In a phenomenological two-level model, by using Floquet method, we directly calculate the multiphoton transition probability between the Rydberg states of an alkali-metal atom in strong microwave fields. The convergence of the truncated Floquet matrix, and the influences of parameters upon the multiphoton resonant spectra are discussed. The results show that our method can give clearer physical picture and better results about the multiphoton transition than indirect methods. Moreover, our method can easily be generalized to treat multi-level models.

From the potential model of Lennard-Jones (12-6) and equilibrium separation TO of the intermolecular force, one can give small nonpolar molecule rational and classical estimate of the effective ranges of repulsive intermolecular force γ_λ and the effective ranges of attractive intermolecular force γ_μ with semiempirical formulae: T_λ = 2γ₀, γ_μ = 3γ_λ = 6γ₀. he γ₀ can be sketchily calculated with molar mass and density of the liquid state ρ₁. In this article, we give the values of γ₀,T_λ and γ_λ of seventeen kinds of small nonpolar molecules. As a general rough result, the approximate values are γ₀ = 0.4 nm, T_λ = 0.8 nm, γ_λ = 2.4 nm.

In discussion about the detection of the BoseEinstein condensation, the adiabatic approximation method was taken. According to the perturbation theory, this approximation is studied in detail by a single atom model in this paper.

The Hardy's theorem [Phys. Rev. Lett. 71 (1993) 1665] is extended to n spin-s particles. As expected, the entangled states for these particles also admit a proof of nonlocality without using inequalities.

A Green function formalism is employed to investigate the effect of magnetocrystalline anisotropy on surface spin waves in semi-infinite Heisenberg ferromagnets at low temperatures T << T_c. The dispersion relations are investigated in detail. The density of states (DOS) of surface spin waves and layered magnetizations are also derived.

We describe the molecular ferromagnet decamethylchromocenium tetracyanoethanide [C_rC_p2^*] [TCNE] by a quasi-one-dimensional alternating-spin model with ferromagnetic exchange interaction. The spin-wave theory is used to discuss the magnetic excitation of the molecular ferromagnet. We obtain the magnetizations corresponding to different external magnetic fields without interchain exchange interaction which is consistent with the experimental results. The formula of the Curie temperature T_c is obtained by using the thermodynamic Green's function method. It is found to be related to the spin of donors, to the intrachain exchange interaction and to the spatial anisotropic parameter. The result obtained by this T_c formula is consistent with the experimental result T_c = 3.6 K for [C_rC_p2^*][TCNE].

The effective Hamiltonian and the renormalized mass of surface polaron, where the electron is strongly coupled with the surface optical (SO) phonons but weakly or intermediately coupled with the bulk longit udinal-optical (LO) phonons, were first reviewed. The self-energy and the renormalized mass of the polaron for the polar crystals of potassium iodide, silver chloride and silver bromide are evaluated as a function of the depth Gom the crystal surface. Results of our calculation indicate that the effect of the electron-SO phonon interaction is dominant only within a very small layer from the crystal surface. Its justification awaits further experimental results.

The problem of Kondo effect in a Luttinger liquid which consists of right-moving, spin-up electrons and left-moving, spin-down electrons is investigated in the bosonized form, and the phase diagram at zero temperature is obtained by a yavefunctional method.

In this paper, unified colored noise approximation is extended to treat the systems driven by Poisson colored noise χ = ν(χ) + gε_cp(t). We arrive the evolution equation of the probability distribution pi(x, r) and the stationary probability distribution pt (χ, Υ). These equations are valid only if γ(χ,Υ) ≡ γ^-1/2[1 - ΥG(χ)/g(χ)] (G(χ) ≡ v'(χ)g(χ) - v(g)g'(χ)) is large enough (positive) and t >> Υ/γ(χ, Υ), but Υ is not restricted. As an application, we derive the nonlinear relaxation time (NLRT) for the processes driven by Poisson colored noise and evduate the NLRT for the approximative Ginzburg-Landon model under small Υ.

We focus on the discontinuity of a neural network model with diluted and clipped synaptic connections (±l only). The exact evolution rule of the average firing rate becomes a discontinuous piece-wise nonlinear map when very simple functions of dynamical threshold are introduced into the network. Complex dynamics is observed.

An earlier work dealing with low-lying collective states in nuclei is revised and improved. Correlated and independent nucleon S and D pairs properly modified so that they behave approximately like bosons are constructed in terms of which a model space for lowlying collective states is defined, and a microscopic basis for IBM is thus set up. All dynamical variables can also be "bosonized", i.e., expressed in terms of these "bosons" but with statedependent coefficients or operators to incorporate their state dependence in model space.

The effects of two kinds of coherent lengths, the wave packet length of the emitter and the radius of the coherent source, on pion spectrum distribution are studied. It is shown that both coherent lengths can cause abundant pions at low momentum. Observing abundant pions at low momentum may be taken as a signal of DCC effects.

