1986年, 第6卷, 第1期　
刊出日期：1986-07-30

  

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  STATISTICAL REPRESENTATIONS OF FOURTH ORDER TENSOR WITH D_∞h SYMMETRY ASSOCIATED WITH NEMATIC LIQUID CRYSTALS

  谢毓章, 欧阳钟灿

  理论物理通讯. 1986, 6(1): 1-15.

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  Accepting that a macroscopic physical quantity may be considered as the statistical average of the ccrresponding molecular physical quantity,we present in this paper the expressions of all the nonvanishing fourth order tensor xijkl with D_∞h symmetry associ-ated with nematic liquid crystals-in terms of the corresponding molecular fourth order tensors yijkl and the order parameters S₂ and S₄.
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  SOLUTIONS OF THE BOLTZMANN EQUATION FOR THE SPATIALLY HOMOGENEOUS MIXTURE OF MAXWELLIAN GASES

  吕燕南, 熊吟涛

  理论物理通讯. 1986, 6(1): 17-28.

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  Using the moment method,the general solution of the nonlinear Boltzmann equation for the spatially uniform binary mixture of Maxwellian gases for isotropic initial conditions is obtained in Laguerre series.Its general properties and asymptotic behaviors are investjgated.For the mixture with arbitrary parameters,a class of similarity solutions is derived.Two BKW solutions for the isotropic scattering model first found by Krook and Wu,are extended to including nonisotropic scattering models.
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  THE DIELECTRIC FUNCTION OF AN ELECTRON SYSTEM IN A PERIODIC STRUCTURE: VAA THEORY⁺

  薛登平, 卢德馨, 蔡建华

  理论物理通讯. 1986, 6(1): 29-37.

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  A general expression for the dielectric function of an electron system in a period structure has been derived by using linear response theory with the assumption that the equilibrium electronic density differs slight1y from its average value. Starting from the BBGKY equations,the theory is formulated in the Velocity Average Approximation.Numerical results for the dispersion and damping of plasmons and for the longitudinal dielectric function are given in the case of sinusoidally modulated structures.
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  THEORY OF THE P=2 LOCK-IN PHASE TRANSITION IN SURFACE RECONSTRUCTION

  胡根友

  理论物理通讯. 1986, 6(1): 39-47.

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  The p=2 lock-in phase transition in surface reconstruction is studied within the soliton picture by a two-dimensional lattice effective Hamiltonian,which has the coupling of the semiinfinite crystal.An analytical form of the p=2 soliton is obtained.Having complicated structure and narrowed width,the Soliton solution is found to be different from the ordinary form.This behavior is due to the coupled extra dis-tortion of the incommensurate phase in the surface reconstruction,and is necessary for the p=2 lock-in phase transition.The theory is consistent with many known experimental results and is applicable to other physical systems.
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  DN THE RENORMALIZABILITY OF FINITE TEMPERATURE FIELD THEORY

  虞跃, 汪容

  理论物理通讯. 1986, 6(1): 49-63.

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  We discuss the renormalizability of finite temperature field theory.A proof is given with inductive method that for any n-loop Feynman diagram,contributions originated from finite temperatures are always finite.Therefore a finite temperature field theory is.always renormalizable provided that the corresponding ordinary field.theory is renormalizable.
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  THE CURRENTS AND SOME NEW RESULTS IN THE SKYRME MODEL

  李炳安, 沈齐兴

  理论物理通讯. 1986, 6(1): 65-79.

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  In this paper,we obtain the expressions of electromagnetic current,charged current,baryon current and neutral weak current in the Skyrme model by means of the gauge transformations.A relation available for both cases of m_π=0 and m_π≠0 is given.The mean square radius < r² >_A of axial form factor is calculated and the result shpws that its value is much smaller than the experimental datum.In addition,the expressions of < r² >_M,T=l and < r² >_M,T=0 in our derivations are different from those given in Ref.[4] by a factor 3/5.
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  CONVECTIVE INSTABILITY OF A TWO-COMPONENT FLUID-FLUID SYSTEM

  陈燎原, 褚小麟

  理论物理通讯. 1986, 6(1): 81-93.

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  The stability of a plane interface of two immiscible liquids(both are finite thickness)with a perpendicular mass transfer is investigated by means of linear stability and energy methods.An analytical formula is derived for the linear stability boundary,whereas the numerical solutions are obtained for boundaries following from both linear and energy analyses. It is concluded that the difference in the chemical potential of.these two phases drives the convective flow and that a threshold Marangoni number existg for the instability to occur. It is also shown that the energy stability boundary does not coincide with that following from the linear analysis,so the subcritical instability is allowed in the region in between.