理论物理通讯

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The Spectra of Two-Electron Quantum Dot: Shifted 1/N Method

Mohammad El-Said

理论物理通讯. 1999, 31(3): 321-326.

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The spectra of two-electron quantum dot in a magnetic field of arbitrary strength is studied by using the shifted 1/N expansion method. The comparisons show that our results are in good agreement with the results of fixed-phase quantum Monte Carlo method and exact ones [Bolton, Phys. Rev. B54 (1996) 47801.

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Unified Calculations of the Energy and EPR Spectra and Their Pressure-Induced Shifts of Ruby

MA Dongping, ZHANG Hongmei, LIU Yanyun, CHEN Jurong, MA Ning

理论物理通讯. 1999, 31(3): 327-334.

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By taking into account the effect of variation in angular wavefunction, reconsidering the expressions of spin-orbit coupling parameters, diagonalizing the complete d³ energy matrix in a trigonally distorted cubic-field and using the wavefunctions from it, the unified calculations of the energy spectrum and EPR spectrum for ruby and their pressure-induced shifts have been carried out. All the calculated results are in very good agreement with a lot of experimental data. The estimation by making use of superposition model has also demonstrated the high sensitivity of trigonal-field parameters to angular variation. The distinct differences in magnitude and/or sign of pressure-induced shifts of various levels are immediately determined by their characteristic dependencies on the parameters of interactions. The pressure-induced shifts of levels and g factors have provided important criteria for the correctness of calculations and assignments of the energy spectrum and wavefunctions.

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On the Optical Conductivity of Kondo Insulators

ZHU Li, LI Zhengzhong, XIAO Mingwen

理论物理通讯. 1999, 31(3): 335-340.

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The temperature-dependent optical conductivity of a Kondo insulator for different temperatures with impurity doping on the conduction band is studied within the U = ∞ Anderson lattice model in the framework of a slave-boson mean-field theory under the coherent potential approximation. The results show that the depletion of the optical conductivity in low-frequency region decreases with increasing of the temperature, and the system exhibits a transition between a low-temperature insulating phase and a high-temperature metallic phase. With increasing of the impurity concentration, the effect of the impurity scattering could result in a nearly temperature-independent gap behavior. The numerical results on the localization of the electron and its variation with temperature are also discussed with the help of optical sum rule.

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Modulational Instability and Energy Localization in a Chain of Interacting Frenkel Excitons

XIAO Yi, HAI Wenhua

理论物理通讯. 1999, 31(3): 341-346.

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The modulational instability in one-dimensional molecule chain of interacting Frenkel excitons is investigated. The formation of localized modes via modulational instability is predicted and the previous numerical and analytical results are explained. The Peierls-Nabarro (PN) potential barrier for the localized modes is also discussed.

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Formulation of Optical Quantum Nondemolition Criteria in Linearized Systems

WANG Kaige, YANG Guojian

理论物理通讯. 1999, 31(3): 347-354.

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Abstract We apply the quantum regression theorem and the input-output relation of the single-ended cavity to the linearized systems, and formulate the optical quantum nondemolition (QND) criteria. In an application, we discuss squeezing and QND nature for a crossed Kerr dispersive model.

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Study on the Quantum FK Model

XU Aiguo, WANG Guangrui, CHEN Shigang, ZHANG Guangcai

理论物理通讯. 1999, 31(3): 355-360.

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In this paper, we present a variational method which is suitable for investigating the quantum fienkel-Kontorova model. For the cases of using the coherent state and the squeezed state as the trial wave functions of the ground states, the quantum Hamiltonians and the quantum maps are given. For the second case, we present the phase diagram and devil's stairs using the effective potential method, determine the critical points K_c for different l using Greene's criterion. The results given in the present paper are qualitatively consistent with those of the numerical experiments.^[6]

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Analytical Study of the Antiferromagnetic Heisenberg Films

LIU Shi'an CHEN Tianlun, LI Hong

理论物理通讯. 1999, 31(3): 361-366.

