2001年, 第36卷, 第5期　
刊出日期：2001-11-15

  

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  Abundant Similarity Reductions and Dromion-Like Solutions to the Generalized Kroteweg-de Vries Equation in the (2+-1)-Dimensional Space

  YAN Zhen-Ya

  理论物理通讯. 2001, 36(5): 513-518.

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  In this paper,eight types of (1+1)-dimensional similarity reductions which contain variable coefficient equation,are obtained for the generalized KdV equation in (2+1)-dimensional space arising from the multidimensional isospectral flows associated with the second-order scalar operators by using the direct method.In addition,the cnoidal wave solution and dromion-like solution are also derived by using the reduced nonlinear ordinary differential equations.The (1+1) dromion obtained by Lou [J.Phys.A28 (1995) 7227] and Zhang [Chin.Phys.9 (2000) 1] is only a special case of our results.Moreover,some properties of the dromion-like solutions are analyzed.
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  Connes' Distance of One-Dimensional Lattices:General Cases

  DAI Jian, SONG Xing-Chang

  理论物理通讯. 2001, 36(5): 519-522.

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  Connes' distance formula is applied to endow linear metric to three 1D lattices of different topologies with a generalization of lattice Dirac operator written down by Dimakis et al.to contain a non-unitary link-variable.Geometric interpretation of this link-variable is lattice spacing and parallel transport.
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  Multisoliton Solutions of the (2+1)-Dimensional KdV Equation

  ZHANG Jie-Fang, HUANG Wen-Hua

  理论物理通讯. 2001, 36(5): 523-524.

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  Using the extension homogeneous balance method,we have obtained some new special types of soliton solutions of the (2+1)-dimensional KdV equation.Starting from the homogeneous balance method,one can obtain a nonlinear transformation to simple (2+1)-dimensional KdV equation into a linear partial differential equation and two bilinear partial differential equations.Usually,one can obtain only a kind of soliton-like solutions.In this letter,we find further some special types of the multisoliton solutions from the linear and bilinear partial differential equations.
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  Idealization Second Quantization of Composite Particles

  ZHOU Duan-Lu, YU Si-Xia, SUN Chang-Pu

  理论物理通讯. 2001, 36(5): 525-530.

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  A practical method is developed to deal with the second quantization of the many-body system containing the composite particles.In our treatment,the modes associated with composite particles are regarded approximately as independent ones compared with those of unbound particles.The field operators of the composite particles thus arise naturally in the second quantization Hamiltonian.To be emphasized,the second quantization Hamiltonian has the regular structures which correspond clearly to different physical processes.
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  A New Method for the Atomic Ground-State Energy in the Screened Coulomb Potential

  YU Peng-Peng, GUO Hua

  理论物理通讯. 2001, 36(5): 531-534.

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  The new method proposed recently by Friedberg,Lee and Zhao is applied to the derivation of the atomic ground-state energy with the inclusion of the screening effect.The present results are compared with those obtained in the pure Coulomb potential and by the variational approach.The overall good results are obtained with this new method.
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  Escape of Brownian Particles in the System Driven by Correlated White Noises:Comparison of Three Models

  YOU Jing-Yun, CAO Li, WU Da-Jin, ZHANG Li

  理论物理通讯. 2001, 36(5): 535-540.

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  The relative escape rate (RER) in the bistable sawtooth system driven by correlated white noises was studied in the case of linear multiplicative noise coefficient.And we compare the RER of linear multiplicative noise coefficient with the RER of the piecewise constant multiplicative noise coefficient in the bistable sawtooth system,finally compare the RER of the bistable sawtooth potential with the RER of the quartic potential in the case of linear multiplicative noise coefficient.It can be seen that the form of the multiplicative noise coefficient and the nonlinearity of potential have an important influence on the resonant activation and the suppression of the RER.The resonant activation of the RER vanishes in the negative correlation when the multiplicative noise coefficient was shifted from piecewise constant to linear function in the bistable sawtooth potential.The suppression of the RER disappears in the negative correlation when thelinear potential is converted into nonlinear one.
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  Lattice Green's Function for Infinite Square Lattice in the Second Nearest-Neighbour Interaction Approximation

  FAN Hong-Yi, LIN Jing-Xian

  理论物理通讯. 2001, 36(5): 541-546.

