2013年, 第59卷, 第03期　
刊出日期：2013-03-15

  

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  Lie Symmetries of Ishimori Equation

  宋旭霞

  理论物理通讯. 2013, 59(03): 253-256.

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  The Ishimori equation is one of the most important (2+1)-dimensional integrable models, which is an integrable generalization of (1+1)-dimensional classical continuous Heisenberg ferromagnetic spin equations. Based on importance of Lie symmetries in analysis of differential equations, in this paper, we derive Lie symmetries for the Ishimori equation by Hirota's direct method.
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  An Improved Fitness Evaluation Mechanism with Memory in Spatial Prisoner's Dilemma Game on Regular Lattices

  王娟, 刘丽娜, 董恩增, 王莉

  理论物理通讯. 2013, 59(03): 257-262.

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  To deeply understand the emergence of cooperation in natural, social and economical systems, we present an improved fitness evaluation mechanism with memory in spatial prisoner's dilemma game on regular lattices. In our model, the individual fitness is not only determined by the payoff in the current game round, but also by the payoffs in previous round bins. A tunable parameter, termed as the memory strength (μ), which lies between 0 and 1, is introduced into the model to regulate the ratio of payoffs of current and previous game rounds in the individual fitness calculation. When μ=0, our model is reduced to the standard prisoner's dilemma game; while μ=1 represents the case in which the payoff is totally determined by the initial strategies and thus it is far from the realistic ones. Extensive numerical simulations indicate that the memory effect can substantially promote the evolution of cooperation. For μ<1, the stronger the memory effect, the higher the cooperation level, but μ=1 leads to a pathological state of cooperation, but can partially enhance the cooperation in the very large temptation parameter. The current results are of great significance for us to account for the role of memory effect during the evolution of cooperation among selfish players.
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  New Similarity Reduction Solutions for the (2+1)-Dimensional Nizhnik-Novikov-Veselov Equation

  智红燕

  理论物理通讯. 2013, 59(03): 263-267.

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  In this paper, some new formal similarity reduction solutions for the (2+1)-dimensional Nizhnik-Novikov-Veselov equation are derived. Firstly, we derive the similarity reduction of the NNV equation with the optimal system of the admitted one-dimensional subalgebras. Secondly, by analyzing the reduced equation, three types of similarity solutions are derived, such as multi-soliton like solutions, variable separations solutions, and KdV type solutions.
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  Solution of Dirac Equation with Generalized Hylleraas Potential

  Akpan N. Ikot

  理论物理通讯. 2013, 59(03): 268-272.

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  We employ the parametric generalization of the Nikiforov-Uvarov method to solve the Alhaidari formalism of the Dirac equation with a generalized Hylleraas potential of the form V(r)=V₀(a+exp(λr))/(b+exp(λr))+V₁(d+exp(λr))/(b+exp(λr)). We obtain the bound state energy eigenvalue and the corresponding eigenfunction expressed in terms of the Jacobi polynomials. By choosing appropriate parameter in the potential model, the generalized Hylleraas potential reduces to the well known potentials as special cases.
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  Analytical Solutions for the Two-Dimensional Gross-Pitaevskii Equation with a Harmonic Trap

  石玉仁, 王雪玲, 王光辉, 刘丛波, 杨红娟

  理论物理通讯. 2013, 59(03): 273-278.

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  Both the homotopy analysis method and Galerkin spectral method are applied to find the analytical solutions of the two-dimensional and time-independent Gross-Pitaevskii equation, a nonlinear Schrödinger equation used in describing the system of Bose-Einstein condensates trapped in a harmonic potential. The approximate analytical solutions are obtained successfully. Comparisons between the analytical solutions and the numerical solutions have been made. The results indicate that they are agreement very well with each other when the atomic interaction is not too strong.
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  Entanglement Teleportation via a Two-Qubit System with Anisotropic Couplings under a Different Nonuniform Magnetic Field

  秦猛

  理论物理通讯. 2013, 59(03): 279-284.

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  We examine entanglement teleportation, characterized by average fidelity, of two-qubit XYZ spin chain under different nonuniform magnetic field. The entanglement teleportation and the fidelity of entanglement teleportation are investigated separately. We show explicitly that the fidelity of entanglement teleportation can be enhanced by changing the direction of the magnetic field. This means that we can always get optimal fidelity by choosing the directions of magnetic field in the process of quantum teleportation. Moreover, the results show that in some cases the ferromagnetic chain also is a qualified candidate in the process of teleportation protocol.
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  Remark on the One-Way Quantum Deficit for General Two-Qubit States

  邵连合, 席政军, 李永明

  理论物理通讯. 2013, 59(03): 285-289.

