1999年, 第31卷, 第4期　
刊出日期：1999-06-15

  

• 全选
  |

• Select
  Pure Spinor Formalism for Conformal Fermion and Conserved Currents

  LIU YuFen, MA ZhongQi, HOU BoYuan

  理论物理通讯. 1999, 31(4): 481-490.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  Pure spinor formalism and non-integrable exponential factors are used for constructing the conformal-invariant wave equation and Lagrangian density for massive fermion. It is proved that canonical Dirac Lagrangian for massive fermion is invariant under induced projective conformal transformations.
• Select
  Ordered Structures of a Few Ions in the Paul Trap

  SHI Lei, ZHU XiWen, FENG Mang, FANG XiMing

  理论物理通讯. 1999, 31(4): 491-496.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  We have carried out a molecular dynamics stimulation for a few Paul-trapped ions exerted by a trapping force, inter-ion Coulomb forces and a damping force from a cooling source. The geometric structure in the ordered phase is studied in detail. It is found that the structure varies regularly with the ion number and forms concentric shells when the ion number grows. Furthermore, the similarity between the ions' structure and the potential of the trap is also presented. Finally, the case in the second stability region is investigated, which gives a comparison with that in the first stability region.
• Select
  The Features of Low-Lying States of Ne³, Ar³ and Kr³

  XIE WenFang, CHEN ChuanYu, LIU JunMin

  理论物理通讯. 1999, 31(4): 497-502.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  The methods for few-body physics are introduced to extract structures of low-lying states of threeatom clusters of neon, argon and krypton. Similarities among the states have been found, and accordingly a number of rotational bands have been identified. Each band is characterized by a specific mode of internal oscillation. The decisive effect of symmetry has been emphasized.
• Select
  The Conductance of a Mesoscopic Ring with a Quantum Dot

  YONG Yu, DONG JinMing, XING DingYu

  理论物理通讯. 1999, 31(4): 503-508.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  Employing the generalized Landauer-type formula and equations-of-motion technique, we present an analysis of the conductance for a mesoscopic ring with a quantum dot embedded in one of its arms. An explicit expression is obtained for the conductance of the device. The conductance, which is a function of single particle energy E' in the dot and the flux Φ through the ring, can be divided into three parts, G₁, G₂ and G₃. The second part G₂ is the most important term because it reflects the AB effect with a period of h/e. G₂ disappears in the vicinity of a conductance resonance of the system, which leads to a sudden phase shift by π. Moreover, under the condition of single-level approximation for the dot, we find that all resonances are in phase, which is in agreement with a recent experiment done by Yacoby et al. (Phys. Rev. Lett. 74 (1995) 4047).
• Select
  Theory of Photo-emission from the Two-Dimensional t-J Model on a Triangular Lattice

  DONG ZhanHai, FENG ShiPing

  理论物理通讯. 1999, 31(4): 509-512.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  The electron spectral function, the electron dispersion, and the electron density of states of the two-dimensional t-J model on a triangular lattice are studied within the selfconsistent fermion-spin mean-field theory. It is shown that there is a gap in the electron dispersions, and the global features of the electron spectral function is qualitatively similar to the result of the t-J model on a square lattice.
• Select
  Absence of Localization in One-Dimensional Lattice with Off-Diagonal Nonlinearity Disorder

  PAN ZhiWen, XIONG ShiJie, GONG ChangDe

  理论物理通讯. 1999, 31(4): 513-516.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  The time evolution of an initially localized mode in a one-dimensional lattice with off-diagonal nonlinearity disorder is studied by solving a modified nonlinear Schrodinger equation. Absence of localization is found when the nonlinearity parameter is beyond the selftrapping region for corresponding periodic httice. The propagation of electrons shows ballistic behavior even in the presence of disorder. When self-trapping occurs, the untrapped portion still escapes ballistically.
• Select
  Path Integral Method for Tunneling of Spin Systems and the Macroscopic Quantum Effect of Magnetization

  ZHANG YuBo, PU FuCho, LIANG JiuQing

  理论物理通讯. 1999, 31(4): 517-522.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  The quantum tunneling effect in a ferromagnetic particle which can be evaluated only for the ground state previously is extended to excited states within the framework of instanton method. The tunneling between n-th degenerate states of neighboring wells is dominated by a periodic pseudoparticle configuration with which a formula of level-splitting valid for entire energy region is derived. In low energy region periodic instanton results coincide exactly with those derived through the LSZ reduction procedure. The tunneling effect increases at excited states. These results should be useful in further investigation of phase transition problem in ferromagnetic particles.
• Select
  Solitons in the Two-Dimensional Antiferromagnetic Heisenberg Model