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  In dealing with the square lattice model,we replace the traditionally needed Born-Von Karmann periodic boundary condition with additional Hamiltonian terms to make up a ring lattice.In doing so,the lattice Green's function of an infinite square lattice in the second nearest-neighbour interaction approximation can be derived by means of the matrix Green's function method.It is shown that the density of states may change when the second nearest-neighbour interaction is turned on.
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  Simplified Scheme for Test of Quantum Nonlocality Without Using Bell Inequality

  ZHENG Shi-Biao

  理论物理通讯. 2001, 36(5): 547-549.

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  A simplified scheme is proposed for the test of quantum nonlocality of the type described by Hardy [Phys.Rev.Left.71 (1993) 1665] .In the scheme two appropriately prepared atoms are simultaneously sent through a cavity and dispersively interact with the cavity field.Then state-selective measurements are performed on these atoms,which may reveal quantum nonlocality without using Bell inequality.We also propose a simple scheme for the generation of multi-atom entangled states.
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  Obtain Lower-Dimensional Turbulence Systems from Higher-Dimensional Lax Integrable Models

  LOU Sen-Yue

  理论物理通讯. 2001, 36(5): 550-552.

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  Taking the well known (1-+l)-dimensional turbulence system,the Korteweg de-Vries Burgers equation,as a special example,we show that some types of lower-dimensional turbulence systems may be derived from some higherdimensional Lax integrable models,say,the (2+1)-dimensional asymmetric Nizhnik-Novikov-Veselov equation.On the other hand,using the Lax pair of the original higher-dimensional integrable model(s),we may obtain higher-dimensional Lax pair(s) for a lower-dimensional turbulence system.
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  Single Chargino Production with R-Parity Lepton Number Violation in Photon-Photon Collisions

  YIN Xi, MA Wen-Gan, WAN Lang-Hui, JIANG Yi, HAN Liang

  理论物理通讯. 2001, 36(5): 553-562.

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  We examine the process γγ→ x+ γ^- at photon-photon collider in the minimal supersymmetric standard model with R-parity violation,where all the one-loop diagrams are considered.We mainly discuss the effects of bilinear breaking terms,and conclude that their contributions may be important compared with trilinear terms.Our results show that the events of this process could be detectable at photon-photon colliders,if the values of the parameters are favorable.
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  A Critical Examination to the Unitarized IJ ＝ 20 ππ Scattering Chiral Amplitude

  ANG Qin, XIAO Zhi-Guang, ZHENG Han-Qing, SONG Xing-Chang

  理论物理通讯. 2001, 36(5): 563-568.

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  We discuss the Padé approximation to the ππ scattering amplitudes in one-loop chiral perturbation theory.The approximation restores unitarity and can reproduce the correct resonance poles,but the approximation violates crossing symmetry and produces spurious poles on the complex s plane and therefore plagues its predictions in some cases.However we find that one virtual state in the IJ = 20 channel may have physical relevance.
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  A Test of Color-Octet Heavy Quarkonium Production Mechanism

  DUAN Chun-Gui, YAN Zhan-Yuan, HE Zhen-Min

  理论物理通讯. 2001, 36(5): 569-572.

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  Using the scale evolution of nuclear parton distributions,the contribution of color-octet heavy quarkonium production mechanism to the P + Fe → J/ψ + γ + X process in calculated and discussed.Comparing our theoretical results with the future experimental data,the color-octet heavy quarkonium production mechanism can be examined.
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  A Phenomenological Analysis of Higher Fock State Contributions to the χ_CJ Decays

  HUANG Tao, WU Hui-Fang

  理论物理通讯. 2001, 36(5): 573-576.

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  We present a phenomenological analysis of higher Fock state contributions to the χ_CJ decays by using the recent BES experimental data.It is found that the higher Fock state |cc)8g〉 makes an important contribution to the inclusive and exclusive processes with respect to that from the valence Fock state |cc〉 of the χ_CJ and some constraints of these contributions are obtained for the χ_co and χ_c2 states in order to fit the experimental data.
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  Pomeron as a Reggeized Tensor Glueball

  MA Wei-Xing, A. W. Thomas, SHEN Peng-Nian, ZHOU Li-Juan

  理论物理通讯. 2001, 36(5): 577-582.

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  We study gluonic content of the pomeron and propose that the pomeron could be a reggeized tensor glueball ζ(2230) with quantum numbers I^GJ^Pc = 0⁺2⁺⁺.This conjecture is examined in high energy proton-proton elastic scattering,and the calculations lend a favorable support to our physical idea.
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  Extraction of Nuclear Matter Properties from Nuclear Masses by a Model of Equation of State

  K. C. Chung, C. S. Wang, A. J. Santiago

  理论物理通讯. 2001, 36(5): 583-588.

