2013年, 第59卷, 第04期　
刊出日期：2013-04-15

  

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  Hamiltonian Tri-Integrable Couplings of the AKNS Hierarchy

  MENG Jing-Han, MA Wen-Xiu

  理论物理通讯. 2013, 59(04): 385-392.

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  We propose a systematic approach for generating Hamiltonian tri-integrable couplings of soliton hierarchies. The resulting approach is based on semi-direct sums of matrix Lie algebras consisting of 4×4 block matrix Lie algebras. We apply the approach to the AKNS soliton hierarchy, and Hamiltonian structures of the obtained tri-integrable couplings are constructed by the variational identity.
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  Coupling Integrable Couplings of an Equation Hierarchy

  王惠, 夏铁成

  理论物理通讯. 2013, 59(04): 393-397.

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  Based on a kind of Lie algebra G proposed by Zhang, one isospectral problem is designed. Under the framework of zero curvature equation, a new kind of integrable coupling of an equation hierarchy is generated using the methods proposed by Ma and Gao. With the help of variational identity, we get the Hamiltonian structure of the hierarchy.
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  Quantum Teleportation via Completely Anisotropic Heisenberg Chain in Inhomogeneous Magnetic Field

  付成花, 胡占宁

  理论物理通讯. 2013, 59(04): 398-406.

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  The quantum teleportation with the entangled thermal state is investigated based on the completely anisotropic Heisenberg chain in the presence of the externally inhomogeneous magnetic field. The effects of the anisotropy and magnetic field for the quantum fidelity are studied in detail. The zero temperature limit and the features of the nonzero temperature for this nonclassical fidelity are obtained. We find that the quantum teleportation demands more stringent conditions than the thermal entanglement of the resource by investigating the threshold temperature of the thermal concurrence and the critical temperature of the maximal teleportation fidelity. The useful quantum teleportation should avoid the point of the phase transition of the system and the anisotropy of the chain and the external magnetic field can control the applicability of the resource in the quantum teleportation.
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  Quantum Correlations in Heisenberg XY Chain

  朱银燕, 张勇

  理论物理通讯. 2013, 59(04): 407-410.

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  Quantum correlations measured by quantum discord (QD), measurement-induced distance (MID), and geometric measure of quantum discord (GMQD) in two-qubit Heisenberg XY spin chain are investigated. The effects of DM interaction and anisotropic on the three correlations are considered. Characteristics of various correlation measures for the two-qubit states are compared. The increasing D_z increases QD, MID and GMQD monotonously while the increasing anisotropy both increases and decreases QD and GMQD. The three quantum correlations are always existent at very high temperature. MID is always larger than QD, but there is no definite ordering between QD and GMQD.
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  Large Detuning Limit for the Multipartite Systems Interacting with Electromagnetic Fields

  李虹轶, 吴春旺, 陈平形, 李承祖

  理论物理通讯. 2013, 59(04): 411-416.

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  We study the dynamics of the multipartite systems nonresonantly interacting with electromagnetic fields, focusing on the large detuning limit for the effective Hamiltonian. Due to the many-particle interference effects, the more rigorous large detuning condition for neglecting the rapidly oscillating terms for the effective Hamiltonian should be Δ>> N^1/2 g, instead of Δ>> g usually used in the literature even in the case of multipartite systems, with N the number of microparticles involved, g the coupling strength, Δ the detuning. This result is significant since merely the satisfaction of the original condition will result in the invalidity of the effective Hamiltonian and the errors of the parameters associated with the detuning in the multipartite case.
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  Ground States of Ultracold Spin-1 Atoms in a Deep Double-Well Optical Superlattice in a Weak Magnetic Field

  郑公平, 秦帅锋, 王守阳, 简闻天

  理论物理通讯. 2013, 59(04): 417-424.

