理论物理通讯

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Nonlinear Theory of Many Effective Two-Photon Correlat ed-Spontaneous-Emission Lasers

Hong-Bin HUANG

理论物理通讯. 1996, 26(2): 129-134.

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In this paper, we transform the nonlinear density matrix equation for many effective twophoton correlated-spontaneous-emission laser field obtained recently by the author to the Fokker-Planck equation, and then discuss the inffu ence of atomic coherences and the number of lower almost degenerate atomic levels on the lasing without inversion and noise reduction or phase squeezing of the field.

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The Structure of Energy Matrix and the Ground State for Two-Dimensional Hubbard Model

Ke-Cai ZENG, Zhen-Qing YANG, Fan-Mei KONG

理论物理通讯. 1996, 26(2): 135-140.

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By constructing a series of ideal matrices which possess the same properties as a real energy matrix of two-dimensional (2D) U = ∞ Hu bbard model does, the dependence of the lowest energy eigenvdue on the strudture of matrix is studied. It is found that the disorder of the distribution of a large number of off-diagonal blocks trends to even the lowest energy state and the so-called d-state. Thus degenerate ground states of various S² will be obtained in the thermodynamic limit.

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Electron Distribution and Collective Resonances in Sodium clusters

Xiao-Shuang CHEN, Ji-Jun ZHAO, Guang-Hou WANG

理论物理通讯. 1996, 26(2): 141-144.

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Electron distribution and collective resonances of sodium metallic clusters, with the inhomogeneous jellium model, are studied by means of the Thomas-Fermi statistical method with a Wood-Saxon charge distribution for positive charge background and the sum-rule formalism.The density distribution of the valence electrons has been calculated for small sodium clusters and the "redshift" effect of collective resonances is found in agreement with the experimental results. The characteristic electronic shell effects of sodium clusters are found, which cannot be obtained by using homogeneous jellium model. The collective resonances in medium sized sodium clusters are predicted and the "redshift" effect decreases as cluster size increases.

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Interface Polaron Within Parallel Electric and Magnetic Fields

Chuan-Yu CHEN, Pei-Wan JIN, Shi-Dong LIANG

理论物理通讯. 1996, 26(2): 145-152.

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A combinative method of variational wavefunction and harmonic oscillator operator algebra is used to treat the interface polaron in a semi-infinite polar crystal within parallel electric and magnetic fields perpendicular to the interface. Both the bulk longitudinal optical phonon and the interface optical phonon together with the anisotropic mass of the electron are included. The energy level correction up to the second-order perturbation, cyclotron-resonance frequency and cyclotron mass are expressed as functions of the electric and magnetic fields and a parameter characterizing the mean distance of the polaron from the interface. This theory is used to calculate numerically the single heterostructure AlAs/GaAs, when the electron is at the X high-symmetry point of the conduction band of AlAs. The results show that the magnetic field greatly enhances the polaronic correction of the electron energy levels while the electric field only increases the correction of their surface optical phonon part but obviously decreases that of their bulk optical mode part and thus the total energy correction decreases as the electric field increases. The change of red shift due to the electron-phonon interaction with electric and magnetic fields is also obf ained.

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Magnetization Curve for One-Dimensional Hubbard Model in Critical Region

Y. J. WANG, M. R. LI, C. D. GONG

理论物理通讯. 1996, 26(2): 153-158.

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A power series expression of the exact solution of the one-dimensional (1D) Hubbard model in an external magnetic field is derived to study the an tiferromagnet-ferromagnet transition in the critical region. Aside from the magnetization curve, the critical field and susceptibility are analytically evaluated, and the results of these quantities in some limiting cases are discussed.

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Soliton Lattice in Trans-Polyacetylene with Random Site-Type impurities

R. Y. JIA, L. G. YAN, G. TANG

理论物理通讯. 1996, 26(2): 159-164.

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In order to understand the effect of disorder of impurities in doped trans-polyacetylene, we investigate the electronic states of trans-PA with random site-type impurities, especially, taken into account the Coulomb interaction between impurity ions. The randomness of impurity ions can obviously affect the electronic structures of trans-PA chain for the intermediate doping regime (y ≈ 4~8%). With increasing doping level, this in turn leads to widen the soliton band and narrow the band gap. Moreover, the upper gap will appear a maximum at the critical doping level (y ≈ 6%). In addition, when the doping concentration is larger than 12%, the random distribution of impurities tends to be uniform because of being concerned with the Coulomb interaction between ions. Meanwhile, the order parameter configuration indicates that it will appear soliton lattice.

