理论物理通讯

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Zhi-Gang YU, Xin SUN

理论物理通讯. 1994, 21(4): 385-390.

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Using the one-band model of halogen-bridged mixed-valence transition metal complex (MX complex), within mean field theory, we have proved for fixed electron-phonon coupling, the band gap reaches the minimum at the boundary of the charge density wave state and the spin density wave state in the phase diagram. The analytic form of the ground state energy and the band gap are also obtained.

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Resonant Frequency of Impurity Polaron in a Quantum Well

BaeHua WEI, Kin-Wah YU, Shi-Wei GU

理论物理通讯. 1994, 21(4): 391-396.

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It is shown that the resonant frequency ω_c^* of a magnetopolaron bound to a Coulomb impurity in a GaAs/Ga_1-xAl_x AS quantum well is lower than that oflongitudinal optical (LO) phonons owing to the effect of the Coulomb potential. Using MacDonald method to treat the Coulomb potential we come to the conclusion that ω_c^* is really below the frequency of LO phonons but not "pinning" at a frequency near that of TO phonons.

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Exact Results for Fully Directed Flights is s-Dimensions

Guo-Ce ZHUANG, Jia-Fu WANG, Kai-Lun YAO

理论物理通讯. 1994, 21(4): 397-402.

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The critical behaviour of s-dimensional fully directed flights (FDFs) is treated by a generating function method and an exact calculation method. Our results show that the exponents v, v_|| and v_⊥ of FDFs are independent of the spatial dimensionality and the concrete form of the probability distribution of step lengths. They are in agreement with the Laplacian transformation method and the Monte Carlo simulation study for fully directed Levy flights.

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Calculation of the Binding Energy in the One-Dimensional Hubbard Model by the VMC Method

Yong-Jun LIU, Jin-Ming DONG, Chang-De GONG

理论物理通讯. 1994, 21(4): 403-408.

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Using variational Monte-Carlo method and choosing an antiferromagnetic trial wave function,we have calculated the binding energies just off half-filling in one-dimensional Hubbard chains. We found the binding for the lattice length N being less than 40 in the degenerate case, but no binding at aU in the non-degenerate case. However, with lattice length increasing gradually, difference between the two cases becomes smaller and smaller. Finally, there is no binding at all no matter whether or not the chains have a degeneracy at the Fermi level in the non-interacting (U=0) limit. It may bean in,dication of the independence of the final calculation results on the boundary conajtions for the large enough system or in thermodynamic limit.

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Acoustic Solit on in One-Dimensional Ferromagnetic Systems

Chao-Fan YU, Shu-Ren CHANG, Guo-Zhu HE

理论物理通讯. 1994, 21(4): 409-416.

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The local nonlinear excitation caused by the magnon-phonon interactions as an anisotropic source of nonlinearity is studied. The nonlinear equation for the Schrodinger probability amplitude of spin motion is given, and its soliton solutions are obtained in a weak coupling approximation. The existence conditions are discussed. It is shown that the soliton excitation energy can be less than a one-magnon state and a gap appears in the energy spectrum. The effect of the magnon-rnagnon interactions on the local acouitic soliton excitation is also discussed.

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Effects of the Bond-Bending Term and e-e Interactions on the 2D Localized Modes Around a Polaron in Trans-Polyacetylene

K. L. YAO, Z. J. LI, Z. AN, Z. L. LIU

理论物理通讯. 1994, 21(4): 417-420.

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The 2D localized modes of trans-(CH)_x around a polaron have been studied using a twodimensional extension of the SSH model that includes the bond-bending effect and the electron-electron interactions. The results show that 1) a number of additional localized modes have been found, which depend on the bond-bending term; 2) the number oflocalized modes does not change after turning on the e-e interactions, but their frequencies have been moved and the localization has been strengthened.

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An Efficient Cluster Algorithm and Its Numerical Study for the Quantum Spin systems

He-Ping YING, Da-Ren JI

理论物理通讯. 1994, 21(4): 421-428.

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Using a blockspin scheme, a cluster algorithm is developed for the numerical study of the quantum spin systems. The method is tested in detail for the ferro- and antiferromagnetic Heisenberg chains, of which our calculations show that the new algorithm can be used to simulate the induced classical spin systems efficiently by strongly reducing the slowing down effects.