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  The ground states of the ultracold spin-1 atoms trapped in a deep one-dimensional double-well optical superlattice in a weak magnetic field are obtained. It is shown that the ground-state diagrams of the reduced double-well model are remarkably different for the antiferromagnetic and ferromagnetic condensates. The transition between the singlet state and nematic state is observed for the antiferromagnetic interaction atoms, which can be realized by modulating the tunneling parameter or the quadratic Zeeman energy. An experiment to distinguish the different spin states is suggested.
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  Area and Entropy Spectrum of Gauss-Bonnet Gravity in de Sitter Space-Times for Black Hole Event Horizon

  陈强, 任继荣

  理论物理通讯. 2013, 59(04): 425-428.

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  In this paper, we use the modified Hod's treatment and the Kunstatter's method to study the horizon area spectrum and entropy spectrum in Gauss-Bonnet de-Sitter space-time, which is regarded as the natural generalization of Einstein gravity by including higher derivative correction terms to the original Einstein-Hilbert action. The horizon areas have some properties that are very different from the vacuum solutions obtained from the frame of Einstein gravity. With the new physical interpretation of quasinormal modes, the area/entropy spectrum for the event horizon for near-extremal Gauss-Bonnet de Sitter black holes are obtained. Meanwhile, we also extend the discussion of area/entropy quantization to the non-extremal black holes solutions.
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  Tracking Consensus for Second-Order Multi-Agent Systems with Nonlinear Dynamics in Noisy Environments

  路晓庆, 陈士华

  理论物理通讯. 2013, 59(04): 429-438.

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  This paper investigates the leader-following tracking consensus problem for second-order multi-agent systems with time delays and nonlinear dynamics in noisy environments on the conditions of fixed and switching directed topologies. Based on a novel velocity decomposition technique and stochastic analysis, a measurement-based distributed tracking control protocol is proposed, under which all agents can track the leader in mean square. Simulation results are also given to illustrate the effectiveness of the proposed protocol.
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  General Formalism for the BRST Symmetry

  Suhail Ahmad

  理论物理通讯. 2013, 59(04): 439-442.

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  In this paper we will discuss Faddeev-Popov method for gauge theories with a general form of gauge symmetry in an abstract way. We will then develope a general formalism for dealing with the BRST symmetry. This formalism will make it possible to analyse the BRST symmetry for any theory.
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  Flavor Changing Top Quark Decay and Bottom-Strange Production in the Littlest Higgs Model with T-parity

  侯洪生, 孙昊, 周雅瑾

  理论物理通讯. 2013, 59(04): 443-450.

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  Flavor changing effects on the processes t→ch, e⁺e^-→bs, e⁺e^-→bsh and pp→bs in the LHT model are investigated in this paper. We calculate the one-loop level contributions from the T-parity odd mirror fermions and gauge bosons. The results show that the top quark rare decay t→ch in the LHT model can be significantly enhanced relative to that in the SM. The bs production at linear colliders in the LHT model can enhance the SM cross section a lot and reach 0.1 fb in some parameter space allowed in the experiment. But the heavy gauge boson and mirror fermion loops have small contribution to the processes pp→bs and e⁺e^-→bsh. So the LHT effect on e⁺e^-→bs might be detected at future linear colliders, while it is too small to be seen for the e⁺e^-→bsh and pp→bs processes at future linear colliders and LHC.
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  Analysis of the Light-Flavor Scalar and Axial-Vector Diquark States with QCD Sum Rules

  王志刚

  理论物理通讯. 2013, 59(04): 451-456.

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  In this article, we study the light-flavor scalar and axial-vector diquark states in the vacuum and in the nuclear matter using the QCD sum rules in a systematic way, and make reasonable predictions for their masses in the vacuum and in the nuclear matter.
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  B_s→f₀(980) Transition Form Factors Within the k_T Factorization Approach

  曾代敏, 方祯云

  理论物理通讯. 2013, 59(04): 457-461.