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  We reinvestigate the one-way quantum deficit, which is a measure of quantum correlation emerging from a thermodynamical approach. We give a tight upper bound of the one-way quantum deficit for general mixed states, and give a sufficient condition for this bound. Finally, we discuss a universal way to evaluate the one-way quantum deficit for general two-qubit states.
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  Exact Solutions of the Two-Dimensional Cubic-Quintic Nonlinear Schrödinger Equation with Spatially Modulated Nonlinearities

  宋祥, 李画眉

  理论物理通讯. 2013, 59(03): 290-294.

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  Applying the similarity transformation, we construct the exact vortex solutions for topological charge S≥1 and the approximate fundamental soliton solutions for S=0 of the two-dimensional cubic-quintic nonlinear Schrödinger equation with spatially modulated nonlinearities and harmonic potential. The linear stability analysis and numerical simulation are used to exam the stability of these solutions. In different profiles of cubic-quintic nonlinearities, some stable solutions for S≥0 and the lowest radial quantum number n=1 are found. However, the solutions for n≥2 are all unstable.
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  Excitation Spectrum and Momentum Distribution of Bose-Hubbard Model with On-site Two- and Three-Body Interaction

  黄备兵, 完绍龙

  理论物理通讯. 2013, 59(03): 295-301.

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  An effective action for Bose-Hubbard model with two- and three-body on-site interaction in a square optical lattice is derived in the frame of a strong-coupling approach developed by Sengupta and Dupuis. From this effective action, superfluid-Mott insulator (MI) phase transition, excitation spectrum and momentum distribution for two phases are calculated by taking into account Gaussian fluctuation about the saddle-point approximation. In addition the effects of three-body interaction are also discussed.
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  Nonlinear Dynamics of Permanent-magnet Synchronous Motor with v/f Control

  韦笃取, 张波, 罗晓曙, 丘东元

  理论物理通讯. 2013, 59(03): 302-306.

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  The nonlinear dynamics of permanent-magnet synchronous motor (PMSM) with v/f control signals is investigated intensively. First, the equilibria and steady-state characteristics of the system are formulated by analytical analysis. Then, some of its basic dynamical properties, such as characteristic eigenvalues, Lyapunov exponents and phase trajectories are studied by varying the values of system parameters. It is found that when the values of the system parameters are smaller, the PMSM operates in stable domains, no matter what the values of control gains are. With the values of parameters increasing, the unstability appears and PMSM falls into chaotic operation. Furthermore, the complex dynamic behaviors are verified by means of simulation.
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  Explicit Solutions and Bifurcations for a Class of Generalized Boussinesq Wave Equation

  马志民, 孙峪怀, 刘福生

  理论物理通讯. 2013, 59(03): 307-310.

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  In this paper, the generalized Boussinesq wave equation u_tt-u_xx+a(u^m)_xx+bu_xxxx=0 is investigated by using the bifurcation theory and the method of phase portraits analysis. Under the different parameter conditions, the exact explicit parametric representations for solitary wave solutions and periodic wave solutions are obtained.
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  Nonautonomous Dark Solitons and Rogue Waves in a Graded-Index Grating Waveguide

  刘冲, 杨战营, 杨文力, 岳瑞宏

  理论物理通讯. 2013, 59(03): 311-318.

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  We analytically present a family of nonautonomous dark solitons and rogue waves in a planar graded-index grating waveguide with an additional long-period grating. The dark solitons whose dynamics described by the explicit expressions such as the valley, background and wave central position are investigated. We find that dark soliton's depth and the long-period grating have effects on soliton's wave central position; the gain or loss term affects directly both the background and valley of the soliton. For rogue waves, it is reported that one can modulate the distribution of the light intensity by adjusting the parameters of the long-period grating. Additionally, more rogue waves with different evolution behaviors in this special waveguide are demonstrated clearly.
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  Cosmology in Massive Gravity

  龚云贵

  理论物理通讯. 2013, 59(03): 319-323.

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  We argue that more cosmological solutions in massive gravity can be obtained if the metric tensor and the tensor Σ_μν defined by Stückelberg fields take the homogeneous and isotropic form. The standard cosmology with matter and radiation dominations in the past can be recovered and ΛCDM model is easily obtained. The dynamical evolution of the universe is modified at very early times.
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  Optimization of Neutrino Oscillation Parameters Using Differential Evolution

  Ghulam Mustafa, Faisal Akram, Bilal Masud

  理论物理通讯. 2013, 59(03): 324-330.