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With the variational cumulant expansion (VCE) method, the thermodynamic behaviors of S = 1/2 antiferromagnetic Heisenberg films in simple cubic lattices are studied analytically. From the analytic properties of the free energy, in principle we are able to calculate analytically the critical temperatures T_c(L) and the thermodynamic functions, to any order cumulant as the functions of the number of L (the hyperlayers in the hyperfilm). Explicit expressions for T_c(L) up to the fourth order are given. A comparison with the existing results for 3-dimensional system is given. The effective range of the interactiori is obtained from numerical results.

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Continuous Replica Symmetry Breaking in Critical Phenomena in Disordered Ferromagnets

WU Xintian, GONG Changde

理论物理通讯. 1999, 31(3): 367-372.

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The replica symmetry breaking (RSB) in critical phenomena in disordered ferromagnets is studied. We modified the assumption of Dotsenko et al. about the local minimum solutions of the Hamiltonian with random temperature. It is shown explicitly that the continuous RSB is generated in the renormalization group (RG). The physical regime of the coupling constants are investigated through the RG equations.

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The Fractal Characteristic of Particles in Granular Material Flows and Its Effect on Effective Thermal Conductivity

ZHANG Duanming, ZHANG Zhi, YU Boming

理论物理通讯. 1999, 31(3): 373-378.

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According to the fact that many pulverized particles possess fractal characteristic, a fractal model for studying fine particles in granular material flows is first proposed. An expression of particles' fractal distribution is derived to describe the relationship between the particle fractal dimensions and particle velocity distribution function. In accordance with this model, the theoretical particle effective thermal conductivity is derived. The analytical results show that for the small Biot-Fourier number, the effective thermal conductivity increases with the square root of the granular temperature. For very large Biot-Fourier number, the effective thermal conductivity linearly increases with the granular temperature. Numerically calculated results show that the thermal conductivity increases with the particle size fractal dimensions and decreases with the particle surface fractal dimensions.

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Quantum Invariants for Solving the Time-Dependent Schrödinger Equation in One Dimension

LI Bozang, WANG Shi'en, ZHANG Lingyun, ZHANG Xiangdong

理论物理通讯. 1999, 31(3): 379-382.

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Extending the work of Lewis and Leach on classical invariants for solving the classical equation of motion in one-dimensional system, the quantum invariants in polynomial form of momentum are obtained. The involved Hamiltonian is time-dependent and quadratic in momentum.

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The Investigation of Gauge Transformations in the SLq(2) Gauge Field and Thermodynamics Model

YAN Jun, QIU Xiaoming, TAO Biyou

理论物理通讯. 1999, 31(3): 383-390.

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Some problems about global transformations in the SLq(2) gauge field and correlative thermodynamics model have been investigated in this paper. We proved that the quantum trace of gauge potential is not gauge-invariant if we compose two GLq(2) gauge transformations. In addition, it has been discovered in SLq(2) thermodynamics model that thermodynamics average of an observable quantity does not satisfy similar gauge invariance. We also found that the thermodynamics average can be only calculated in the case of zero energy gap. This fact shows that the q-deformed energy equation in superconductivity theory is unable to derive naturally from quantum trace model.

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Quantum Phase and Phase Difference for Fermion

LIU Shengdian, ZHANG Xiong, HOU Guang, ZHANG Yongde

理论物理通讯. 1999, 31(3): 391-396.

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In this paper, from the index theorem, we present the Hermitian phase operator for fermion, give its eigenvalues and orthogonal, normalized and complete eigenstates. Furthermore, we also get the phase difference operator for two fermions and discuss its quantum properties.

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The Born-Oppenheimer Approximation to the Wave Operators

Armin Kargol

理论物理通讯. 1999, 31(3): 397-402.

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We apply the Born-Oppenheimer approximation to a scattering problem. We consider a diatomic molecule with short-range potential separating into two atoms. Using our earlier mathematicd results we construct a leading order expansion to the wave operator for this scattering channel. We comment on limitation and possible extensions of this work.