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  In the paper, we apply the k_T factorization approach to deal with the B_s→f₀(980) transition form factors in the large recoil regions, i.e. the small q² regions. For the purpose, we adopt the B-meson wave-functions Ψ_B, Ψ_B and δ that include the three-Fock states contributions to do our discussion. Although the scalar meson f₀(980) is widely perceived as the 4-quark bound state (scenario 2), but the distribution amplitudes of 4-quark states are still unknown to us, so we adopt 2-quark model (scenario 1) for scalar meson f₀(980) in our discussion. By varying the B-meson wave-function parameters within their reasonable regions, we obtain F₀(0)=F₊(0)=0.20±0.02, F_T(0)=0.24±0.02. Our present results for these form factors are consistent with the light-cone sum rule results obtained in the literature.
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  Longitudinal Structure Function F_L from Charm Structure Function F₂^c

  B. Rezaei, G.R. Boroun

  理论物理通讯. 2013, 59(04): 462-466.

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  We predict the effect of the charm structure function on the longitudinal structure function at small x. In NLO analysis we find that the hard Pomeron behavior gives a good description of F_L and F_k^c (k=2,L) at small x values. We conclude that a direct relation between F_L ∝ F₂^c would provide useful information on how to measure longitudinal structure function at high Q₂ values. Having checked that this model gives a good description of the data, when compared with other models.
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  θ₁₃ and the Higgs Mass from High Scale Supersymmetry

  刘纯, 赵振华

  理论物理通讯. 2013, 59(04): 467-471.

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  In the framework in which supersymmetry is used for understanding fermion masses rather than stabilizing the electroweak scale, we elaborate on the phenomenological analysis for the neutrino physics. A relatively large sinθ₁₃  0.13 is naturally obtained. The model further predicts vanishingly small CP violation in neutrino oscillations. While the high scale supersymmetry generically results in a Higgs mass of about 141 GeV, our model reduces this mass to 126 GeV via introducing SU(2)_L triplet fields which make the electroweak vacuum metastable (with a safe lifetime) and also contribute to neutrino masses.
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  Search for Majorana Neutrino Signal in B_c Meson Rare Decay

  鲍守山, 李洪蕾, 司宗国, 杨一玻

  理论物理通讯. 2013, 59(04): 472-478.

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  We study the B_c meson rare decay in order to search for the Majorana neutrino signal. It is found that the corresponding decay rate is sensitive to the Majorana neutrino mass and mixing angles. The signal of B_c^±→l₁^±l₂^±M induced by the Majorana neutrino within the mass region m_π < m_n < m_B may be observed at LHCb.
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  Nonplanar Electrostatic Solitary Waves in a Relativistic Degenerate Dense Plasma

  Ata-ur-Rahman, A. Mushtaq, S. Ali, A. Qamar

  理论物理通讯. 2013, 59(04): 479-483.

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  By employing the reductive perturbation technique, the propagation of cylindrical and spherical ion acoustic solitary waves is studied in an unmagnetized dense relativistic plasma, consisting of relativistically degenerate electrons and cold fluid ions. A modified Korteweg-de-Vries equation is derived and its numerical solutions have been analyzed to identify the basic features of electrostatic solitary structures that may form in such a degenerate Fermi plasma. Different degrees of relativistic electron degeneracy are discussed and compared. It is found that increasing number density leads to decrease the amplitude the width of the ion acoustic solitary wave in both the cylindrical and spherical geometries. The relevance of the work to the compact astrophysical objects, particularly white dwarfs is pointed out.
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  Modified Bubble Core Fields and Bubble Shape in Laser Driven Plasma

  吴海城, 谢柏松

  理论物理通讯. 2013, 59(04): 484-488.