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Quantum Transport Properties for Amorphous Solids with Fracton-Electron Interactions

Kai-Lun YAO, Lin YI

理论物理通讯. 1994, 21(4): 429-434.

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Based on the fracton-electron interaction, qu an t urn transport quantities are calculated by using the Hansch-Mahan quantum transport equation. Compared,with those given by the first-order and the second-order interactions of the fracton-electron, an exact conductivity expression at all temperatures for any fractal structure is'presented. In addition, the anomalous behaviour of Hall coefficient is reported.

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?(x) Matrices via New Yang-Baxterization

You-Quan LI, Jun ZHANG

理论物理通讯. 1994, 21(4): 435-440.

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Several new ?(x) matrices as solutions of Yank-Baxter equations are found via a developed trigonometric Yang-Baxterization for three eigenvalues. The consistency conditions of the new trigonometric Yang-Baxterization are obtained explicitly.

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U(1/1)_q q-Coherent States and Path Integrals for the q-Deformed Jaynes-Cummings Model

Le-Man KUANG, Fa-Bo WANG, Gaq-Jian ZENG

理论物理通讯. 1994, 21(4): 441-446.

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The q-coherent states for the quantum superalgebra U(1/1)_q, are introduced. Path integrals in the q-coherent state representations of the U(1/1)_q, are constructed and applied to the q-deformed Jaynes-Cummings model whose dynamical superalgebra is the quantum superalgebra U(1/1)_q.

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The Two-Nucleon Mechanism for the Neutrinoless Double Beta Decay and the BCS Nuclear Wave Function

Zhong-Jin LIN, You-Ping GAN, De-Ji FU, Hui-Fang WU, Chong-En WU

理论物理通讯. 1994, 21(4): 447-454.

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A method of using the Bardeen-Cooper-Schrieffer (BCS) nuclear wave function to treat the two-nucleon mechanism for neutiinoless double beta decay process 0⁺ → 0⁺ is proposed.The neutrinoless decay mode and the neutrinoless decay accompanied by a Majoron emission mode of ⁸²Se are studikd. Our cdculated results show that to reproduce the experimental value of γ^(ov) > 1.8 × 10²² yr for neutrinoless double beta decai of ⁸²Se the Majorana neutrino mass m_v < 6.2 eV and the mixing parameter of right-handed current η < 7.0 × 10^-6 In the emission with a Majoron mode the effective Majoron coupling to neutrino is deduced from the experimental value of γ^(ov,H) > 4.4 × 10²⁰ yr for ⁸²Se with the result H0> < 6.2 × 10^-4.

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Test on Application Range of QCD Sum Rules from Baryon Spectroscopy

Peng-Nian SHEN, Yu-Bing DONG, Xin-Heng GUO, Xue-Qian LI

理论物理通讯. 1994, 21(4): 455-464.

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By considering the nonperturbative QCD effect via quark and gluon condensates, the confinement terms in effective q-q potential can automatically be given. A potential in the form of (-2α,/3r) + Σ_n^∞ a_2n+1r²ⁿ⁺¹ + (Yukawa-type terms) where positive and negative signs appear alternatively in a_2n+1's is proposed. To testify the validity range of QCD sum rules, the experimental baryon spectrum is fitted and the values of azn+l's as well as their signs are obtained. It is found that in the baryon spectrum calculation, the terms of r³ snd r⁵ are important and higher terms beyond r⁵ can be neglected. Comparing these values with the result calculated from QCD sum rules, some agreements and disagreements are found.

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The Effective Mass of Nucleon in Asymmetric Nuclear Matter

Jian-Min YANG, Shou-Yong PEI, Shang-Hui GAO

理论物理通讯. 1994, 21(4): 465-470.

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The effective mass of nucleon in asymmetric nuclear matter is studied by the RHF approach.It is found that there exist critical densities ρ_c(δ). When ρ > ρ_c a phase transition from Fermi sphere to Fermi shell.pattern for ground state will occur.

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Z-Algebra Construction of W-Algebra in the Parafermion Model

Pei WANG, Chang-Yu ZHU

理论物理通讯. 1994, 21(4): 471-478.

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We propose a new construction — the Z-algebra construction for the W-algebra which includes the Virasoro algebra as a special case. The Z-algebra associated with the general affine Lie algebra is given. And we suggest a calculating program to make the derivation of the Z-algebra become possible. Using this technique we have derived the Virasoro algebra in general G_k parafermion case and the W-algebra in SU(2)_k parafermion case.