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Study of Wavefunction in the Aubry Model in l-d

Fu-Min YANG, Jin-Zuo SUN, Liang-Bin HU

理论物理通讯. 1996, 26(2): 165-173.

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Wavefunctions of the Aubry model are investigated systematically by means of the numerical method. Our results indicate that except the eigenstates located at about center of each subband, the wavefunctions of the eigenstates have fairly regular envelopes. The shape of each envelope is not relative to the length and the approximate periods of the system. In the process of transition from extended to localized states the regular shapes of the envelopes are damaged gradually and destroyed finally. This result is contrary to the conclusion given by the other authors

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The Critical Behavior of the Ising Model on Union Jack Lattice

Fu-Gao WANG, Jia-Zhen HU

理论物理通讯. 1996, 26(2): 175-180.

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In this paper, we have investigated the critical behavior of the ferromagnetic Ising model on union jack lattice. The model is equivalent to the eight-vertex model which can be solved as a free fermion model with the free fermion approximation. The critical exponents have been obtained as aα = α = 0, β = β'= 0.125, γ = γ' = 0.875 and δ = δ' = 8.

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Ising Model on Tangled Chain, Some Thermodynamic Properties

R. Mejdani

理论物理通讯. 1996, 26(2): 181-190.

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In this paper we consider an Ising model on tangled chain, where some additional bonds compared to a pure Ising chain are presented. To understand the behavior of this system and the competition between ferromagnetic bonds J along the chain and antiferromagnetic bonds J' across the chain, we have studied in detail analytically and iteratively some of the thermodynamic quantities. Particularly interesting is, in the zero-field and zero-temperature limit, the behavior of the magnetization and the susceptibility closely related to the groundstate configurations and their degeneracies. This degeneracy, presented at the condition J'≤ J between J and J', explains, also, the existence of nonzero entropy at zero temperature. This model applied as a lattice gas model defined on a tangled chain could be also useful for the experimental investigations in studying the saturation curves for the enzyme kinetics or the melting curves for DNA-denaturation.

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Numerical Evidence of Quantum Correspondence to the Classical Ergodicity

Quan-Lin JIE, Gong-Ou XU

理论物理通讯. 1996, 26(2): 191-196.

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Numerical experiment in Lipkin model shows that, in quantum system with global chaotic classical limit, the temporal mean of the expectation value of an observable is approximately equal to the average over the basic states of Hilbert space, if the wavefunction is initially either a coherent wave packet or the common eigenstates of a complete set of observables, and the observable is independent of the Hamiltonian. The mechanism is the absence of KAM barrier which prevents the spread of wavefunction. This can serve as a quantum signature of classical chaos.

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The Unitarity of the W⁽³⁾ Algebra from SU(3) Parafermion

Xiang-Mao DING, Heng FAN, Kang-Jie SHI, Pei WANG

理论物理通讯. 1996, 26(2): 197-202.

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We express the vacuum expectation value of the SU(3)k parafermion fields by that of two bosons and SU(3)_k current algebra. When k = 1,2,3, the SU(3)_k current algebra becomes an inner product of a unitary representation, and T(z), W⁽³⁾(z) are equivalent to "quasiself-adjoint" operators in this represen tation.

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Two Applications of Linear Quantum Transformation Theory in Multi-Mode Fock Space

Yong-De ZHANG, Lei MA, Xiang-Bin WANG, Jian-Wei PAN

理论物理通讯. 1996, 26(2): 203-206.

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By the aid of the linear quantum transformation (LQT), we derive all of the explicit expressions of Bogoliu bov-Valatin transformation and the rotation transformation in the case of multi-mode Fock space.

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An Explicit Moyal Product Realization of Quantum Deformation

L. N. ZHANG

理论物理通讯. 1996, 26(2): 207-212.

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The h-deformation and q-deformation were estimated completely under the concrete Moyal *-product and induced Moyal product version.

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Wu Algorithm and Eight-Vertex Solutions of Colored Yang-Baxter Equation

Xiao-Dong SUN, Shi-Kun WANG

理论物理通讯. 1996, 26(2): 213-218.

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In this note, we claim that we have obtained all nondegenerate eight-vertex-type solutions of colored Yang-Baxter equation with spectral and color parameters by several solution transformations and eight basic solutions with the help of Wu algorithm.