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Nonlinear Deformed Algebra Realized in a Physical System

CHEN Jingling, LU Jingfa

理论物理通讯. 1999, 31(3): 403-406.

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We show that nonlinear deformed algebra can exist in a physical system with Poschl-Teller potential. Due to this algebra, the eigenvalue problem of the system can be exactly solved by operator method. The raising and lowering operators satisfying this algebra are constructed. And the physical meaning of two deforming functions involving in this algebra is given. In addition, the SU(1,1) symmetry is exhibited in such a system by the operator method.

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Temperature-Dependent Imaginary Part of the Off-Shell Nucleon Self-Energy and the Second Order Correction of Real Part of the Nucleon Self-Energy

HAN Yinlu, SHEN Qingbiao, ZHUO Yizhong, SUN Xiuquan

理论物理通讯. 1999, 31(3): 407-414.

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The imaginary part of the off-shell nucleon self-energy at finite temperature in nuclear matter, where the polarization and correlation contributions of exchanges of the meson are taken into account, is investigated based on Walecka's meson-nucleon model and thermofield dynamics. The second order correction of temperature-dependent real part of the nucleon self-energy is calculated in terms of the dispersion relation. The Schrodinger equivalent potential of relativistic microscopic optical potential of a nucleon at finite temperature in nuclear medium is also studied.

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Microscopical Studies of the Energy Staggering in γ-Soft Nuclei

LIAO Jizhi

理论物理通讯. 1999, 31(3): 415-420.

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The energy staggering in γ-or quasi γ-band of γ-soft even-even nuclei is studied with the approximate angular moment um projection of the deformed Hartree-Fock (DHF) states. In the calculations of DHF states the modified surface &interaction matrix elements are used. It is found that in the K = 2 band produced by the angular momentum projection of DHF state the energy staggering appears only in certain conditions. Some points concerning with the angular momentum projection of K = 2 DHF states are discussed. The energy spectra of nuclei ⁷⁴Se and ⁷⁶Kr are calculated and compared with the experimental data, which show the staggering pattern of γ-soft rotor, the coincidence between them are fairly good.

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A New Expression for Nuclear Rotational Spectra

PAN Feng, LUO Yan'an, J. P. Draayer

理论物理通讯. 1999, 31(3): 421-428.

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A new formula, which is derived from a deformed rotor model for describing nuclear rotational spectra, is analyzed. The ground band of most even-even rare-earth and actinide nuclei are accurately reproduced using a damped nonlinear least-square fitting procedure for determining parameters of the theory. The results show that energy spectra obtained from a deformed rotor model are more accurate than those from a three-parameter formula based on perturbation theory.

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A Study on the Search for 1^-+ Exotic Hybrid in J/Ø Decay Process

SHEN Qixing, CHAO Mingand YU Hong

理论物理通讯. 1999, 31(3): 429-434.

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The suggestion on the search for 1^-+ exotic hybrid in a particular J/Ø decay process has been presented. We give the moment expressions for the cases of the boson resonance X with various spin-parity JXC produced in this J/Ø decay process in terms of the generalized moment analysis method. The result shows that using these moments we can identify the 1^-+ exotic hybrid produced in this kind of J/Ø decay process except for some special cases.

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Relativistic Description of Heavy Quarkonium Dissociation in Hot Matter

ZONG Hongshi, GU Jianzhong, ZHANG Xiaofei, LIU Yuxin, ZHAO Enguang

理论物理通讯. 1999, 31(3): 435-440.

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The mass spectrum and binding radii of heavy-quark bound states are analyzed in terms of the reduced Bethe-Salpeter equation. The critical values of screening masses for cc and bb bound states at finite temperature are obtained and compared with the previous results given by nonrelativistic models.

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Semiclassical Quasilinear Equation of Turbulent QGP and Non-Abelian Quasilinear Diffusion

ZHENG Xiaoping, LI Jiarong

理论物理通讯. 1999, 31(3): 441-448.

