2015年, 第63卷, 第02期　
刊出日期：2015-02-01

  

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  Nonlocal Symmetry Reductions, CTE Method and Exact Solutions for Higher-Order KdV Equation

  任博, 刘希忠, 刘萍

  理论物理通讯. 2015, 63(02): 125-128.

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  The nonlocal symmetries for the higher-order KdV equation are obtained with the truncated Painlevé method. The nonlocal symmetries can be localized to the Lie point symmetries by introducing suitable prolonged systems. The finite symmetry transformations and similarity reductions for the prolonged systems are computed. Moreover, the consistent tanh expansion (CTE) method is applied to the higher-order KdV equation. These methods lead to some novel exact solutions of the higher-order KdV system.
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  The Categorification of Fermions

  王娜, 王蕊, 王志玺, 吴可, 杨洁, 杨紫峰

  理论物理通讯. 2015, 63(02): 129-135.

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  In this paper, we lift Fermions to functors acting on some homotopy category by the Boson-Fermion correspondence and get the categorified relations of Fermions. In this way, both the categorified Bosons and the categorified Fermions can be viewed as functors on the same category. We also give actions of these functors on the charged Young diagrams (or equivalently, Maya diagrams), so that the classical theory of Boson-Fermion correspondence is very well recovered as a result of such a categorification.
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  Symmetry Reduction of (2+1)-Dimensional Lax-Kadomtsev-Petviashvili Equation

  胡恒春, 王竞博, 朱海东

  理论物理通讯. 2015, 63(02): 136-140.

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  The Lax-Kadomtsev-Petviashvili equation is derived from the Lax fifth order equation, which is an important mathematical model in fluid physics and quantum field theory. Symmetry reductions of the Lax-Kadomtsev-Petviashvili equation are studied by the means of the Clarkson-Kruskal direct method and the corresponding reduction equations are solved directly with arbitrary constants and functions.
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  Quantum Violations of N-Qubit Svetlichny's Inequalities are Tightly Bound by the Exclusivity Principle

  向阳

  理论物理通讯. 2015, 63(02): 141-144.

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  We first present, by using exclusivity principle, a brief proof of the complementarity principle: the sum of squared expectation values of dichotomic (±1) mutually complementary observables can not be greater than 1. Then we prove that the complementarity principle yields tight quantum bounds of violations of N-qubit Svetlichny's inequalities. This result not only demonstrates that exclusivity principle can give tight quantum bound for certain type of genuine multipartite correlations, but also illustrates the subtle relationship between quantum complementarity and quantum genuine multipartite correlations.
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  Zitterbewegung in Bogoliubov's System

  李艳, 苏洪轶, 张福林, 陈景灵

  理论物理通讯. 2015, 63(02): 145-148.

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  We show that Bogoliubov's quasiparticle in superfluid ³He-B undergoes the Zitterbewegung, as a free relativistic Dirac's electron does. The expectation value of position, as well as spin, of the quasiparticle is obtained and compared with that of the Dirac's electron. In particular, the Zitterbewegung of Bogoliubov's quasiparticle has a frequency approximately 10⁵ lower than that of an electron, rendering a more promising experimental observation.
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  Quantum State Preparation and Protection by Measurement-Based Feedback Control Against Decoherence

  闫妍, 邹健, 王璐, 徐宝明, 王朝全, 邵彬

  理论物理通讯. 2015, 63(02): 149-158.

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  We consider an open quantum system subjected to a noise channel under measurement-based feedback control and two prototypical classes of decoherence channels are considered: phase damping and generalized amplitude damping. Based on quantum trajectory theory, we obtain an extended master equation for the dynamics of the reduced system in the presence of feedback control. For a qubit system we analytically solve this master equation and obtain the solution of the state vector dynamics. Then we propose an effective feedback control scheme for preparing an arbitrary quantum pure state. We also study how to protect two nonorthogonal states effectively, and find that projective measurement with unbiased basis is not optimal for this task, while weak measurement with biased basis could realize the best protection of two nonorthogonal states. Furthermore, the inefficiencies in the feedback process are also discussed.
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  The Effect of Magnetic Field on an Asymmetrical Gaussian Potential Quantum Well Qubit

  蔡春雨, 赵翠兰, 肖景林

  理论物理通讯. 2015, 63(02): 159-162.

