1993年, 第19卷, 第4期　
刊出日期：1993-06-15

  

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  Effects of Dipole Interaction on Emission Spectra of Atoms in Two-Photon Processes

  Zhen-Fei LUO, Zhi-Zhan XU, Lei XU

  理论物理通讯. 1993, 19(4): 385-390.

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  We study the interaction of a pair of coupling two-level atoms with a single mode of the radiation field in an ideal cavity via two-photon resonant transition and/or degenerate Ramancoupled processes.In particular, we consider the emission spectra for both two-photon processes. The effects of atomic coupling are analyzed and the properties of emission spectra for large photon number of the cavity-mode are discussed.
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  Aharonov-Anandan Phase and Superadiabatic Approximaton

  Jing-Bo XU, Dong-Hui XU, Xiao-Chun GAO

  理论物理通讯. 1993, 19(4): 391-394.

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  In this paper, the exact evolving state for a two-level quantum system is found by making use of the Lewis-Riesenfeld invariant theory. In principle, the correction to an arbitrary order in the adiabatic approximation parameter c can be obtained from this exact evolving state. To the n-th order in ∈, it is shown that the exact evolving state reduces to the superadiabatic basis introduced by Berry recently. The Aharonov-Anandan phase and its adiabatic limit (Berry phase for the system) are also calculated. e for the system) are also calculated.
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  The Finite Temperature s-Wave Superconductivity in the Two-Component Anyon Gas

  Jian ZIIOU, S. G. CHEN

  理论物理通讯. 1993, 19(4): 395-402.

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  onent anyon gas, and show that in the content of the BCS theory the long range gauge force can not be renormalized at the finite temperature T # 0, and this singularity is inherent and can not be overcome by adding other interactions of any form. We attribute this to the fake vortex excitations, and show that an elementary excitation over the supercondu&ive s-wave ground state in the two-component anyon gas is always in company with the excitation of a fake vortex. The finite temperature superconductivity in the two-component anyon gas is similar with the two-dimensional superfluid. There are two KT phase transitions.ponent anyon gas is similar with the two-dimensional superfluid. There are two KT phase transitions.
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  A Non-Equilibrium Approach to Coupled-Mode-Induced Hot-Electron Energy Loss Rate

  M. W. WU, X. L. LEI

  理论物理通讯. 1993, 19(4): 403-408.

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  Hot-electron energy loss to the lattice through electron-phonon interactions is studied using Keldysh closed-time-path Green's functions. To the lowest order in electron-phonon coupling, Kogan's formula for the energy-loss rate is obtained. When higher order interactions are included, however, we find that the coupled-mode contribution is exactly zero.
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  Energy Minigaps in the Quantum Wires with Lateral Surface Structures

  Zhen-Yan DENG, Hong SUN, Shi-Wei GU

  理论物理通讯. 1993, 19(4): 409-414.

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  Energy minigaps caused by lateral surface structures in quasi-one-dimensional GaAs/AlAs quantum wires are calculated with the variational and degenerate-pert urbational approaches. By a coordinate transformation, the structured interfaces of wires are transformed into planar ones so that the boundary conditions of the electronic wave functions can be satisfied exactly on the interfaces. The dependence of energy minigaps on lateral surface structures are discussed.
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  A Possible Pairing Mechanism in Two-Band Hubbard Model

  Mei-Rong LI, Dong-Ning SHENG, Chang-De GONG, Arno Holz

  理论物理通讯. 1993, 19(4): 415-420.

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  A theoretical scheme for describing the quasiparticle-pair superconductivity in doped CuO₂ system is suggested based on the model put forward by Emery and Reiter. The doped O holes and associated two neighboring Cu-spins form spin-1/2 quasiparticles. Through the magnetic interaction with the spin background, the quasiparticles interact with each other and lead to pair condensation which is responsible for the superconductivity.
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  Strong-Coupling System of the Electron-Ripplon on Liquid-Helium Film

  Pei-Wan JIN, Chuan-Yu CHEN2

  理论物理通讯. 1993, 19(4): 421-426.

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  The Landau-Pekar variational theory for investigating the strong-coupling system of electronphonon in crystals is employed to study the system of an electron strongly coupled to ripplons on the outer surface of the liquid-helium film. Analytical expressions of the ground state energy, the effective mass, the average number of virtual ripplons around the electron and the spatial extension of the electron are obtained. A dimensionless quantity of effective mass ratio has been introduced and compared with the model mass and the Feynman mass which exist in the literature.
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  Extension Theory for Magnon of a Ferromagnetic Superlattice

  Song PAN, Yi-Fang ZHOU, Tsung-Han LIN

  理论物理通讯. 1993, 19(4): 427-436.

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  We prove that the extension theory for lattice Green's functions can be used to study Heisenberg ferromagnetic systems. As an example, the magnon spectrum of a ferromagnetic superlat tice is calculated by the extension theory for lattice Green's functions cooperated with the transfer matrix technique. The spectrum of magnetic excitation near the surface of a ferromagnetic superlattice is also presented.
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  Non-Perturbative Energy Density Green Function in Ising Field Theory for Tc¹

  Hong-Kang ZHAO, Mu-Lin YAN

  理论物理通讯. 1993, 19(4): 437-446.

