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.

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.

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.

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.

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.

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.

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.

In this paper we show analyticaliy that,in general,nematic liquid crystals (NLC) with curvature strain belong to the C₁[1] point group.However,NLC with simple splay deformation or simple bend deformation possess C_2V[mm2] symmetry and those with simple twist deformation possess D₂[222] symnetry.

We first used Bethe lattice method and coherent potential approximation method to calculate the densities of bulk and surface states for a-Si,a-Si:H. The ideal vacancies were also studied.The results agree with experiments and other works.Dihedral disorder contributes to the submerging of a peak and sp peak of the valence band.In hydrogenated case,extra structure appears in the spectrum of densities of surface states.Doped hydrogen affects the densities of bulk states in the gap in principle,but hydrogen is not important for densities of surface states in the gap.Finally,we obtained self-energies which are in good.agreement with the empirical results from experiments and other methods^[1].

To include not only the perturbative effects but also the nonperturbative effects, the bac.ground field method is used in the OPE of two-point correlation function. The sum rules for the "lnonrents" of pion distribution amplitude are obtalned by using this method. We find that the values of "moments" are much larger than their perturbative values at intermediate Q². This result Indicates that the behavior of pion distribution amplitude is much broader than its asymptotic behavior at intermediate Q².

The scattering of quark u to antiquark u^C on the SU(5) colorless magnetic monopole is discussed in some detail.The baryon number non-conserved processes occur to the state j=1/2 and j=3/2 of the third type solutions. Solving the radial equation with j=1/2 and j=3/2 numerically,we show that the plane wave of quark u with helicity-1 can be scattered by the colorless monopole into antiquark u^C with the cross section σ=2π/p2.

The B?cklund Transformation presented by Chau et al. is reproduced as a self-consistent regular Riemann-Hilbert transform, so that it might correspond to a kind of non-solitonic transformation.

In this paper, a Λ-N potential is presented. The long and medium range parts of this potential are given by the OBEP(κ+η+ω+η+Φ) and TBEP(2π+πp),while the short range part by a phenomenological soft core. Based on the Λ-N potential, the Λ-separation energies and the spectra of ?He and ?H as well as the s-wave phase shifts and the cross section of the Λ-N elastic scattering are calculated.The results are in good agreement :with the experimental data. Finally, the Λ-well depth innuclear matter is discussed.

It is shown that in the pion induced double charge exchange reaction on J^p=O⁺→O⁺ nuclei,there exists a possible new reaction mechanism π⁺(Δ⁰,Δ⁺⁺)π^- or π⁺(Δ^-,Δ⁺)π^- in so-called single step process,while that old speculative mechanism π⁺(N,Δ)π^- or π⁺(N,Δ)π^- is firbidden by a well-known selection rule which has been indicated in the theory of the nuclear 2β-decay.

We present results of a hydrodynamic study of the plagmon spectra in metallic superlattices by treating the different layeqs as jelliums.Interesting changes in the plasmon dispersions and relative growth and decline of the bulk and interface modes with modulatiqn wavelength and transversal wave vector are noted. A variation of the electronic effective mass with the modularion wavelength has also been found.

Using the Dual Partonic Model and combining with the FF quark fragmentation mechanism,the charged particle multiplicity in the central region are simulated by Monte-Carlo method.The variation of the charged particle multiplicity with total C.M. energy and the charged particle multiplicity distribution in central region as well as the sinqle-particle inclusive distribution are evaluated.The calculated values are in good agreement with recent experimental data.The results support the view point that the reexist colliding components in soft-collisions.

The microscopic calculations of the effective nuclear interactions in the Landav Fermi-Liquid theory were performed in the framework of both the nonrelativistic Brueckner theory and rela-tivistic mean-field theory. The Landau parameters obtained from the relativistic approach exhibit a strong density dependence.In the vicinity of the nuclear saturation density the strong density dependence of the scalar and isoscalar Landau parameter F₀ has somewhat eased up by the many-body force of nucleons.

The positron spectra produced by very heavy ion collisions have been measured in GSI. The fluctuation phenomena occured in the positron spectra should be explained in terms of the theory on the interference effects between atomic and nuclear processes, i.e. the origin of this kind of fluctuation essentially comes from the stochastic property of compound ,nucleus.This paper shows the theoretical framework.