  LIU WuMing, YI JiDong, PU FuCho

  理论物理通讯. 1999, 31(4): 523-530.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  An effective Hamiltonian of the two-dimensional antiferromagnetic Heisenberg model is derived by using the Holstein-Primakoff transformation. Three nonlinear coupled partial equations of motion are obtained. In the long-wavelength approximation, these equations, are reduced to the envelope function equations by the method of multiple scales. The amplitude functions satisfy the nonlinear Schrodinger equation. Introducing an inverse scatteriag transformation, the single-, two- and multi-soliton solutions in the two-dimensional antiferromagnetic Heisenberg model are investigated.
• Select
  A Compensation Temperature Study of Bond-Diluted Mixed Ising Ferrimagnetic Spin System with Different Transverse Fields

  YAN ShiLei, YANG ChuanZhang

  理论物理通讯. 1999, 31(4): 531-536.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  The magnetic properties of bond-diluted nearest-neighbor interaction mixed spin-1/2 and spin-1 Ising ferrimagnetic spin system with different transverse fields are investigated within the framework of the finite cluster approximation (FCA). Particular emphasis is given to the square lattice with coordination number 2 = 4 for which magnetizations are obtained. The interactions Jij are assumed to be independent random variable with distribution P(J_ij) = pδ(J_ij-J) + (1-p)δ(J_ij), where J < 0. If bond concentration p varies in the certain ranges, we find that the compensation temperature is obtained for the values of the different transverse fields Ω_1/2 and Ω₁ in a restricted region. We obtain the values of the critical different transverse fields and critical bond concentration in this paper.
• Select
  A Quantum d-Dimensional Random-Field XY Ferromagnet

  MA YuQiang

  理论物理通讯. 1999, 31(4): 537-542.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  We propose a soluble quantum spherical XY ferromagnet with a random field in the boson space. We obtain a general expression of the critical temperat ure T_c below which the ordered ferromagnet phase appears. The Imry-Ma result concerning the lower critical dimension d_c = 4 is recovered, and the critical exponents near the critical temperature T_c are calculated. We show that the random-field fluctuations rather than the quantum fluctuations dominate the phase transition and critical behavior of the system. The entropy vanishes as T^d/2 at low temperatures, contrary to the classical spherical model.
• Select
  Cellular Model with Improved Decoupling Approximation in Random Nonlinear Composite

  XU Ping, LI ZhenYa

  理论物理通讯. 1999, 31(4): 543-548.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  Cellular model with improved decoupling approximation is proposed to study the effective nonlinear response in random nonlinear granular materials. The results are compared with numerical simulations on random nonlinear resistor networks, a good agreement is obtained.
• Select
  Crystal-Field Effect of spin-3/2 Transverse Ising Model

  YANG Rong, SONG WeiJi, YANG ChuanZhang, ZHU XiaoYan

  理论物理通讯. 1999, 31(4): 549-554.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  The crystal-field effect of spin-3/2 transverse Ising model is studied with the scheme of mean-field approximation. The influences of the crystal field and the transverse field on the phase diagram of the system are discussed.
• Select
  Decoding Information by Following Parameter Modulationin the Transmitter via Synchronization

  ZHOU ChangSong, CHEN TianLun

  理论物理通讯. 1999, 31(4): 555-560.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  This paper shows that the transmission of binary information using two different chaotic attractors in Chua's circuit for the two symbols ±1 of the information (Dedieu et al., IEEE Trans. Circuits Syst. 40(10) (1993) 634) can be decoded using a receiver which is a Chua's circuit subsystem driven by the transmitted signal bearing the information. The parameters of the receiver are adapted by the synchronization error of the receiver to the transmitted signal. Since the receiver follows the parameter modulations in the transmitter, the information can be read out by examining the evolution of the parameters of the receiver. It is shown by numerical simulations that the performance of the system is robust to parameter mismatches and external noise.
• Select
  Replica Symmetry Breaking in Critical Phenomena in Long-Range Disordered Ferromagnets

  WU XinTian, PAN ZhiWen, GONG ChangDe

  理论物理通讯. 1999, 31(4): 561-566.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  The replica symmetry breaking (RSB) is investigated in m-component ferromagnetic spin systems with a long-range disorder, with a correlation function obeying a power law ~s^-a. The Landau-Ginzburg Hamiltonjan with an RSB quartic interaction term is studied, with the renormalization-group expansion in ε = 4-D and δ = 4-a, where D is the spatial dimension. It is shown that the long-range disorder fixed point found previously is unstable under the perturbation of RSB for m<4 and stable for m≥4. The RSB fixed points are calculated and there is no physical stable fixed point for m<4.
• Select
  Effects of the Noise on Voltage-Current Characteristics of Josephson Effect