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  We show how the traditional grid based method for finding neutrino oscillation parameters Δm² and tan² θ can be combined with an optimization technique, Differential Evolution (DE), to get a significant decrease in computer processing time required to obtain minimal chi-square (χ²) in four different regions of the parameter space. We demonstrate efficiency for the two-neutrinos case. For this, the χ² function for neutrino oscillations is evaluated for grids with different density of points in standard allowed regions of the parameter space of Δm² and tan² θ using experimental and theoretical total event rates of chlorine (Homestake), Gallex+GNO, SAGE, Superkamiokande, and SNO detectors. We find that using DE in combination with the grid based method with small density of points can produce the results comparable with the one obtained using high density grid, in much lesser computation time.
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  Electron-Positron Pair Production in a Strong Laser Field Enhanced by an Assisted High Frequency Weak Field

  Abdukerim Nuriman, 谢柏松, 李子良, Dulat Sayipjamal

  理论物理通讯. 2013, 59(03): 331-334.

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  Electron-positron pair production in a strong laser field enhanced by an assisted high frequency weak field is investigated by solving the quantum Vlasov equation. The average and residual pair number densities are obtained for sinusoid electric field and it is found that the high frequency assisted weak field will enhance pair production significantly. There exists an optimal frequency of assisted field that makes the pair production number density get a maximum one, which is a few orders of higher than that without assisted field. We also discuss the other possible assisted fields.
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  Symmetry Analysis and Conservation Laws for the Hunter-Saxton Equation

  Mehdi Nadjafikhah, Fatemeh Ahangari

  理论物理通讯. 2013, 59(03): 335-348.

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  In this paper, the problem of determining the most general Lie point symmetries group and conservation laws of a well known nonlinear hyperbolic PDE in mathematical physics called the Hunter-Saxton equation (HSE) is analyzed. By applying the basic Lie symmetry method for the HSE, the classical Lie point symmetry operators are obtained. Also, the algebraic structure of the Lie algebra of symmetries is discussed and an optimal system of one-dimensional subalgebras of the HSE symmetry algebra which creates the preliminary classification of group invariant solutions is constructed. Particularly, the Lie invariants as well as similarity reduced equations corresponding to infinitesimal symmetries are obtained. Mainly, the conservation laws of the HSE are computed via three different methods including Boyer's generalization of Noether's theorem, first homotopy method and second homotopy method.
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  Cold Nuclear Matter Effects on Isolated Prompt Photon and Isolated Prompt Photon+Jet Productions in Relativistic Heavy-Ion Collisions

  代巍, 陈时勇, 张本威, 王思科

  理论物理通讯. 2013, 59(03): 349-355.

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  We investigate the cold nuclear matter (CNM) effects on isolated prompt photon and isolated prompt photon associated jet productions in nuclear collisions at the NLO accuracy by using the EPS09 NLO nuclear parton distribution functions and their error sets. Nuclear modification factors of isolated prompt photon and isolated prompt photon+jet productions due to CNM effects in p+A and A+A reactions at the RHIC and the LHC are provided with varying rapidity and transverse momentum of the final state photon. It is shown that the CNM effects on isolated prompt photon and photon+jet are modest, which give a small enhancement at low p_T region and a more obvious suppression at large p_T at central rapidity. At forward rapidity a pronounced suppression of γ as well as γ+jet is always observed.
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  The Effects of Spherical Surface and Laser Polarization on the Photodetachment Cross Section of H^-

  Muhammad Haneef, Suneela Arif, Jehan Akbar, Nasrullah Shah, Muhammad Zahir, Aneela Shamim, Hameed Ullah

  理论物理通讯. 2013, 59(03): 356-360.

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  We report the combined effects of laser polarization and curvature of the spherical surface on the detached electron spectra from H^-. The Theoretical imaging method is used as a tool of investigation. The photodetachment cross sections for various polarization angles, radii of curvatures and inter ion surface distances are displayed. The analysis of the spectra reveals that the laser polarization angle θ_L, curvature of the surface r_c and inter ion surface distance d strongly affect oscillations in the spectra. Therefore, a fine control on the laser polarization and that of curvature in the surface can be used to control oscillations in the photodetachment of negative ions.
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  Computer Simulation Study of Thermal Conduction in 1D Chains of Anharmonic Oscillators

  Tejal N. Shah, P. N. Gajjar

  理论物理通讯. 2013, 59(03): 361-364.