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SUSY Virtual Effects on the Production of tq at LEPPI

Yan-Sheng WEI, Chong-Sheng LI, Chao-Hsi CHANG, Jin-Min YANG

理论物理通讯. 1994, 21(4): 479-486.

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Virtual effects of supersymmetry on the-flavor changing process at LEPII are calculated in the minimal supersymmetric standard model (MSSM). We analyze the cross section of e⁺e^- → γ, Z⁰ → tq, and find that even for the most distinguishable mode e⁺e^- → γ, Z⁰ → tc, the effect is small compared with the SM expectation.

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Regular and Chaotic Spatiotemporal Patterns in a Model of Slime Mold Aggregation

Zu-Kang FENG, Jing-Hua XU, Da-Fu DING

理论物理通讯. 1994, 21(4): 487-494.

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In this paper we proposed a spatial modulated two-variable Martiel-Goldbeter model to describe the complex spatiotemporal disorder dynamical behavior during development of Dictyostelium discoideum strain FR17. As the nonlinear modulated parameter A and diffusion coefficient E varied, the system shows: 1) multiperiodic phase, 2) co-existence phase of chaotic and multi-periodic state, 3) spatiotemporal chaotic phase, 4) co-existence phase of chaotic, multi-periodic and steady state, and 5) co-existence phase of chaotic and steady state. These phases can be described by spatiotemporal power spectra, pattern distribution function and Lyapunov spectra. We believed that the complex spatiotemporal disorder dynamical behavior during development of Dictyosteliurn discoideum strain FR17 is a spatiotemporal chaotic state.

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The Effect of Noise on Pattern Dynamics During Dictyostelium Discoideum Aggregation

Zu-Kang FENG, Jing-Hua XU, Da-Fu DING

理论物理通讯. 1994, 21(4): 495-498.

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In this paper, we studied the effect of noise on pattern dynamics of the spatial modulated two-variable diffusion-reaction model. We found that the dynamical behavior becomes more complex when noise is added. The interaction between dynamic and stochastic force gives rise to the following features: 1) In spatio temporal chaotic phase, the oscillation death emerges in some spatial sites when the noise level exceeds a critical value. We call it noise-induced oscillation death. 2) In co-existence phase of chaotic and steady state, noise brings about oscillation behavior in the domain of oscillation death when its level exceeds a critical value.We call it noise-induced re-excitation of oscillation. 3) There exist alternating periodicchaotic states versus the noise level in some spatial sites. 4) There exist superstable domains.In these domains the qualitative features do not change as the noise level increases.

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The Effect of Symmetrical Energy and Shell Correction on the Cluster Formation in QMD

Jun-Qing LI, Jian-Ye LIU, En-Guang ZHAO, Quan-Ling ZHU

理论物理通讯. 1994, 21(4): 499-504.

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Based on the QMD model, in addition to the Skyrrne-type, Yukawa and Coulomb interactions,a cluster's N, Z dependent macroscopic potential, which consists of the symmetrical energy of liquid drop model and shell, pairing correction energies, has been taken into account.It improved the structure of the clusters formed in heavy ion reactions at intermediate energy.

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Lorentz Invariant Generalization of the Linear Self-Dual Constrained Theory

Yan-Gang MIA0, Yao-Yang LIU

理论物理通讯. 1994, 21(4): 505-508.

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We propose a manifestly Lorentz invariant action with a modified linear self-dual constraint, which contains a self-dual field or a free scalar field theory according to the parameter α introduced. We obtain the Floreanini-Jackiw's formulation for any values of α by imposing the linear self-dual constraint in phase space.

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A Possible Generalization of the Bargmann Space

Hong-Yi FAN

理论物理通讯. 1994, 21(4): 509-512.

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By virtue of the technique ofintegration within an ordered product of operators we show that the ordinary Bargmann space basis function zⁿ/√n! can be extended to two-variable Hermi te polynomials, the latter can span a generalized Bargmann space. The corresponding twomode Hermite polynomial states are thus introduced and their properties are investigated.

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1994年, 第21卷, 第4期　
刊出日期：1994-06-15

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1994年, 第21卷, 第4期 刊出日期：1994-06-15

1994年, 第21卷, 第4期　
刊出日期：1994-06-15