The extended χ-rescaling model has previously shown to give a good description of the EMC effect. Here, we extend the model to describe the gluon distribution of nucleons bound in nuclei by combining with the nuclear shadowing effect due to the spatial overlap of gluons from neighbouring nucleons in the nucleus in small χ region. The calculated result for G_sn(χ)/G_C(χ) is in good agreement with the experimental data of the New Muon Collaboration (NMC).

On the basis of the phase formulation, we find the quantum and classical exact solutions and corresponding total phases for the Klein-Gordon (KG) field with a time-dependent Hamiltonian. The total phase includes both the dynamical and geometric phases (Abaronov-Anandan phase). The connection between the quantum and classical solutions is then obtained. From this connection, we discuss the condition under which the geometric phase for the KG field can be defined.

In this paper, we carefully analyze the unitarity of the simplest Kazama-Suzuki model based on the noncompact group. The chiral ring structure in this N = 2 theory is clarified. In general, it is infinitely dimensional and innumerable. The primary chiral states belonging to the ring can be constructed by means of the direct products of the highest weight states of the coset SU(1,1)/ U(1) and the scalar representation of U(1) for the fermions. The primary chird and anti-chiral states Jive individually in the positive discrete series D⁺ and negative discrete series D^- of SU(1,1), respectively. With appropriate restrictions, this theory can be regarded as one at the fixed point of a Landau-Ginzburg theory, in which the superpotential is given by S₁₂ in the fourteen exceptional singularities.

For the cb system, the mass spectra, decay constants, El and M1 transition rates are calculated in a QCD-inspired potential model. Relativistic corrections are taken into account. The El transition rates with relativistic corrections are found to be smaller than those obtained in other models.

A static soliton solution is obtained from the field equations of chromodynamics. The relativistic wave equation for meson states in which the quark and antiquark interact through the intermediary of this gluon field gives rise. to the same wavefunction and mass spectra obtained before under the independent particle approximation. The calculated values of mass difference of η_c and Ψ/J particles and mass difference of Ψ(3685) and Ψ(3770) due to spin-dependent part of the interaction are in good agreement with the experiment.

The dimensional regularization is applied to three-loop vacuum graphs in massless QED to evaluate temperature-dependent ultraviolet divergences and infrared divergences in arbitrary covariant gauge. They both are shown to be absent due to cancellations among themselves, and the cancellations are gauge-independent although the individual divergences are gauge-dependent.

A specific texture for the Dirac and Majorana mass matrices in the seesaw model leading to a pair of almost degenerate neutrinos is discussed. This texture can be obtained by imposing a global U(1) symmetry. This model could solve the solar neutrino problem through the MSW mechanism and offer the hot component of the dark matter of the universe which requires Σm_vi = 7 eV.

A theory of the carrier thermal conductivity for electron antiferromagnetic spin fluctuation scattering has been developed and on this basis the experimental results of high-T_c oxides have been interpreted. Our theoretical analysis fits the experimental results excellently and suggests that the antiferromagnetic spin fluctuations affect the carrier thermal conductivity in high-T_c oxides.

A quantum version of the site-random Heisenberg planar XY model in a random field is presented in the boson representation. Like classical spherical model in the spin space, the model can be solved exactly within the coherent state path integral-representation. The phase diagram is obtained, and the effects of the randomness and quantum fluctuations on the onset of a spin glass phase are discussed.

We show that the newly found complete and orthonormal representation <λ|, which is constructed in terms of guiding centers and canonical momenta of an electron moving in a uniform magnetic field, also helps us to establish a systematic phase operator theory. The unitary phase operator, interpreted as a quantity canonically conjugated to the electron angular momentum, manifestly exhibits in the <λ| representation its phase behavior. As a byproduct, the phase distribution function, in the correct sense of probability in quantum mechanics, can also be defined by the <λ| representation.

The critical exponents of the triangular lattice Ising model with long-range interactions γ^-s are calculated by the real space renormalization group. Using the simplest Kadanoff blocks and the lowest approximation of cumulant expansion, it is shown that there exists a finite critical temperature when 4(1 - ㏑2/㏑3) < s < 4.

The q, s-Zhyhr's formula with its q, s-remainder by using the q, s-djfferentiation approach is given.

After introducing briefly the basic concept of statistical interaction, we illustrate it on integrable XXZ chain corresponding Potts case by the Bethe ansatz and point out that the nontrivial part of this statistical interaction comes from the rates of change of phase shifts with respect to momentum.

It is proved that subject to certain physically reasonable restrictions on the curvature of spacetime, an algebraically special, asymptotically simple and empty spacetime is necessarily a copy of the Minkowski space. This imposes further requirements a nontrivial asymptotically simple and empty spacetime has to satisfy.

Because of the arbitrary property of the singular manifold, the usual singularity analysis can be extended to a different form. Using a nonstandard truncation approach, five special types of exact solution of the coupled nonlinear scalar field equations are obtained.