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  Bubble core fields as well bubble shape modification due to the nondepleted electrons inside the bubble is investigated theoretically. It is found that the slope of transverse fields are reduced significantly, however, the slope of longitudinal electric field, which plays a key role on electrons acceleration in bubble, changes little. Moreover a modified longitudinal compressed bubble shape leads to a shorter dephasing distance which makes the electrons acceleration energy reduced to some extent. As a comparison we perform particle-in-cell simulations whose results are consistent with that of our theoretical consideration.
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  Topological Insulators in α-Graphyne

  王国祥, 侯净敏

  理论物理通讯. 2013, 59(04): 489-493.

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  In this paper, we investigate topological phases of α-graphyne with tight-binding method. By calculating the topological invariant Z₂ and the edge states, we identify topological insulators. We present the phase diagrams of α-graphyne with different filling fractions as a function of spin-orbit interaction and the nearest-neighbor hopping energy. We find there exist topological insulators in α-graphyne. We analyze and discuss the characteristics of topological phases of α-graphyne.
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  Effect of Transverse Correlation Function on the Thermodynamic Quantities of Ferromagnetic Systems

  秦伟, 王怀玉, 龙桂鲁

  理论物理通讯. 2013, 59(04): 494-502.

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  The effect of transverse correlation between spins on the thermodynamic properties of ferromagnetic systems is investigated in details. Qualitatively, at finite temperature the transverse correlation reflects the short-range interaction between spins, so that lowers the internal energy and consequently raises the free energy. It also means the introduction of some ordering, and hence lowers the entropy. It is depressed by the field which forces the spins to turn to the field direction, so that it decreases with the field when temperature is fixed. The low-temperature expansion of the energy shows that the inclusion of the transverse correlation at least partly considers the interaction between spin waves.
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  Stationary Response of Lotka-Volterra System with Real Noises

  戚鲁媛, 徐伟, 高维廷

  理论物理通讯. 2013, 59(04): 503-509.

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  A stochastic version of Lotka-Volterra model subjected to real noises is proposed and investigated. The approximate stationary probability densities for both predator and prey are obtained analytically. The original system is firstly transformed to a pair of Itô stochastic differential equations. The Itô formula is then carried out to obtain the Itô stochastic differential equation for the period orbit function. The orbit function is considered as slowly varying process under reasonable assumptions. By applying the stochastic averaging method to the orbit function in one period, the averaged Itô stochastic differential equation of the motion orbit and the corresponding Fokker-Planck equation are derived. The probability density functions of the two species are thus formulated. Finally, a classical real noise model is given as an example to show the proposed approximate method. The accuracy of the proposed procedure is verified by Monte Carlo simulation.
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  Rumor Spreading Model with Trust Mechanism in Complex Social Networks

  王亚奇, 杨晓元, 韩益亮, 王绪安

  理论物理通讯. 2013, 59(04): 510-516.

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  In this paper, to study rumor spreading, we propose a novel susceptible-infected-removed (SIR) model by introducing the trust mechanism. We derive mean-field equations that describe the dynamics of the SIR model on homogeneous networks and inhomogeneous networks. Then a steady-state analysis is conducted to investigate the critical threshold and the final size of the rumor spreading. We show that the introduction of trust mechanism reduces the final rumor size and the velocity of rumor spreading, but increases the critical thresholds on both networks. Moreover, the trust mechanism not only greatly reduces the maximum rumor influence, but also postpones the rumor terminal time, which provides us with more time to take measures to control the rumor spreading. The theoretical results are confirmed by sufficient numerical simulations.
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  Massive Scalar Field Evolution in the Dyadosphere Spacetime of Charged Black Hole

  王春艳, 高亚军

  理论物理通讯. 2013, 59(04): 517-520.

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  Scalar field quasinormal modes in the dyadosphere spacetime of charged black hole are studied by using the third-order WKB approximation. From numerical results obtained, we find that the scalar field mass u plays an important role in studying the quasinormal frequencies. With the scalar field mass increases, the real parts increase and the magnitudes of the imaginary parts decrease. Particulary, these change are almost linearly.