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After the concept of turbulent QGP is introduced, the quasilinear equations for turbulent QGP are given. Starting from the field equation, we still treat the collective modes as plasmons that satisfy a transport equation. Using the quasilinear equations for quarks and gluons and the transport equation for plasmons, the collisionless diffusion is discussed. We obtain the quasilinear drag coefficient and the diffusion coefficient.

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Three-Body Amplitudes of the Process a₂(1320) → π⁺π⁺π^-

ZHU Jiejie, RUAN Tunan

理论物理通讯. 1999, 31(3): 449-452.

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We analyze the decay amplitudes of the process a₂(1320) → π⁺π⁺π^- using the tensor analysis technique and show how to obtain three-body amplitudes. The derived amplitudes can describe both the resonance and the background contribution of the process.

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The Pulsational Instability of Non-Isothermal Magnetized Accretion Disk with Self-Gravity in the Transition Zone

LU Ye, YANG Lantian, YANG Pibo

理论物理通讯. 1999, 31(3): 453-458.

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By analyzing the fifth-order dispersion relation, the influence of coupled magnetic field and self-gravity on the pulsational instability of gas pressure dominated accretion disk is investigated. Our main results are that the viscous modes become more stable with the increase of self-gravity, magnetized field and viscosity, while they enhance the instabilities of acoustic modes. The effect of self-gravity to the instability is much greater than that of magnetic field in transition zone of the accretion disk. Especially, the self-gravity affects the thermal-modes and acoustic modes strongly. Finally, we discuss our results.

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Scaling Laws at the Extremal Limit of Dilaton Black Holes

CAI Ronggen, QIAO Lingzhi

理论物理通讯. 1999, 31(3): 459-464.

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The thermodynamics of an arbitrary dimensional charged dilaton black hole is investigated. We find that the extremal limit of the black hole is a critical point and the entropy of the black hole is a homogeneous function. Thus the scaling laws hold at the critical point and a phase transition is expected to appear from the extremal to nonextremal dilaton black holes. Some relevant critical exponents are given and they depend manifestly on the content of the theory.

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Quark-Quark Interaction with Confinement Terms in a QCD-Based Model Field Theory

LÜ xiaofu, LIU Yuxin, ZONG Hongshi, ZHAO Enguang

理论物理通讯. 1999, 31(3): 465-468.

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Based on the determined bilocal field in the global color symmetry model, the effective quark-quark interaction is deduced explicitly in this letter. The result shows that, except for the normal one-π and one-σ exchange terms, the confinement terms with screening factors can automatically be obtained.

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Geometry and Entropy of Two Kinds of Extreme Kerr-Newmann Black Holes

WANG Bin, SU Rukeng

理论物理通讯. 1999, 31(3): 469-472.

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Geometric and thermodynamical properties of two kinds of extreme Kerr-Newmann black holes have been investigated. We find that different values of entropy appear for these two kinds of extreme black holes and these results have close relation to their geometry.

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New Bosonic Fock Representations of Affine-Virasoro Algebras

ZHAO Jintao, LIU Xufeng

理论物理通讯. 1999, 31(3): 473-476.

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New bosonic Fock representations of the Virasoro algebra with nonzero centres are explicitly presented. Based on these, new Fock representations of affine-Virasoro algebras are constructed.

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Mapping of Householder Transformation in Euclidean Space to Rotation-Reflection Operator

FAN Hongyi, LI Liangshi

理论物理通讯. 1999, 31(3): 477-480.

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By virtue of the technique of integration within an ordered product (IWOP) of operators we maoifestly show that Householder transformation in 3-dimensional Euclidean space directly maps to the normally-ordered rotation-reflection operator. A new "dyad" form of it in three-mode Fock space is also deduced.

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1999年, 第31卷, 第3期　
刊出日期：1999-04-30

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1999年, 第31卷, 第3期 刊出日期：1999-04-30

1999年, 第31卷, 第3期　
刊出日期：1999-04-30