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  In this work thermal conduction in one-dimensional (1D) chains of anharmonic oscillators are studied using computer simulation. The temperature profile, heat flux and thermal conductivity are investigated for chain length N=100, 200, 400, 800 and 1600. In the computer simulation anharmonicity is introduced due to Fermi-Pasta-Ulam-β (FPU-β) model. For substrate interaction, an onsite potential due to Frenkel-Kontorova (FK) model has been used. Numerical simulations demonstrate that temperature gradient scales behave as N^-1 linearly with the relation J=0.1765/N. For the thermal conductivity K, KN to N obey the linear relation of the type KN=0.8805N. It is shown that thermal transport is dependent on phonon-phonon interaction as well as phonon-lattice interaction. The thermal conductivity increases linearly with increase inanharmonicity and predicts relation κ=0.133+0.804β. It is also concluded that for higher value of the strength of the onsite potential system tends to a thermal insulator.
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  Efficient Excitation of a Symmetric Collective Atomic State with a Single-Photon Through Dipole Blockade

  洪方昱, 熊诗杰, 傅景礼, 朱志艳

  理论物理通讯. 2013, 59(03): 365-369.

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  In the famous quantum communication scheme developed by Duan et al. [L.M. Duan, M.D. Lukin, J.I. Cirac, and P. Zoller, Nature (London) 414 (2001) 413], the probability of successful generating a symmetric collective atomic state with a single-photon emitted have to be far smaller than 1 to obtain an acceptable entangled state. Based on strong dipole-dipole interaction between two Rydberg atoms, two simultaneous excitations in an atomic ensemble are greatly suppressed, which makes it possible to excite a mesoscopic cold atomic ensemble into a near-ideal singly-excited symmetric collective state accompanied by a signal-photon with near unity success probability.
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  Lattice Boltzmann Simulation for Complex Flow in a Solar Wall

  陈柔, 郑友取, 俞慧丹, 许友生

  理论物理通讯. 2013, 59(03): 370-374.

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  In this letter, we present a lattice Boltzmann simulation for complex flow in a solar wall system which includes porous media flow and heat transfer, specifically for solar energy utilization through an unglazed transpired solar air collector (UTC). Besides the lattice Boltzmann equation (LBE) for time evolution of particle distribution function for fluid field, we introduce an analogy, LBE for time evolution of distribution function for temperature. Both temperature fields of fluid (air) and solid (porous media) are modeled. We study the effects of fan velocity, solar radiation intensity, porosity, etc. on the thermal performance of the UTC. In general, our simulation results are in good agreement with what in literature. With the current system setting, both fan velocity and solar radiation intensity have significant effect on the thermal performance of the UTC. However, it is shown that the porosity has negligible effect on the heat collector indicating the current system setting might not be realistic. Further examinations of thermal performance in different UTC systems are ongoing. The results are expected to present in near future.
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  RCD Large Aspect-Ratio Tokamak Equilibrium with Magnetic Islands: a Perturbed Approach

  F. L. Braga

  理论物理通讯. 2013, 59(03): 375-378.

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  Solutions of Grad-Shafranov (GS) equation with Reversed Current Density (RCD) profiles present magnetic islands when the magnetic flux is explicitly dependent on the poloidal angle. In this work it is shown that a typical cylindrical (large aspect-ratio) RCD equilibrium configuration perturbed by the magnetic field of a circular loop (simulating a divertor) is capable of generate magnetic islands, due to the poloidal symmetry break of the GS equilibrium solution.
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  Effect of Aspiration and Mean Gain on the Emergence of Cooperation in Unidirectional Pedestrian Flow

  王子洋, 马剑, 赵晖, 秦勇, 朱伟, 贾利民

  理论物理通讯. 2013, 59(03): 379-383.

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  When more than one pedestrian want to move to the same site, conflicts appear and thus the involved pedestrians play a motion game. In order to describe the emergence of cooperation during the conflict resolving process, an evolutionary cellular automation model is established considering the effect of aspiration and mean gain. In each game, pedestrian may be gentle cooperator or aggressive defector. We propose a set of win-stay-lose-shrift（WSLS）like rules for updating pedestrian's strategy. These rules prescribe that if the mean gain of current strategy between some given steps is larger than aspiration the strategy keeps, otherwise the strategy changes. The simulation results show that a high level aspiration will lead to more cooperation. With the increment of the statistic length, pedestrians will be more rational in decision making. It is also found that when the aspiration level is small enough and the statistic length is large enough all the pedestrian will turn to defectors. We use the prisoner's dilemma model to explain it. At last we discuss the effect of aspiration on fundamental diagram.
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  Editorial Announcement: Retraction of Commun. Theor. Phys. 57 (2012) 115–122

  ZHU Zhong-Yuan

  理论物理通讯. 2013, 59(03): 384-384.

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