A linear stability analysis for a two-component Benard liquid with surface adsorption has revealed a dual role for the surface tension arising from the surfactant-it plays a stabilizing role in some cases and a destabilizing role in others.We have introduced a dimensionless parameter-surface excess number,proportional to the concentration gradient of solute and inversely proportional to the surface adsorption accumulation,to describe the dual effects of surface tension.We predict the existance of a critical surface excess number and calculate its value for two different boundary conditions.Our results have solved the seeming1y contrary results obtahed by Berg and Palmer and Velarde.

Null geodesics in equatorial plane of stationary Ernst-Wild space-time representing a Kerr black hole immersed in axlsymmetric magnetic field are investigated.As the case of static Ernst space-time there are two types of geodesics which depend on a dimensionless parameter β of the magnetic field.Differing from the static Ernst space-time,however,the critical β_C now depends on a dimensionless parameter q of the angular momentum of the Kerr black hole,and the relation between β_C and q is qualitatively different in two cases:L>O and L<0 where L is a dimensionless parameter of angular momentum of test particles moving along nu11 geodesics.

In terms of the technique of perfoming integra-tion within ordered product we show the integra-tion appearing in the rotation operator ∫d³r^→|Rr^→ >< r^→|≡D(R) can be explicitly carried out and leads to a kind of new operator identities,their coherent state matrix elements are then easy to be computed.

The average plaquette energy < E_p > of U(1) lattice gauge theory in d=3,4 and 5 dimensions is calculated by curnulant expansion.In each case the results are in agreement with those of Monte Carlo data^[1,2,3].

A simple Interacting Boson Model Hamiltonian involving only Q.Q and L.L terms is used to describe the Inversion of the β- and γ- bands in the rare earths. The model is used to describe this band inversion in the Hafnium isotopes.An inttrpreta-tion of this simple Hamiltonian in terms of the dynamical groups U(5),SU(3) and O(6) is presented.

We present a generalization of thermodynamic perturbation theory to the intermediate valence systems with two magnetic configurations.

Including the inertial term and using the singular perturbation method, we solved analy tically the eqtiation of motion for the CDW system βφ+φ-sinφ=e₀+e₁ cosωt in the classical particle model under approximation β << 1 and e₁ << L. The existence of the subharmonic steps has thus been directly demonstrated in good agreement with the experiments on the CDW system.

We study in this paper the effects of lattice quantum fluctuations upon the order parametert in the Peierls systems by using the Green's function technique.We start from the discrete Su-Schrief fer-Heeger model with quantized phonon field and derive a coupled system of equations for the order parameter and Green's functions.It turns out that the order parameter is reduced compared with the adiabatic value but the Peierls instability survives the quantum fluctuations in agreement with,Monte Carlo results.The band-to-band optical absorption coefficient of polyacetylene with lattice fluctuation being accounted for is also calculated and compared with the experimental data.

An extensive Smoluchowski equation with neutron emission is suggested in this paper and is analytically solved by means of van Kampen technique.The average fission rate,fission probability,the ratio of neutron emission to fission are calculated for composite nucleus ²⁴⁰PU. The time evolution of these quantities is analysed and their essential dependence on fission potential height and nuclear temperature are discussed.A fair1y substantial particle evaporation prior to fission in heavy-ion reactions can be well understood in our diffusion model.

Taking three Euler angles as the field variables of nonlinear σ model of SU(2),we calculated the Wess-Zumino term and showed by using canonical quantization that the chiral cuirents of this model satisfy a Kac-Moody alqebra at n equal an even intsger for arbitrary value of λ^o.

A formula is provided to check the correla-tion of pulsars and supernova remnants,using only observable pulsar parameters.The validity of this formula depends on the assumption that the value of the initial pulsar frequency is much greater than the present value.A test for this assumption is suggested.

In this paper,we derive a boson-fermion hybrid representation for the antisymmetrizer,and obtain an exact mapping of the fermion space onto a hybrid space.The results show that the effect of the antisymmetrizer appears as different kinds of many body forces among the bosons and the fermion.

The equation of state and the isothermal line for the two-dimensional alternative binary system are discussed in this paper. We found the regularity of variance of the critical state with the composition of binary system, and obtained the linear relationship between the critical pressure and the critical temperature. We showed that the value of the critical coefficient is independent of the composition and coincides with the experimental data for the three-dimensional substances in quantitative 1eve1 .

The gyrokinetic quaailinear equations for an axisymetric geometry are derived including parallel current.A possible application to the generation of currents in a tokamak by lower hybrid waves is discussed.

In terms of the properties of both the Glauber coherent state and normal product,we derive a kind of new representation-notmal product representation for the SU,group.