  CHEN Jun, CAO Li, WU DaJin

  理论物理通讯. 1999, 31(4): 567-572.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  In the case of T >> hω/k, by expanding the quasiparticle current power spectrum up to the third order term of hω/2kT, two noises are obtained: one is a white noise, the other is an O-U noise. We find that the two noises are the negative correlated noises, and correlation parameter λ is equal to -√6/3. Effects of the correlated noises on voltage-current characteristics curve are studied. The numerical computations show that the correlation parameter λ has very large effects on the voltage-current characteristics, but the correlation time τ of the O-U noise has a little effect.
• Select
  An Exact Interior Solution of a Static Charged Sphere in Higher Dimensional Spacetime

  ZHANG PengFei, ZHU DongPei

  理论物理通讯. 1999, 31(4): 573-576.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  By assuming "p = Aρ" and the total intrinsic energy density εr^k (k + D - 1 > 0), we strictly solve the higher dimensional Einstein-Maxwell field equations in a static charged sphere, resulting in an exact interior solution of the equations.
• Select
  W_∞ Algebra and High-Order Virasoro Algebra

  ZHAO WeiZhong, WANG Hong, ZHA ChaoZheng

  理论物理通讯. 1999, 31(4): 577-580.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  We give the relation between W_∞ algebra and high-order Virasoro algebra (HOVA), i.e., W_∞ algebra is the limit of HOVA. Then we give the super high-order Virasoro algebra from super W_∞ algebra.
• Select
  New Generalized Conditional Symmetry Reductions and Exact Solutions of the Nonlinear Diffusion-Convect ion-Reaction Equations

  QU ChangZheng

  理论物理通讯. 1999, 31(4): 581-588.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  The generalized conditional symmetry method, which is a generalization of the conditional symmetry method, is used to study the nonlinear diffusion-convection-reaction equations. In particular, power law and exponential diffusivities are examined and we derive mathematical forms of the convection and reaction terms which permit a new type of generalized conditional symmetry. Some new exact solutions of the governing equations can be obtained by solving the systems of two or three ordinary differential equations which arise from the compatibility of the generalized conditional symmetries and the governing equations.
• Select
  Enhanced K⁺/π⁺ Ratio from Central Collisions Between Heavy Nuclei at 1 GeV/Nucleon

  ZHENG YuMing, CHU ZiLi

  理论物理通讯. 1999, 31(4): 589-592.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  We generalized the previous relativistic Vlasov-Uehling-Uhlenbeck model to be able to identify the isospin degree of freedom of particles and used it to simulate the particle production in Au + Au collisions at 1 GeV/nucleon. The momentum spectra of proton, π⁺ and K⁺ particles, the multiplicities of π⁺ and K⁺, and the K⁺/π⁺ ratio as functions of the number of participating nucleons are studied. The theoretical results agree very well with experimental data. We also analyzed the physical origin of the significant rising of K⁺/π⁺ ratio when peripheral collision goes to central collision.
• Select
  Microscopic Description of g Factors and M1 Properties in Platinum Isotopes

  ZHANG ZhanJun, LIU Yong, SANG Jianping

  理论物理通讯. 1999, 31(4): 593-598.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  Starting from the shell model configurations, valence nucleon effective interactions and fermion M1 transition current density operator, the counterparts in the proton-neutron interacting boson model (sdIBM-2) of the fermion Hamiltonian and M1 transition current density operator are derived microscopically with the help of Dyson expansion technique. The boson g factors are abstracted from the boson M1 transition current density operator. Spectra, g factors of 2₁⁺, 2₂⁺, 4₁⁺ states and M1 matrix elements between 2₂⁺ and 2₁⁺ are calculated for the even ^192-198Pt isotopes in the sdIBM-2. The theoretical results fit experimental data quite well.
• Select
  Effect of Band Crossing Mode on the Variance of Moment of Inertia

