1990年, 第14卷, 第3期　
刊出日期：1990-10-30

  

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  Applications of the Stochastic Adiabatic Approximation

  WU Da-jin, CAO Li

  理论物理通讯. 1990, 14(3): 257-266.

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  In the previous paperi^[1], we have studied a class of nonlinear stochastic dynamical systems using the stochastic adiabatic approximation. A closed evolution equation for the slow variable u^t is obtained. In the present study, we use the methods proposed by the authors in Refs. [2] and [3] to treat the closed u^t equation which is derived by means of the new eliminating technique developed in Ref. [1] recently. Two important stochastic dynamical models, the simplified single-mode laser model and the stochastic Haken model, are treated concretely. The coupling effect of the additive and the multiplicative noise is found.
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  A Perturbation Theory of Zener Transitions in Dissipative Driven Systems

  Guang-ming ZHANG, Hong CHEN, Xiang WU

  理论物理通讯. 1990, 14(3): 267-274.

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  The effect of inelastic interactions on the Zener transitions in dissipative driven systems has been investgated by conventional perturbation theory in adiabatic approximation. Two canonical transformations are used to simplify the model Hamiltonian. In zeroth order approximation, we reproduce the previous results. Moreover, our theory can be used to calculate easily the higher order correction terms that would be difficult to obtain in the previous theory.
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  A Study on the Exciton-Ionized-Donor Complex Bound to the Surface of a Nonpolar Semiconductor

  GAO Er-zhen, GU Shi-wei, LI Bin

  理论物理通讯. 1990, 14(3): 275-281.

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  The exciton-ionized-donor complex with the donor on the surface of a semiconductor (X, D⁺)_s. is investigated for the first time. The binding energy of the complex is calculated variationally as a function of the effective mass ratio of the electron to the hole σ, and high-frequency dielectric constant ε_∞ of the host semiconductor occupying the semi-infinite space. The infinite potential barrier approximation, Levine wave function and the effective-mass approximation are used for the electron and the hole. The image potentials are also used to take into account the surface charge induced by the electron or the hole when it is near the surface. The results are presented graphically without any restrict of individual material. It is found that no unstable range of σ appears for (X, D⁺)_s.
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  A Chiral Quark Soliton Model for the Baryon Embedded in Nuclear Medium

  ZHANG Jian-wei, JIN Hong-li, QIU Xi-jun

  理论物理通讯. 1990, 14(3): 283-292.

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  A chiral quark soliton model for the baryon embedded in nuclear medium is proposed. The effective vacuum expectation value of the scalar field felt up by a quark of the baryon in nuclear medium is estimated. The model is solved for the hedgehog baryon state in the semiclassical approximation and self-conskitent approach. Some static properties of the baryon embedded in nuclear medium are calculated. An increment in ra&ns af the baryon is obtained. The numerical results can be used to explain the A-dependence of EMC effect and vacqum pressure constants in nuclear medium.
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  General Eight-Vertex Model and Braid Group Representation

  Mo-lin GE, Hong-kang ZHAO

  理论物理通讯. 1990, 14(3): 293-300.

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  The braid group representations (BGRs) corresponding to general eight-vertex model are obtained for the case in which the total spins are not conserved. A Yang-Baxterization scheme is applied to obtain from these BGRs.
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  The New Clue to Understanding fo(975) Meson From D_s Decays

  CHANG Chao-his, LI Xue-qian, WANG Jian-xiong

  理论物理通讯. 1990, 14(3): 301-310.

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  Based on the understanding of nonleptonic decays of charmed meson, the relative ratio Br(D_s⁺→f₀(975)π⁺/Br(D_s⁺→фπ⁺) is calculated. We argue that only (ss) component of f₀(975) contributes to it dominantly. The numerical result proves f₀(975) to be almost a pure (ss) state if the newly measured resultant value of the decay is trustable, and the conclusion is very usefulinformation as a clue for clarifying up the puzzle of 0⁺⁺ meson f₀(975).
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  Better Determination of α_s by Measuring Cross Section Differences in Hadronic Collisions

  Dong-sheng DU, Ma LUO

  理论物理通讯. 1990, 14(3): 311-324.

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  Three methods are proposed for the determination of α_s by measuring some special cross section differences in hadronic collisions. In these methods the calculated ratios α_s/a depend on neither gluon and sea quark distribution functions nor any other parton fragmentation functions. So using experimental data one can determine α_s more precisely in comparison with other methods of hadronic collisions.
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  The Geometrical Structure of Hamiltonian Systems with the Second Class Constraints

  ZHU Zhong-yuan, BAO De-hai

  理论物理通讯. 1990, 14(3): 325-332.

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  The geometrical structure of a classical Hamiltonian system with Dirac second class constraints is examined. It is shown that for the real physical sycltem, as the submanifold of the original manifold, we may redefine'the symplectic form and/or Hamiltonian vector fields to get consistent geometrical descriptions.
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  A Probable Origin and Radiation Mechanism for Gamma-Ray Bursts

  Shan-qun ZHAN, Tian-yi SHI

  理论物理通讯. 1990, 14(3): 333-344.

