理论物理通讯

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Investigation on the Ground State of the Hubbard Model

Gang SU, Mo-Lin GE

理论物理通讯. 1992, 17(1): 1-6.

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The absolute ground states of the Hubbard model are explicitly presented within the framework of pseudospin when U > 2μ and U < 2μ. It is shown that the states do not possess true off-diagonal long-range order in the two cases. It is also discovered that in the ground states the U(1) phase symmetry of the Hubbard model is spontaneously broken away from the half-filling, and the total spin is zero, which is independent of the sign of U and the electron filling in the considered periodic lattice.

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Soliton Excitations in the Compressible Heisenberg Spin Chain: A General Approach

Guo-Xiang HUANG, Zhu-Pei SHI and Xian-Xi DAI, Rui-Bao TAO

理论物理通讯. 1992, 17(1): 7-20.

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A general approach is given for the nonlinear excitations in the compressible Heisenberg ferromagnetic chain in coherent-state representation. It is shown that the relative ratio of ε to δ is very important for determining the nonlinear modified terms of the equations of motion. ε = 1√S (S is the spin length) and δ = α/λ₀ (α is the lattice constant and λ₀ is the characteristic wavelength of the excitations) are two small dimensionless parameters used in the semiclassical approximation and in the long wavelength approximation, respectively. In the case of δ = O(ε), the reduced equations of motion are solved exactly and spin soliton and elastic kink solutions are obtained. The other cases of the relation between δ and ε are also discussed and the solitary wave solutions are also given. The result obtained by Ferrer, as a special case, has been included in our approach.

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The Mean First-Passage Time of the System Driven by Non-Markovian Multivalued Noises

Wen-Qing LI, Li CAO and Da-Jin WU

理论物理通讯. 1992, 17(1): 21-30.

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We generalize the method for the calculation of the mean first-passage time (MFPT) developed by Weiss et al.^[1] to the situations where the processes are driven by non-Markovian multivalued noises. For simplicity, we restrict ourselves to three cases: the noises have rectangular, long-tail and combined temporal distributions. The concrete calculations of MFPT are made with an important example and explicit analytical expressions are obtained.

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Phase Transitions of Thermal Squeezed states

Jian-Bin WU and Wen-Zhou LI, H. Umezawa

理论物理通讯. 1992, 17(1): 31-38.

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By using thermo field dynamics, we studied the phase transitions of thermal squeezed states. Two critical points are obtained in certain cases. They correspond to the transitions from thermal squeezed state to pure squeezed state and to thermal state respectively.

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Colored Noise Induced Nonequilibrium Transition in a New Chemical Oscillator

Jin-Qing FANG, J.E. Pearson

理论物理通讯. 1992, 17(1): 39-48.

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The effects of colored noise on a new chemical oscillator in CSTR are studied by computer simulation. Colored noise induced nonequilibrium transitions from one limit-cycle to two and more than two limit-cycles when the correlation time and the intensity of noise are varied. Chemical chaos is also observed.

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Soliton Chain Solutions to the Two-Dimensional Higher Order Korteweg-de Vries Equations of Sawada-Kotera Hierarchy

Ying WU and Xiao-Xue YANG

理论物理通讯. 1992, 17(1): 49-52.

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A series of two-dimensional equations with the two-dimensional Korteweg-de Vries equation being their first one are constructed as Sawada-Kotera did in one-dimensional case. Their soliton chain solutions are obtained and investigated.

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The Multi-Pole Neveu-Schwarz Algebra on Riemann Supersphere

Zhe CHANG

理论物理通讯. 1992, 17(1): 53-60.

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According to the Riemann-Roch theorem, we construct bases H_-n⁽ⁱ⁾ and N_-m^(f), for the meromorphic λ = -1 and λ = -1/2 differentials on the Riemann sphere S². The dual bases, A_-n⁽ⁱ⁾, and D_-m^(j), of these meromorphic λ differentials on C_r curves are defined. Expanding the component fields TB(z) and TF(z) of the stress-energy tensor T(z) in the superconformal field theory by the dual bases A_-n⁽ⁱ⁾, and D_-m^(j), respectively, we obtain a series of expanding coefficients. The commutation relations among these coefficients are given explicitly, which,is just the multi-pole Neveu-Schwarz algebra with central extensions on the Riemann supersphere S. Physical implics tions of the algebra are also discussed.

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QCD Interpretations of the EMC Effect

Jian-Jun YANG, Ya-Bo ZHU and Hong-Qing SHEN, Guang-Lie LI and Jian-Ping SHEN

理论物理通讯. 1992, 17(1): 61-66.

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In this paper, we give the dynamical description of the EMC effect with parton evolutionmodel (PEM), and calculate the ratios of the average nuclear structure functions of nuclei¹²c, ⁵⁶Fe, ⁶⁴Cu and ¹¹⁶Sn to the deuteron structure function by considering the shadowingeffect and Fermi motion correction with nuclear momentum conservation.

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The Soliton-Like Solutions of ø⁶ and ø⁴+ø³ Models with and Without Dissipation

Sen-Yue LOU, Guang- Jiong NI, Guo-Xiang HUANG

理论物理通讯. 1992, 17(1): 67-78.

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Besides the ø⁴ theory, the ø⁶ model and the ø⁴ + ø³ model are also useful in physics. Some specific types of solutions of them can be obtained from the solutions of ø⁴ model. The important solutions previously known are the special examples of ours. The dissipation equations of these models are also studied. The results indicate that the friction effects spread the singular solutions with velocity υ = 1 (Heaviside function) of the undamped equations such that they are nonsingular and their velocities are lower than one.