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  Under the influence of an applied magnetic field (MF), the eigenenergies and the eigenfunctions of the ground and the first excited states (GFES) are obtained by using a variational method of the Pekar type (VMPT) in a strong electron-LO-phonon coupling asymmetrical Gaussian potential quantum well (AGPQW). This AGPQW system may be employed as a two-level qubit. The numerical results have indicated (i) that when the electron situates in the superposition state of the GFES, we obtain the time evolution and the coordinate change of the electron probability density in the AGPQW, (ii) that due to the presence of the asymmetrical potential in the growth direction of the AGPQW, the probability density shows double-peak configuration, whereas there is only one peak if the confinement is a two dimensional symmetric one in the xy plane of the AGPQW, (iii) that the oscillatory period is a decreasing function of the cyclotron frequency of the MF, the height of the AGPQW and the polaron radius, (iv) and that as the range of the confinement potential (RCP) decreases the oscillatory period will decrease firstly and then increase and it will take a minimum when R=-0.234 nm.
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  A Family of Degenerate Codes for Depolarizing Channels

  陈小余, 赵蒋军, 王婷婷, 寿超骏

  理论物理通讯. 2015, 63(02): 163-167.

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  Quantum degenerate code may improve the hashing bound of quantum capacity. We propose a family of quantum degenerate codes derived from two-colorable graphs. The coherent information of the codes is analytically obtained as a function of the channel noise for the depolarizing channel. We find a new code which has a higher noise threshold than that of the repetition code.
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  Phase Space Analysis and Anisotropic Universe Model in f(T) Gravity

  M. Sharif, Saima Jabbar

  理论物理通讯. 2015, 63(02): 168-180.

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  In this paper, we study the stability of locally rotationally symmetric (LRS) Bianchi Ⅰ universe model in f(T) gravity through phase space analysis. We assume that the f(T) gravity can be treated as effective dark energy behaving like perfect fluid, and suggest that there are interactions between pressureless matter as well as dark energy. We construct the corresponding autonomous system of equations to check the stability of the model for non phantom, vacuum and phantom phases. It is concluded that critical points remain more stable in phantom phase as compared to non phantom and vacuum cases. Finally, we discuss the cosmological behavior of the model through some cosmological parameters.
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  Correlation Functions of an Autonomous Stochastic System with Nonlinear Time Delays

  朱平, 朱毅杰

  理论物理通讯. 2015, 63(02): 181-187.

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  The auto-correlation function and the cross-correlation of an autonomous stochastic system with nonlinear time-delayed feedback are investigated by using the stochastic simulation method. There are prominent differences between the roles of quadratic time-delayed feedback and cubic time-delayed feedback on the correlations of an autonomous stochastic system. Under quadratic time-delayed feedback, the nonlinear time delay fails to improve the noisy state of the autonomous stochastic system, the auto-correlation decreases monotonously to zero, and the cross-correlation increases monotonously to zero with the decay time. Under cubic time-delayed feedback, the nonlinear time delay can improve the noisy state of the autonomous stochastic system; the auto-correlation and the cross-correlation show periodical oscillation and attenuation, finally tending to zero with the decay time. Comparing the correlations of the system between with nonlinear time-delayed feedback and linear time-delayed feedback, we find that nonlinear time-delayed feedback lowers the correlation strength of the autonomous stochastic system.
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  Radiative Corrections to e⁺e^-→Zh at Future Higgs Factory in the Minimal Dilaton Model

  衡朝霞, 李东玮, 周海静

  理论物理通讯. 2015, 63(02): 188-194.

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  The minimal dilaton model (MDM) extends the Standard Model by one singlet scalar called dilaton and one top quark partner called t'. In this work we investigate the t'-induced radiative correction to the Higgs-strahlung production process e⁺e^-→Zh at future Higgs factory. We first present the analytical calculations in detail and show how to handle the ultraviolet divergence. Then we calculate the correction numerically by considering the constraints from precision electroweak data. We find that, for sin θ_L=0.2 and m_t'=1200 GeV, the correction is 0.26% and 2.1% for √S_e+e=240 GeV, 1 TeV respectively, and a larger value can be achieved as sin θ_L increases.
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  A Classification of Long-Range Interactions between Two Stacks of p & p'-Branes

  欧阳君, 吴超

  理论物理通讯. 2015, 63(02): 195-208.