  DI YaoMin

  理论物理通讯. 1999, 31(4): 599-606.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  In the frame of the Fermi dynamical symmetry model, the effect of band crossing modes on the variance of moment of inertia is discussed. It is shown that irrespective of the existence of I₁-band, it is the I₀-band crossing with the ground band that forms the first backbending. Without band crossing under the backbending, the heritage mixing itself can cause the variance of moment of inertia. The experimental data of well-deformed rare-earth nuclides can be well explained quantitatively with the model.
• Select
  Chaotic Motion of the cc System and a New Mechanism of J/Ø Suppression

  ZONG HongShi, GU JianZhong, LIU YUXIN, ZHANG XiaoFei, ZHAO EnGuang

  理论物理通讯. 1999, 31(4): 607-610.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  Based on random matrix theory and reduced BS equation, it is found that the regular motion of cc system can be expected at a small value of color screening mass but the chaotic motion at a large one. It is shown that the level mixing due to color screening serves as a new mechanism resulting in J/Ø suppression. Moreover, this kind of suppression can occur before the color screening mass reaches its critical value for J/Ø dissociation. In addition, it is. implied that a strong J/Ø suppression is possible in the absence of dissociation of J/Ø.
• Select
  Color-Triplet Pseudo-Goldstone Bosons and the HERA High-Q² Anomalies

  XIAO ZhenJun

  理论物理通讯. 1999, 31(4): 611-618.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  We estimate the cpntributions to HERA e^±p deep inelastic scattering process from the color-triplet pseudo-Goldstone bosons appeared in technicolor theory. We find that the F = 0 scalar technicolor leptoquark P₃', the lighter mixed state of charge 2/3 color-triplet pseudo-Goldstone bosons, can provide the required extra contributions to account for the excesses of both neutral and charged current events with very high Q² at HERA simultaneously.
• Select
  Solid-Effect Rate for Dynamic Nuclear Polarization of Spin-l/2 and Spin-1 Nuclei

  LIAO JiZhi

  理论物理通讯. 1999, 31(4): 619-624.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  The solid-effect rate equations for the dynamic nuclear polarization of spin-1/2 (tritium or hydrogen) or spin-1 (deuterium) nuclei are derived in the limiting case of the electronspin-resonance line width being much smaller than the nuclear-magnetic-resonance frequency. The exact analytical solutions of the rate equations for spin-1/2 nuclei are given, while the rate equations for spin-1 nuclei, which are nonlinear, are solved in decoupling approximation. The nuclear polarization and the electronic polarization as well as the times to polarization are calculated in low temperature limit. It is found that there is an optimal radio frequency pumping rate for the nuclear polarizations, which is not considered until now.
• Select
  Density Asymmetry and Marfe Localization in Tokamak Edge

  CHEN XiaoPing, SHI BingRen

  理论物理通讯. 1999, 31(4): 625-630.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  The effect of tokamak toroidal geometry on producing edge density and parallel flow asymmetries and its influence on Marfe localization are studied. In the presence of a large poloidal rotation, the density asymmetry is peaked at the high field side of tokamak edge and this becomes the seed of a condensation process, which triggers a Marfe there finally.
• Select
  Quantum Phase Transitions in Anisotropic Spin Ladders with Antiferromagnetic Rungs

  GU Qiang, SHEN JueLian

  理论物理通讯. 1999, 31(4): 631-634.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  We apply perturbation theory to study quantum phase transitions in anisotropic two-leg spin ladders with antiferromagnetic rungs in the strong interchain coupling limit. The energy gap is expanded up to the fourth order in the ratio of the intrachain to interchain couplings. The transition point is determined by examing the disappearance of the energy gap. Present results for the anisotropic ferromagnetic-leg spin ladder are consistent qualitatively with the nonlinear σ-model analysis and in good agreement with the numerical results by the diagonalization method.
• Select
  Number-Difference-Phase Uncertainty Relationship for Complex Scalar Fields

  FAN HongYi, CHEN ZengBing, FAN Yue

  理论物理通讯. 1999, 31(4): 635-636.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  For the complex scalar fields we introduce unitary phase operators which obey the definite number-difference-phase uncertainty relation. The behavior of phase operators can be demonstrated clearly in the common eigenvector representation of fields φ(x) and φ⁺(x).
• Select
  General Random Walk in One Dimension and Its Application to DNA Transcription Process

  MI Dong, SONG HeShan, HOU BoYuan

  理论物理通讯. 1999, 31(4): 637-640.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  We have derived a two-order difference equation about the general random walk in one dimension. Using this model in some physiological processes, we have calculated the average time in which enzyme released at random anywhere moves along a one-dimensional macromolecular strand to the end in quest of its binding site. From the results we can see that the average time can be affected greatly owing to the presence of "obstacles" on the macromolecular strand.