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Thermodynamic Potential of Relativistic Electron Plasma

Hong-Hua XU, Chien-Hua TSAI

理论物理通讯. 1992, 17(1): 79-88.

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Within the real time formalism of quantum field theory at finite temperatures based on the closed-time-path Green's function approach, a closed analytical expression of the thermodynamic potential of a relativistic electron plasma is derived under the random phase approximation by summing up all ring diagrams. The result is natural extension to the relativistic case sf our previous formula derived in the case of a Coulomb gas.

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Generalized Winding Number of a Dynamical System

Wei WANG, Xi-Xian YAO

理论物理通讯. 1992, 17(1): 89-92.

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The generalized winding number of the BW model system stimulated by a periodic current is studied in this letter. As long as the attractors lie on the invariant torus, the winding number diagram shows the well-known devil's staircases scenario. When the system transits to chaotic state, the winding number becomes irregular.

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The Dynamical Behaviour of the BVP Model with a Quasi-Periodic stimulation

Wei WANG, Xi-Xian YAO

理论物理通讯. 1992, 17(1): 93-96.

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The dynamical behaviour and the threshold phenomenon for the Bonhoeffer-van der Pol model of a nerve membrane stimulated by a quasi-periodic current are investigated. Our results show that there are two- and three-frequency quasi-periodic, and chaotic as well as nonchaotic (with a strange attractor) oscillations.

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The Ground State Energy of Shallow Donor Impurity Near a Crystal Surface

Zhong-Jun SHEN and Xiao-Zhong YUAN

理论物理通讯. 1992, 17(1): 97-102.

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In this letter we have studied the effect of image potential on the ground state energy of a shallow donor impurity near a sharp surface of a semi-infinite crystal. The energy expression of the system as a function of its position is calculated with the variational method. The results are discussed.

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Two-Site Effective Field Approximation for Mixed Spin Ising Model

Xiao-Ming WENG, Zhen-Ya LI

理论物理通讯. 1992, 17(1): 103-106.

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A simple and powerful method (two-site effective field approximation) for mixed spin Ising model was presented. Our result about transition temperature of mixed Ising spin system is much better than that by making use of other approximate methods.

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Exact Ground State Solution for Anyons with spin-1/2

Shun-Qing SHEN, J. CAI, Rui-Bao TAO

理论物理通讯. 1992, 17(1): 107-110.

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We solve the problem of anyons with spin-1/2 in an external field and obtain one of exact wavefunctions for its ground state, which is highly degenerated. Using Laughlin's plasma analogy, we find that there exists the algebraic off-diagonal long-range order for the ground state wavefunction in a certain external magnetic field.

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Numerical Studies on a Static Vacancy on a 2D spin-1/2 Heisenberg Antiferrornagnet Using a Projector Method

Gang SUN and Wu-Yan LAI

理论物理通讯. 1992, 17(1): 111-114.

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We study the problem of a static vacancy on a spin-1/2 Heisenberg antiferromagnetic square lattice of size 4 × 4 exactly by a projector method. We find that the nearest-neighbor spin correlations. deviate from that of the pure model at the neighborhood of the vacancy, and tend to it vibratively as the Manhattan distance from the vacancy increases.

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Irreducible Representation of Quantum SLq(3) Algebra (Ⅰ)

Zu-Rong YU

理论物理通讯. 1992, 17(1): 115-118.

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The explicit forms of the irreducible representation matricea for the quantum SLq(3) enveloping algebra are computed in analogy to the irreducible tensor technique in the classical SU(3) algebra.

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Damping of Single-Particle in Slab Model at Finite Temperature

Wei-Zhi HUANG, P.F. Bortignon, R.A. Broglia

理论物理通讯. 1992, 17(1): 119-122.

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The temperature dependence of the self-energy of a particle is studied in semi-infinite nuclear matter by making use of interactions constrained by self-consistency. Using the finite temperature Green's function Matsubara formulism, and applying the theory of slab model to the single-particle states in ²⁰⁸Pb, the calculated results show that the imaginary parts of the self-energy of a particle at Fermi energy linearly increase with the increase of temperature.

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A Comparison of Fermionic with Bosonic Form in the Anomalous Chiral Schwinger Model

Jian-Ge ZHOU and Yao-Yang LIU, Qing-Hai DAI

理论物理通讯. 1992, 17(1): 123-124.

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The two-point Green function of the scalar field is first calculated exactly by the path integral method. Unlike the fermionic form, there is no ultraviolet divergence for the scalar field Green function. The divergent structure of the fermionic form is different from that of the corresponding bosonized form.

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Effects of R□R Term in High Dimensional Inflation

Yuan-Jie LI and Zhi-Jun WANG

理论物理通讯. 1992, 17(1): 125-128.

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In this paper the R□R term is introduced to a high dimensional spacetime. We obtain various inflations at large R and □R～R^m for all anisotropic Bianchi types except IX. If the dimension of spacetime is larger than 2 but less than 6, the inflation will be inflation of power-law in flat Robertson-Walker metric.

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1992年, 第17卷, 第1期　
刊出日期：1992-01-30

模态框（Modal）标题

选择文件类型/文献管理软件名称

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1992年, 第17卷, 第1期 刊出日期：1992-01-30

1992年, 第17卷, 第1期　
刊出日期：1992-01-30