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  We generalize the computations of the long-range interactions between two parallel stacks of branes to various cases when two stacks of branes are not placed parallel to each other. We classify the nature of interaction (repulsive or attractive) for each special case and this classification can be used to justify the nature of long-range interaction between two complicated brane systems such as brane bound states. We will provide explicit examples in this paper to demonstrate this.
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  Temperature Dependence of Decuplet Baryon Masses from Thermal QCD Sum Rules

  徐永江, 刘永录, 黄明球

  理论物理通讯. 2015, 63(02): 209-214.

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  In the present work, the masses of the decuplet baryons at finite temperature are investigated using thermal QCD sum rules. Making use of the quark propagator at finite temperature, we calculate the spectral functions to T⁸ order, and find that there are no contributions to the spectral functions at T⁸ order and the temperature corrections mainly come from that containing T⁴ ones. The calculations show very little temperature dependence of the masses below T=0.11 GeV. While above that value, the masses decrease with increasing temperature. The results indicate that the hadron-quark phase transition temperature may be T_c≥0.11 GeV for the decuplet bayons.
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  Nucleon Resonances in the π^-p→K⁰Λ Reaction near Threshold

  吴承祖, 吕齐放, 谢聚军, 陈旭荣

  理论物理通讯. 2015, 63(02): 215-221.

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  We investigate the two-body reaction π^-p→K⁰Λ within the effective Lagrangian approach and the isobar model. In addition to the "background" contributions from t-channel K^* exchange, u-channel Σ(1192) and Σ^*(1385) exchanges, and s-channel nucleon pole terms, the contributions from the nucleon resonances N^*(1535), N^*(1650), and N^*(1720) are investigated. It is shown that the inclusion of these nucleon resonances contributions leads to a good descrip-tion of the experimental total and differential cross sections data at low energy region. The s-channel N^*(1535), N^*(1650), and N^*(1720) resonances and the t-channel K^* exchange give the dominant contributions below W=1.76 GeV, while the s-channel nucleon pole, u-channel Σ(1192) and Σ^*(1385) exchanges give the minor contributions.
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  Fitting Single Particle Energies in sdgh Major Shell

  Erdal Dikmen, Oğuz Öztürk, Yavuz Cengiz

  理论物理通讯. 2015, 63(02): 222-228.

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  We have performed two kinds of non-linear fitting procedures to the single-particle energies in the sdgh major shell to obtain better shell model results. The low-lying energy eigenvalues of the light Sn isotopes with A=103-110 in the sdgh-shell are calculated in the framework of the nuclear shell model by using CD-Bonn two-body effective nucleon-nucleon interaction. The obtained energy eigenvalues are fitted to the corresponding experimental values by using two different non-linear fitting procedures, i.e., downhill simplex method and clonal selection method. The unknown single-particle energies of the states 2s_1/2, 1d_3/2, and 0h_11/2 are used in the fitting methods to obtain better spectra of the ^{104,106,108,110}Sn isotopes. We compare the energy spectra of the ^{104,106,108,110}Sn and ^{103,105,107,109}Sn isotopes with/without a nonlinear fit to the experimental results.
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  Electromagnetically Induced Transparency and Absorption of A Monochromatic Light Controlled by a Radio Frequency Field

  蔡勋明

  理论物理通讯. 2015, 63(02): 229-235.

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  Electromagnetically induced transparency and absorption of a monochromatic light controlled by a radio frequency field in the cold multi-Zeeman-sublevel atoms are theoretically investigated. These Zeeman sublevels are coupled by a radio frequency (RF) field. Both electromagnetically induced transparency and electromagnetically induced absorption can be obtained by tuning the frequency of RF field for both the linear polarization and elliptical polarization monochromatic lights. When the transfer of coherence via spontaneous emission from the excited state to the ground state is considered, electromagnetically induced absorption can be changed into electromagnetically induced transparency with the change of intensity of radio field. The transparency windows controlled by the RF field can have potential applications in the magnetic-field measurement and quantum information processing.
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  Optimization of the Doped Ablator Layers for the Plastic Ignition Capsule

  谷建法, 戴振生, 李永升, 宋鹏, 叶文华, 邹士阳, 郑无敌, 朱少平

  理论物理通讯. 2015, 63(02): 236-242.

