperature T below the symmetry restoration temperature T_c, there will be N² massive scalar composite particles and N² massless pseudoscalar composite particles (Nambu-Goldstone bosons). This shows that the Goldstone theorem at finite temperature for spontaneous symmetry breaking U_L(N) x U_R(N) → U_L+R(N) is valid and consistent with the real-time formalism of thermal field theory in this model.
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  Study on the Radiative Decays of B Mesons in the Multiscale Walking Technicolor Model

  CAO YiGang, JIAO ZhengKuan

  理论物理通讯. 2000, 33(1): 119-124.

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  We calculate PGB (pseudo-Goldstone boson) corrections to the decays B → X_sγ and B → K^*γ in the MWTCM (multiscale walking technicolor model). The presence of PGBs in the MWTCM leads to large enhancements in the rates of B → X_sγ and B → K^*γ. But these results are in conflict with the recent CLEO data on the branching ratios BR (B → X_sγ) and BR(B → K^*γ). If topcolor is further introduced, the calculated results in the topcolor assisted MWTCM can be suppressed and be in agreemet with the CLEO data for a certain range of parameters. We also estimate the branching ratio BR (B → X_sg) in the topcolor assisted MWTCM, and this estimate is roughly one order higher than that in the standard model.
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  Mirror Instability with Electron Temperature Effects

  WU DeJin, CHAO JihKwin

  理论物理通讯. 2000, 33(1): 125-130.

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  Linear kinetic mirror instabilities of a homogeneous magnetized plasma in which both ions and electrons have the bi-Maxwellian distributions are investigated in the lowfrequency and long-wavelength limit. It is shown that, in contrast to the case of cold electrons, the criterion for the mirror instability has an upper limit, above which the mirror mode becomes oscillating one. This can possibly account for the oscillatory variations of observed mirror waves in the space plasma. In addition it is also shown that the growth rate of the nonpropagation mirror mode increases rapidly with the anisotropy parameter and is slightly higher than its value under the cold electron assumption, but that the oscillating mirror mode remains nearly a constant growth rate.
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  Improving Associative Memory Function in the Steepest Descending Asynchronous Network with Tunneling Rule

  GAO Mu, ZHANG ChengFu

  理论物理通讯. 2000, 33(1): 131-136.

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  In this paper effects of a new evolutionary rule added to the dynamics of the steepest descending asynchronous network model were studied. By numerical simulations, we found that the neural network operates very efficiently to improve the fault-tolerance when ,its capacity a ≤ 1 under the new rule. The simulations were conducted on both the low- and the highdimensional networks. A modified training scheme is also introduced.
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  An Exactly Solvable Model of Disordered System

  SHEN Yu, LU ZhangJi

  理论物理通讯. 2000, 33(1): 137-138.

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  An exactly solvable model of disordered system with infinite-ranged interaction is solved. We find that almost every eigenvector is localized.
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  The Duality Transformation for an n-Species Ising Model Interacting with Z₂ Gauge Fields on a Random Surface

  PAN ZhiGang, YE AiJun, CHEN Yuan, GUO ShuoHong, LI ZhiBing

  理论物理通讯. 2000, 33(1): 139-142.

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  The duality transformation is carried out for an n-species Ising spin system interacting with Z₂ gauge fields. For n > 1, we find that the dual model has topological terms when the surface is topologically nontrivial. The plaquette interaction of the gauge fields is dual to an n-spin coupling in the dual model.
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  A Realization of Yangian and Its Applications in Addition of Angular Momenta

  ZHAO ShuCheng, XIE BingHao, KANG XiangYang

  理论物理通讯. 2000, 33(1): 143-146.

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  A realization of Yangian associated with SL(2) has been constructed. Using its shift operators, we discuss Clebsch-Gordan coefficients and other applications in addition of angular momenta.
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  Analytic Representation of Traveling Wave Solution and Dispersive Relation in Tyson's Model

  ZHOU TianShou, ZHANG SuoChun, ZHENG ZuoHuan

  理论物理通讯. 2000, 33(1): 147-150.

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  The researches on traveling wave solution and dispersive relation in Tyson's model were only confined to numerical simulation and theoretically formal expression in the past, because of lack of the analytic representation of speed of the traveling wave. In this paper we give its analytic expression by Painlevé analysis, and so we can obtain the explicit representation of traveling wave solution and dispersive relation.
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  A Method of Determining Representation of Quonic Algebra

  YANG YaPing, LIN ZhiXin, FENG WeiGuo, WU Xiang

  理论物理通讯. 2000, 33(1): 151-152.

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  In this letter, we construct representation of quonic algebra in quite a different method compared with the conventional one.
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  Conditions for Collective Decoherence

  DUAN LuMing, GUO GuangCan

  理论物理通讯. 2000, 33(1): 153-156.

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  An efficient decoherence-reducing strategy exists if two qubits can be made decohered collectively. This paper serves to derive the explicit conditions for coJJective decoherence from a practical decoherence model. We describe two kinds of collective decoherence. In each case, a corresponding decoherence-reducing strategy is proposed.
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  Soliton Propagation near Zero-Dispersion Wavelength in Birefringence Fiber

  ZHONG WeiPing

  理论物理通讯. 2000, 33(1): 157-160.

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  fiom coupled nonlinear Schrodinger equation which describes the birefringence near zero-dispersion wavelength, we derive the evolution feature of soliton parameters and get the differential equation describing the evolution of interval between solitons along with propagation distance. At the same time, we have made detailed numerical research on the propagation in dissipation system of standard fundamental soliton. The result shows that for attractive potential, the distance of oscillation increases dong with the loss increases. For repulsive potential, the distance of oscillation diverges faster along with the loss increases. If selecting the proper-optical fiber of high-order dispersion, the interaction between solitons in birefringence fiber can be eliminated.