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The Influence of the Pion-Double-Charge-Exchange Mechanism to 0vββ Decay in 76Ge and ⁸²Se

H. F. WU

理论物理通讯. 1996, 26(2): 219-222.

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The contribution of the pion-double-chargeexchange mechanism to the 0vββ decay of ⁷⁶Ge and ⁸²Se is calculated. The lower limits of the heavy neutrino mass are obtained in different mechanisms.

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Density Isomers or Δ-Matter¹?

Guang-Jun MA0, Zhu-Xia LI, Yi-Zhong ZHUO

理论物理通讯. 1996, 26(2): 223-228.

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We demonstrate that the appearance of the density isomers depends on the meson-nucleon coupling strengths in addition to the meson-delta coupling strengths within the mean field theory. Furthermore, thein-medium NN → NΔ cross section is studied with different values of the coupling strengths for deltas. We have found that the in-medium NN → NΔ cross section substantially increases with the increasing of scalar meson-delta coupling strength even for the case when the density isomers do not appear within the mean field theory, which shows the possibility of creating Δ-matter in energetic heavy-ion collisions.

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Effects of Final-State Interactions on Inclusive Spin-Half Baryon Production from Time-Like Photon Fragmentation

Wei LU, Hai-Ming HU, Yong-Bin HE

理论物理通讯. 1996, 26(2): 229-234.

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In contrast to the hadronic tensor in the deeply inelastic scattering, we find that owing to the final-state interactions, time reversal invariance cannot make any constraint to the general expression of the photon fragmentation tensor for inclusive spin-half bafyon production. Correspondingly, there exists a novel fragmentation structure function F(z, Q²) that has no correspondence to any hadronic structure functions in the hadronic tensor of the deeply inelastic electron scattering off the spin-half baryon. Phenomenologically, F(z, Q²) determines the transverse polarization of the inclusively detected baryon in unpolarized electron-positron annihilation. In relation to the large transverse A polarization puzzle in fixed-target experiments, we suggest measuring the Λ polarization in e^- + e⁺ → Λ + X .

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Masses of Heavy Fermions and Higgs Boson in Four-Generation Fermion Condensate Scheme

Bang-Rong ZHOU

理论物理通讯. 1996, 26(2): 235-240.

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The renormalization group analyses based on low-energy effective Lagrangian indicate that a model of electroweak symmetry breaking of Nambu-Jona-Lasinio(NJL)-type by full four-generation quark-lepton condensates could accommodate itself to the topquark mass ~ 174 GeV for the acceptable momentum cutoff Λ ~ 10⁶ ~ 5 × 10³ GeV. The fourth generation of quarks will have masses in the region 228 ~ 366 GeV. The corresponding lep tons will have masses in the region 110 ~ 246 GeV and can be heavier than the top quark only if Λ ≤ 2.5 × 10⁴ GeV. The mass of the Higgs boson is predicted to be in the region 287 ~ 481 GeV which could provide an important experimental test of thf model.

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Intrinsic Loop Regularization and Gauge Invariance

Dao-Neng GAO, Mu-Lin YAN

理论物理通讯. 1996, 26(2): 241-248.

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A regularization method named the intrinsic loop regularization is proposed by WANG and GUO. Here, we apply it to the quantum electrodynamics, we find this method can remain gauge invariance very well.

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Dynamics of Two-Level Atom with Moving Mass Center Considering the Multiphoton Transitions

Xue-Xi YI

理论物理通讯. 1996, 26(2): 249-252.

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We study the effect of moving mass center on atomic dynamics for various initial conditions, and the two-level atom coupled locally in inhomogeneous cavity to a near-resonant singlemode quantized field and the atomic levels are coupled by the multiphoton transitions. Our study shows that, the Doppler effect exercised by the motion of atom can lead to the modified phenomenon of oscillation collapse and revival in the atomic population inversion at the beginning of evolution.

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A New kq Representation in Two-Mode Fock Space

Hong-Yi FAN, Yue FAN

理论物理通讯. 1996, 26(2): 253-256.

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Based on the common eigenvector of two particles' relative position and total momentumand the idea of kg representation for describing a particle in periodic lattice we construct a new representation in two-mode Fock space. Squeezing operator in this representation isstudied.

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1996年, 第26卷, 第2期　
刊出日期：1996-09-15

模态框（Modal）标题

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1996年, 第26卷, 第2期 刊出日期：1996-09-15

1996年, 第26卷, 第2期　
刊出日期：1996-09-15