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  The extraction of nuclear matter properties from measured nuclear masses is investigated in the energy density functional formalism of nuclei.It is shown that the volume energy a1 and the nuclear incompressibility Ko depend essentially on μ_nN + μ_pZ - 2E_N,whereas the symmetry energy J and the density symmetry coefficient L as well as symmetry incompressibility Ks depend essentially on μ_n - μ_p,where μ_p ＝μp - ∂E_c/∂Z,μ_n and μ_p are the neutron and proton chemical potentials respectively,E_N the nuclear energy,and E_c the Coulomb energy.The obtained symmetry energy is J ＝ 28.5 MeV,while other coefficients are uncertain within ranges depending on the model of nuclear equation of state.
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  The Effect of Retardation on the Spontaneous Breaking of Chiral Symmetry in GCM

  YANG Sheng-Dong, ZHAI Chen-Yang, ZHOU Zhi-Ning, YANG Ze-Sen

  理论物理通讯. 2001, 36(5): 589-592.

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  An effective Hamiltonian including current-current coupling from the global color symmetry model is derived.Retardation effects are introduced by the factor (R/√π)e^-R2γ2 ,instead of δ(r) in the correlation kernel,from which the retardation gap equation with α-α coupling in the ³P_o vacuum is obtained,qq condensations of different retardation parameters R with or without the α-α term are calculated.The results show the effects of retardation,and indicate that the typical value of R is about 2 fm^-1 at reasonable value of qq condensation.And while taking typical value 1 fm^-1 of R,the condensation ^1/3 is about 13% larger than that with no retardation effect.With the α-αterms,the condensation ^1/3 is about 17% larger than that without it for all values of the parameter R.This shows that the retardation effects and the α-α terms are important for further studying in the Iow-energy region.
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  Effect of the Double Frequency of Trap Field in a Paul Trap

  NIE Zong-Xiu, FENG Mang, LI Jiao-Mei, SHI Lei, ZHU Xi-Wen, GAO Ke-Lin

  理论物理通讯. 2001, 36(5): 593-596.

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  The effect of double frequency oftrap field φ = U - V₁ cos Ωt - V₂ cos 2Ωt in a Paul trap can be described exactly by using a function series expansion to solve the corresponding Mathieu equation.The stability regions of a trapped ion are plotted and some meaningful physical results are shown.
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  Analytical Solution for an Ultracold Trapped Ion at the Node of the Standing Wave Laser Without Rotating Wave Approximation

  FANG Xi-Ming, FENG Mang

  理论物理通讯. 2001, 36(5): 597-600.

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  A method of solving an ultracold trapped ion at the node of the standing wave laser without rotating wave approximation is proposed and the analytical forms of the eigenfunctions and eigenenergies of the system are presented.
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  Energy Spectra,g Factors and Their Pressure-Induced and/or Thermal Shifts of SrTiO₃:Cr³⁺ and SrTiO₃:Mn⁴⁺ IV:R-Line Thermal Shifts of SrTiO₃:Cr³⁺

  MA Dong-Ping, ZHANG Ji-Ping

  理论物理通讯. 2001, 36(5): 601-610.

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  The local impurity-vibration modes (especially,the Iow-frequency one) of SrTiO₃ :Cr³⁺ cause a very large R-line blue-shift;while the Raman term,neighbor-level term and optical-branch term relevant to the lattice vibration cause smallred shifts.The algebraic sum of them gives rise to the observed unusual and large R-line thermal shift (blue-shift) of SrTiO₃:Cr³⁺.By taking into account all the irreducible representations and their components in the electron-phonon interaction (BPI) as well as all the levels and the admixtures of basic wavefunctions within d3 electronic configuration,the values of the parameters in the expressions of thermal shift (TS) from EPI for the ground level,R level and R line of SrTiO₃:Cr³⁺ have been evaluated;the R-line TS and various contributions to it have been calculated in two temperature ranges (30 K ≤ T ≤ 80 K and 130 K ≤ T ≤ 300 K).The contribution to R-line TS from thermal expansion has been approximately neglected in this work.Furthermore,the improvement on simplified approximation of adopting a single low-frequency impurity-mode and neglecting its hardening in Iow-temperature region has been made.
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  Short-Time Dynamics of the Random n-Vector Model

  CHEN Yuan, LI Zhi-Bing, FANG Hai, HE Shun-Shan, SITU Shu-Ping

  理论物理通讯. 2001, 36(5): 611-616.