Based on the relationship between electron deep inelastic scattering and forward virtual photon Compton scattering, and using the information provided by virtual photon absorption on target, we study spin-dependent structure function of deuteron and its correspondingfirst moment, which are expressed by total absorption cross sections of virtual photon. The absorption cross section is determined by helicity amplitudes A_1/2 and A_3/2 which are evaluated in SU(6) quark model with an improved electromagnetic interaction. The method avoids the difficulty for solving nonperturbative QCD which is impossible at present. In general, our theoretical predictions on the first moment and quark polarization in deuteron are in good agreement with data of El43 at SLAC, EMC at CERN and Hermes at DESY.

A quantum dynamical R-matrix (QDRM) with three distinct eigenvalues, which is a trigonometric solution of the Germis-Neven-Felder equation, is constructed from the fusion of the simplest 4 × 4 trigonometric QDRM of Hecke type for sl(2).

In this paper, we study quantum statistical properties of atoms and photons in interaction of ⁷Li-atornic Bose-Einstein condensate in the ground-state hyperfine sublevels with laser fields. We investigate not only quantum conversions between atoms in the condensate and photons in the quantized laser field, but also transfer of nonclassical cha acteristics of atoms and photons between input states and output states when the atom field is initially in a number state and the quantized laser field is in the even coherent state and the odd coherent state, respectively. We find various conditions to realize these quantum conversions. We also study atom-photon quantum correlations and their input-output conversions. It is indicated that there are atom-field nonclassical correlations.

In coherent-state representation, the Jaynes-Cummings (JC) model in the absence of rotating wave approximation (RWA), i.e., in detuning case, is treated by the solution of some differential equations with constant coefficients and can be exactly solved. This approach can be easily extended to deal with the JC model without RWA in more complicated cases.

Influences of the Aharonov-Bohm flux on the improved soliton in a one-dimensional ferromagnetic ring are considered. The results show that the width, the peak, the rest energy and the effective mass of the improved soliton are dependent upon the Aharonov-Bohm flux and influences of the Aharonov-Bohm flux on the improved soliton are greater than those on the usual soliton.

Features of the low-lying states of a three-electron quantum dot under a very strong confinement are investigated by few-body methods. We find that the energy spectra are changed greatly compared with the energy spectra under a weak confinement; and the mechanism producing the magic numbers remains working just as in the case of a weak confinement. Furthermore, the degeneracy law of the energy spectra of the low-lying states and the platform effect of the degeneracy degree in close connection with the uncontinuous change of some macroscopic physical properties of materials are discovered for the first time.

In this paper a method is developed which directs trajectories to a target by using meso-targets. The method can rapidly direct orbits from an arbitrary initial state to a target by making small perturbation of available system parameters. It is simple, efficient and reliable. Numerical experiments are given in Hhnon map.

For the independent-oscillator model (IOM), the explicit expressions of the instantaneously dynamical response functions (Χ₁ + Υ,t₁), X(t₁ + Υ,t₁)) and correlation functions (φ(t₁ + Υ,t₁)+Φ(t₁ + Υ,t₁)) for both the system and environment are derived. It is shown that for external perturbation the environment of IOM is dynamically stable and the system is oscillatory. Although the external perturbation exists, there is still strongly temporal correlation for the system, for the environment, however, the temporal correlation quickly decays with the second time variable Υ and is almost independent of the first time variable t₁, nevertheless is significantly affected by dissipation. It is shown that the environment behaves as a heat bath from the dynamical point of view.

A general method used to calculate the time-dependent probability distribution from the switching time distribution ψ(t, a) and the transition probability ρ(a, b) for Markovian noises is presented, and the way how to describe the noises treated as diffusion processes such as O-U noise by the jump model (namely, ψ(t, a) and ρ(a, b)) is given, which makes it possible to apply the stochastic trajectory technique and the definition method to the above noises.

This paper deals with systems driven by correlated colored noises. The evolution equations for both the single and joint probability distribution functions are derived. It is shown that both the stationary and dynamical properties of the systems are affected by correlated colored noises. These results are obtained by means of the systematic use of the ordered cumulant-expansion technique.

A quark-quark interaction is derived from the linear expression of Lagrangian which is invariant under the SU(3)_L × SU(3)_R infinitesimal transformation, and further used to make a unified study on the N-N and Y-N scattering processes.

The Incomplete-Fusion-nagmentation Model has been used to reproduce nicely the experimental evidence of liquid-gas phase transition probed in the reaction of Au + Au at 600A MeV. The analysis of the relative yields of decay modes for the projectile remnant as a function of bound> shows clearly the competition and transformation processes of various decay modes of projectile remnant with decreasing of bound>. The agreement between theoretical and experimental results for the anaJysis of relative yield of decay modes indicates that the experimental evidence of liquid-gas phase transition is composed of the decay mode transformations.

A new set of fractional parentage coefficients is introduced to build the orthogonal basis of states with many S and D pairs in the microscopic theory of low-lying collektive motion in nuclei.