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  A model of the old and hot neutron stars (age γ～10⁸～10⁹ yr, temperature T_N～10⁷-10⁸ K) with the low magnetic field (B～10⁹-10¹⁰ Gauss) as the sources of Gamma-ray bursts is presented. In the range of medium energy (E < 400 KeV), the main radiation mechanism is still the thermal synchrotron radiation. The absorp tion features of the low frequency (E < 50 KeV) are resulted from the superposition of the blackbody spectrum emitted by the hot neutron star itself and the thermal synchrotron spectrum with self-absorption. And the spectrum for the high energy part (E > 400 KeV, including the emission features) is due to the annihilation emission from the unthermalized positrons and electrons. Using this model, we adopt the three component spectra to fit four representative spectra of Gamma-ray bursts. The results are satisfactory. Our model also avoids some difficulties existed in other modela.
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  The Propagation of the Nerve Impulse Under the Effect of a Magnetic Field

  J. Chela-Florea, E. M. El-Sayed, X. Y. WANG

  理论物理通讯. 1990, 14(3): 345-352.

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  The recent significant advance in ruperconductivity at high temperatures has raised an important problem in biophysics, in view of the underlying interest that haa arisen in experiments in which very high magnetic fields are needed (in the multi-teala range). This is occurring against a theoretical background in which there k no reliable way of estimating the effect of magnetic fields on the central nervous system. This has led us to discuss the problem of the coupling of magnetic fields with coherent propagation of the polarization of the plasma membrane along the axon. Our work lies within the context of the phenomenological model of nerve impulse popagation due to Hodgkin and Huxley. Using the concept of gauge invariance we find that the magnetic field has a non-negligible effect on the velocity of propagation of the action potential in the limit of the Fitxhugh-Nagumo equation without recovery, but more realistic cases do not change the main conclusions of this work.
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  Modes of Internal Motion of Three-Body Systems Containing a Lighter Particle

  DUAN Yi-wu, QIU Guo-chun, BAO Cheng-pang

  理论物理通讯. 1990, 14(3): 353-356.

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  Since the internal motion of few-body systems appears as a variation of the shape, the shape-densities are extracted from the eigensolutions of the 0⁺ states of a 3-body system containing a lighter particle. Detailed analysis on the shape-densities is made and a certain modes of internal motion are discovered.
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  Eigenstate Possessing ODLRO for Hubbard Model

  SONG Zhi

  理论物理通讯. 1990, 14(3): 357-358.

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  The Hubbard model is the simplest model expected to incorporate the essential feature of trong correlations. Since the discovery of high temperature suqerconductivity^[1], the Hubbard model has received renewed attention especially motivated by Anderson's^[2] suggestion that such phenomena in oxides can be understood already within this simplest model. In spite of the great amount of effort in solving this model, very few precise results are available, except in one dimension where many properties are accessible through the exact Bethe ansata solution. Recently, C.N. yang^[3] has constructed many eigdnfunctions of the simplest Hubbard model in three dimensions and these eigenfunctions possess off-diagonal-long-range-order (ODLRO).
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  Electromechanical Properties of Charge-Density-Wave Conductors:AC-DC Coupling Effects

  Sen LIU, Leigh Sneddon

  理论物理通讯. 1990, 14(3): 359-364.

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  We calculate perturbatively the Shapirc-Type anomalies in Young's modulus Y and internal friction δ of the CDW conductors when a combined ac and dc electric field presents within a classical model of two incommensurate, interacting, many-body eystem proposed by Sneddon. It is found that this model produces the experimental results very well at the weak pinning. Some experiments are suggested.
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  Sound of Speed in Nuclear Matter with Skyrme Forces

  LI Guo-qiang

  理论物理通讯. 1990, 14(3): 365-371.

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  An analytical expression for sound of speed in asymmetric nuclear matter is acquired, based on the thermal Fermi-gas model and Skyrme-type nucleon-nucleon interactions. A low temperature high density approximation is adopted to the Fermi-Dirac integrals. The dependence of sound of apeed on the temperature and density bf nuclear matter under consideration ie investigated. For all the cases concerned, the so-called superluminosity is observed, the position of which is found to depend on the force parameters used and the asymmetric parameter of the nuclear matter. A possible way to avoid this causal-constraint violation is suggested.
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  Cosmological Constraints on Weyl's Vector Meson

  Chao-guang HUANG, Han-qing ZHENG, Dan-di WU

  理论物理通讯. 1990, 14(3): 373-378.

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  We study the mass of Weyl'a vector meson (WVM) M_e in the model proposed by Hung Cheng. We find from cosmological constraints that M_e should be. either extremely light as no greater than 400 eV, or extremely heavy ae much greater than M_p, corresponding to the Weyl's gauge coupling constant f to be f < l0^-26 and f >> 1, respectively. We regard our results reasonable based on Dirac's large number theorem.
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  The Deconfinement Transition in SU(2) Lattice Gauge Theory:An Analytical Study

  J.M. YANG, L.D. WAN, C.M. WU

  理论物理通讯. 1990, 14(3): 379-382.

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  We study SU(2) lattice gauge theory at finite temperature in the variational cumulant expansion approach. The deconfinement transition is given in four and five dimensions. The comparison with Monte Carlo results ia also presented.