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  The leading behavior of the energy density Green function in king quantum field theory is investigated. By using the scaling theory and cluster expansion, we obtain the function of Ising field model in the presence of an external magnetic field as T→Tc- from Bariev's correlation function.
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  Coherent State Representations of Lie Superalgebra SU(2/1)

  Le-Man KUANG, Gao-Jian ZENG

  理论物理通讯. 1993, 19(4): 447-456.

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  We present a kind of new coherent states associated with the Lie superalgebra SU(2/1), and discuss their properties in detail. We also evaluate the matrix elements of the SU(2/1) generators in the coherent state representations and obtain differential realizations of the SU(2/1) algebra in the coherent state space. The differential realizations may be useful for the study of the quasi-exactly solvable problems in the quantum mechanics.
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  A System of Linear Algebraic Equations for Giving Dark Multi-Soliton Solutions of the mKdV Equation

  Nian-Ning HUANG, Zhong-Zhu LIU

  理论物理通讯. 1993, 19(4): 457-462.

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  A system of linear algebraic equations for giving dark multi-soliton solutions of the mKdV equation is formulated based upon the method of Darboux transformation. The dark 1- and 2-soliton sol u tions are given explicitly.
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  On the Summation over Lattice

  Bo NING, Xiao-Wei LIU, Zhi-Bing LI

  理论物理通讯. 1993, 19(4): 463-466.

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  In this paper, we develop an algebraic approach of evaluating summations over lattice. It would benefit us to get a series of new expressions of summation over lattice without any graphic tricks.
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  Symmetries of Fractional Parentage Coefficients with Isospin

  Hong-Zhou SUN, Qi-Zhi HAN, Jia-Jun WANG

  理论物理通讯. 1993, 19(4): 467-474.

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  A system of identical fermions with single angular momentum j and isospin 1/2 is under consideration. The classification of its wave functions, the factorization and the symmetry of fractional parentage coefficients are discussed by using the generalized Wigner-Eckart theorem of semisimple compact Lie groups.
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  Observation of CP Non-Invariance in ∑⁺→Pγ

  Xue-Qian LI, Yuan-Shan LI, Jia-Quan ZHANG, Pei-Ying ZHAO, Qiang ZHAO

  理论物理通讯. 1993, 19(4): 475-488.

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  We study the CP non-invariance in the Δs = 1 weak radiative decay ∑⁺→Pγ based on a few widely-discussed models. In the work, we study the isospin zero channel of the photon where unlike for ∑→Pπ, the CP non-invariance in ∑→Pγ is caused by the interference of the strong interaction to the weak-electromagnetic process through loops. We obtain a CP factor R = (α-α)/(α-α) of an order~10^-5 to 10^-4 which may be observed in the future.
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  Topological Conformal Field Theories from the Noncompact Coset Models

  Y. X. CHEN, H. B. GAO

  理论物理通讯. 1993, 19(4): 489-494.

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  It is shown in this letter that in the bosonic coset models G_kl×G_k2/G_kl+_k2 associated with noncompact Kac-Moody algebra there exist two kinds of topological points, _k2=0 and _kl+_k2-2g = 0. At these points, the coset models may be interpreted as twisted versions of noncompact counterparts of the Kazama-Suzuki models.
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  Two-Parameter Deformations of SU(2) and SU (1,l) Algebras

  Si-Cong JING, Frank Cuypers

  理论物理通讯. 1993, 19(4): 495-500.

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  The algebras SU(2) and SU(1,1) are promoted to two-parameter quantum universal enveloping algebras (QUEA) by a doubleparameter deformation in this paper. The discrete unitary irreducible representations and their deformed coherent states are studied. The deformed generators are given by a Jordan-Schwinger realization and a Bargmann-Fock representation. It is also interesting that the two-parameter deformed coherent states are found to relate to the oneparameter deformed ones by a simple scaling transformation and this can be used to derive the completeness relation of the former.
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  New Renormalized Multiple-Exchange-Mediated Interaction and Superconductivity

  Fu-Sui LIU

  理论物理通讯. 1993, 19(4): 501-504.

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  A new renormalized form of the multiple-exchange-mediated interaction (MEMI) and the twin-gap solution are given. A numerical example is also given.
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  The q-Analogous Vertex Operator and Quantum Affine Algebras

  Jun YAN, Shi-Ke HU

  理论物理通讯. 1993, 19(4): 505-508.

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  The extended quantum affine algebras of q-analogous vertex operator have been constructed in this Jet ter, and the similar algebra structure of q-analogous fermionic vertex operator is also analysed.
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  Generalization of Susskind-Glogower Phase Operators and Inverse Field Operators to q-Deformed Case

  Hong-Yi FAN

  理论物理通讯. 1993, 19(4): 509-512.

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  We analyze some properties of Susskind-Glogower (SG) phase operators exp(iΦ) and exp(-iΦ) by making use of inverse field operators. The generalization of the analysis to q-deformed case is given.