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  The paper investigates theoretically the optimization of the doped ablator layers for the plastic ignition capsule. The high-resolved one-dimensional implosion simulations show that the inner pure CH layer of the Si-doped design is excessively preheated by the hard x-ray, leading to the unstable ablator-fuel interface compared to the Ge-doped capsule. This is because that the Si K-shell absorption edge (1.8 keV) is higher than the Ge L-edge (1.3 keV), and Si dopant makes more hard x-ray penetrate through the doped ablator layers to preheat the inner pure CH layer. So an optimization of the doped ablator layers (called "Si/Ge capsule") is performed: an Si-doped CH layer is placed next to the outer pure CH layer to keep the high implosion velocity; next to the Si-doped layer is a thin Ge-doped layer, in order to absorb the hard x-ray and protect the inner undoped CH-layer from excessively preheating. The simulations show that the Si/Ge capsule can effectively improve hydrodynamic stability at the ablator-fuel interface while keeping the high implosion velocity.
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  Cylindrical and Spherical Electron-Acoustic Shock Waves in Electron-Positron-Ion Plasmas with Nonextensive Electrons and Positrons

  A. Rafat, M. M. Rahman, M. S. Alam, A. A. Mamun

  理论物理通讯. 2015, 63(02): 243-248.

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  Electron-acoustic shock waves (EASWs) in an unmagnetized four-component plasma (containing hot electrons and positrons following the q-nonextensive distribution, cold mobile viscous electron fluid, and immobile positive ions) are studied in nonplanar (cylindrical and spherical) geometry. With the help of the reductive perturbation method, the modified Burgers equation is derived. Analytically, the effects of nonplanar geometry, nonextensivity, relative number density and temperature ratios, and cold electron kinematic viscosity on the basic properties (viz. amplitude, width, speed, etc.) of EASWs are discussed. It is examined that the EASWs in nonplanar geometry significantly differ from those in planar geometry. The results of this investigation can be helpful in understanding the nonlinear features of EASWs in various astrophysical plasmas.
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  Can Nano-Particle Melt below the Melting Temperature of Its Free Surface Partner?

  眭晓红, 王宗国, 康凯, 覃绍京, 王垂林

  理论物理通讯. 2015, 63(02): 249-254.

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  The phonon thermal contribution to the melting temperature of nano-particles is inspected. The discrete summation of phonon states and its corresponding integration form as an approximation for a nano-particle or for a bulk system have been analyzed. The discrete phonon energy levels of pure size effect and the wave-vector shifts of boundary conditions are investigated in detail. Unlike in macroscopic thermodynamics, the integration volume of zero-mode of phonon for a nano-particle is not zero, and it plays an important role in pure size effect and boundary condition effect. We find that a nano-particle will have a rising melting temperature due to purely finite size effect; a lower melting temperature bound exists for a nano-particle in various environments, and the melting temperature of a nano-particle with free boundary condition reaches this lower bound. We suggest an easy procedure to estimation the melting temperature, in which the zero-mode contribution will be excluded, and only several bulk quantities will be used as input. We would like to emphasize that the quantum effect of discrete energy levels in nano-particles, which is not present in early thermodynamic studies on finite size corrections to melting temperature in small systems, should be included in future researches.
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  Quasi-Conical Quantum Dot: Electron States and Quantum Transitions

  Eduard M. Kazaryan, Lyudvig S. Petrosyan, Vanik A. Shahnazaryan, Hayk A. Sarkisyan

  理论物理通讯. 2015, 63(02): 255-260.

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  The exactly solvable model of quasi-conical quantum dot, having a form of spherical sector, is proposed. Due to the specific symmetry of the problem the separation of variables in spherical coordinates is possible in the one-electron Schrodinger equation. Analytical expressions for wave function and energy spectrum are obtained. It is shown that at small values of the stretch angle of spherical sector the problem is reduced to the conical QD problem. The comparison with previously performed works shows good agreement of results. As an application of the obtained results, the quantum transitions in the system are considered.
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  Nagaoka Ferromagnetism in Two-Band Hubbard Model

  张德平, 田光善, 林海青

  理论物理通讯. 2015, 63(02): 261-270.

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  In the present paper, we investigate the existence of ferromagnetism in a two-band Hubbard model, by applying a recently-introduced method by us to study ferromagnetism in metallic clusters. We prove rigorously that the ground state of this model is ferromagnetic if the intra-orbital Coulomb repulsion between electrons is infinitely strong and only one hole exists in the system. Our theorem improves a previous result. Furthermore, our method can also be applied to deal with the case of multiple holes.