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  Short-time critical behavior of the random n-vector model is studied by the theoretic renormalization-group approach.Asymptotic scaling laws are studied in a frame of the expansion in ε = 4 - d for n ≠ 1 and √ε for n = 1respectively.In d ＜ 4,the initial slip exponents θ′ for the order parameter and θ for the response function are calculated up to the second order in ε ＝ 4 - d for n ≠ 1 and √ε for n ＝ 1 at the random fixed point respectively.Our results show that the random impurities exert a strong influence on the short-time dynamics for d ＜ 4 and n ＜ n_c.
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  Anomalous Dimension in the Solution of a Nonlinear Diffusion Equation

  TU Tao, CHENG Geng, LIU Jian-Wei

  理论物理通讯. 2001, 36(5): 617-619.

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  A new method is used to obtain the anomalous dimension in the solution of the nonlinear diffusion equation.The result is the same as that in the renormalization group (RG) approach.It gives us an insight into the anomalous dimension in the solution of the nonlinear diffusion equation in the RG approach.Based on this discussion,we can see anomalous dimension appears naturally in this system.
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  The Physical Property of Susceptibility for One-Dimensional Ferrimagnetic Chain with Alternating Spins 1 and 1/2 in Finite Magnetic Field

  XIE Gang, HAN Ru-Shan

  理论物理通讯. 2001, 36(5): 620-622.

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  We further calculate the dependence of χT on T in high magnetic fields,where χ denotes susceptibility and T is temperature,using our previous research work - Green function's decoupling approximate approach,for the one-dimensional ferrimagnetic chain with alternating spins 1 and 1/2.We find a linear correlation in certain range of magnetic field between the temperature of χT maximum and the magnetic field.Moreover,we simply analyze its physical meaning by our approach.
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  Spinless Excitons Implicit in SO(5) Theory

  JIANG Yong-Jin, TAO Rui-Bao

  理论物理通讯. 2001, 36(5): 623-624.

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  A pair of up-down operators are constructed explicitly for S.C.Zhang's SO(5) theory of high T_c superconductivity.From them two good quantum numbers are derived.The up-down operators are related to the spin-independent excitons which are not considered before.
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  A Monte Carlo Study of the Half-Filled Two-Dimensional Hubbard Model

  ZHU Xing, LIU Chuan

  理论物理通讯. 2001, 36(5): 625-630.

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  Using the path integral representation,bulk thermodynamic properties of the two-dimensional Hubbard model on a square lattice are studied numerically using the hybrid Monte Carlo simulation algorithm.Results for averaged energy,spin-spin correlation functions and Cooper pair correlation functions are presented.All these results suggest that the system exhibits an anti-ferromagnetic correlation at half-filling for a wide range of temperature.
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  Binding Energy of an Exciton Bound to Ionized Acceptor in Quantum Dots

  XIE Wen-Fang

  理论物理通讯. 2001, 36(5): 631-634.

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  Binding energiesfor an exciton (X) trapped in the two-dimensional quantum dot by a negative ion located on the z axis at a distance from the dot plane are calculated by using the method of few-body physics.This configuration is called a barrier (A^-,X) center.The dependence of the binding energy of the ground state of the barrier (A^-,X)center on the electron-to-hole mass ratio for a few values of the distance d between the fixed negative ion on the z axis and the dot plane is obtained.We find that when d → 0,the barrier (A^-,X) center has not any bound state.We also studied the stability and binding energy of the ground state of the barrier (A^-,X) center in a parabolic quantum dot as a function of the distance d between the fixed negative ion on the z axis and the dot plane.
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  Memory,Time and Technique Aspects of Density Matrix Renormalization Group Method

  QIN Shao-Jin, LOU Ji-Zhong

  理论物理通讯. 2001, 36(5): 635-640.

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  We present the memory size,computational time,and technique aspects of density matrix renormalization group (DMRG) algorithm.We show how to estimate the memory size and computational time before starting a large scale DMRG calculation.We propose an implementation of the Hamiltonian wavefunction multiplication and a wavefunction initialization in DMRG with block matrix data structure.One-dimensional Heisenberg model is used to illustrate our study.