2012年, 第57卷, 第06期　
刊出日期：2012-06-15

  

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  The Qiao--Liu Equation with Self-Consistent Sources and Its Solutions

  姚玉芹, 黄晔辉, 曾云波

  理论物理通讯. 2012, 57(06): 909-913.

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  The Qiao--Liu equation with self-consistent sources (QLESCS) and its Lax representation are derived. A reciprocal transformation for the QLESCS is given. By making use of the reciprocal transformation and the solutions of the mKdV equation with self-consistent sources (mKdVSCS), the solutions of the QLESCS are presented.
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  Oscillatory and Asymptotic Behavior of a Second-Order Nonlinear Functional Differential Equations

  张全信, 高丽, 王少英

  理论物理通讯. 2012, 57(06): 914-922.

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  This paper is concerned with oscillatory and asymptotic behavior of solutions of a class of second order nonlinear functional differential equations. By using the generalized Riccati transformation and the integral averaging technique, new oscillation criteria and asymptotic behavior are obtained for all solutions of the equation. Our results generalize and improve some known theorems.
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  Rational Solutions with Non-zero Asymptotics of the Modified Korteweg-de Vries Equation

  孙莹莹, 张大军

  理论物理通讯. 2012, 57(06): 923-929.

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  Using the relation between the mKdV equation and the KdV-mKdV equation, we derive non-singular rational solutions for the mKdV equation. The solutions are given in terms of Wronskians. Dynamics of some solutions is investigated by means of asymptotic analysis. Wave trajectories of high order rational solutions are asymptotically governed by cubic curves.
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  One Electron Atom in Special Relativity with de Sitter Space-Time Symmetry

  闫沐霖

  理论物理通讯. 2012, 57(06): 930-952.

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  The de Sitter invariant Special Relativity (dS-SR) is SR with constant curvature, and a natural extension of usual Einstein SR (E-SR). In this paper, we solve the dS-SR Dirac equation of Hydrogen by means of the adiabatic approach and the quasi-stationary perturbation calculations of QM. Hydrogen atom is located in the light cone of the Universe. FRW metric and ΛCDM cosmological model are used to discuss this issue. To the atom, effects of de Sitter space-time geometry described by Beltrami metric are taken into account. The dS-SR Dirac equation turns out to be a time dependent quantum Hamiltonian system. We reveal that: (i) The fundamental physics constants m_e,h,e variate adiabatically along with cosmologic time in dS-SR QM framework. But the fine-structure constant α≡ e²/(hc) keeps to be invariant; (ii) (2s^1/2-2p^1/2)-splitting due to dS-SR QM effects: By means of perturbation theory, that splitting Δ E(z) are calculated analytically, which belongs to O(1/R²)-physics of dS-SR QM. Numerically, we find that when |R|～{10³Gly, 10⁴Gly, 10⁵Gly}, and z～{1,or 2}, the Δ E(z)>>1 (Lamb shift). This indicates that for these cases the hyperfine structure effects due to QED could be ignored, and the dS-SR fine structure effects are dominant. This effect could be used to determine the universal constant R in dS-SR, and be thought as a new physics beyond E-SR.
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  Bargmann Symmetry Constraint for a Family of Liouville Integrable Differential-Difference Equations

  徐西祥

  理论物理通讯. 2012, 57(06): 953-960.

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  A family of integrable differential-difference equations is derived from a new matrix spectral problem. The Hamiltonian forms of obtained differential-difference equations are constructed. The Liouville integrability for the obtained integrable family is proved. Then, Bargmann symmetry constraint of the obtained integrable family is presented by binary nonliearization method of Lax pairs and adjoint Lax pairs. Under this Bargmann symmetry constraints, an integrable symplectic map and a sequences of completely integrable finite-dimensional Hamiltonian systems in Liouville sense are worked out, and every integrable differential-difference equations in the obtained family is factored by the integrable symplectic map and a completely integrable finite-dimensional Hamiltonian system.
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  Nonlinear Super Integrable Couplings of Super Dirac Hierarchy and Its Super Hamiltonian Structures

  尤福财

  理论物理通讯. 2012, 57(06): 961-966.

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  We construct nonlinear super integrable couplings of the super integrable Dirac hierarchy based on an enlarged matrix Lie superalgebra. Then its super Hamiltonian structure is furnished by super trace identity. As its reduction, we gain the nonlinear integrable couplings of the classical integrable Dirac hierarchy.
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  Quantum Measurement and Extended Feynman Path Integral

  文伟, 白彦魁

  理论物理通讯. 2012, 57(06): 967-982.

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  Quantum measurement problem has existed many years and inspired a large of literature in both physics and philosophy, but there is still no conclusion and consensus on it. We show it can be subsumed into the quantum theory if we extend the Feynman path integral by considering the relativistic effect of Feynman paths. According to this extended theory, we deduce not only the Klein--Gordon equation, but also the wave-function-collapse equation. It is shown that the stochastic and instantaneous collapse of the quantum measurement is due to the “potential noise” of the apparatus or environment and “inner correlation” of wave function respectively. Therefore, the definite-status of the macroscopic matter is due to itself and this does not disobey the quantum mechanics. This work will give a new recognition for the measurement problem.
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  Dynamics of Entanglement for a Two-Parameter Class of States in a Qubit-Qutrit System

  魏海瑞, 任宝藏, 李涛, 华明, 邓富国

  理论物理通讯. 2012, 57(06): 983-990.

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  We investigate the dynamics of entanglement for a two-parameter class of states in a hybrid qubit-qutrit system under the influence of various dissipative channels. Our results show that entanglement sudden death (ESD) is a general phenomenon and it usually takes place in a qubit-qutrit system interacting with various noisy channels, not only the case with dephasing and depolarizing channels observed by others. ESD can only be avoided for some initially entangled states under some particular noisy channels. Moreover, the environment affects the entanglement and the coherence of the system in very different ways.
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  Optimal Phase-Covariant Cloning in 3 Dimensions

  张文海, 余龙宝, 曹卓良, 叶柳

  理论物理通讯. 2012, 57(06): 991-994.

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  In this paper, we present the explicit transformations of the optimal 1 → 3, 4, 5 phase-covariant cloning in 3 dimensions. The cloning fidelities are covered by the theoretical bounds of the optimal 1 → 3k, 3k + 1, 3k + 2 phase-covariant cloning of qutrits, where k ≥ 1 is the integral [Phys. Rev. A 67 (2003) 042306].
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  Quantum Information Splitting of an Arbitrary Three-Atom State by Using W-class States in Cavity QED

  李渊华, 聂义友

  理论物理通讯. 2012, 57(06): 995-998.

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  We demonstrate that four sets of W-class states can be used to realize the deterministic quantum information splitting of an arbitrary three-atom state in cavity QED. The scheme does not involve Bell-state measurement and is insensitive to both the cavity decay and the thermal field.
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  Quantum Phase Transition and Thermal Entanglement in the Isotropic XXX Model

  马富武, 孔祥木

  理论物理通讯. 2012, 57(06): 999-1006.

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  We investigate the quantum phase transition (QPT) and the pairwise thermal entanglement in the three-qubit Heisenberg XXX chain with Dzyaloshinskii--Moriya (DM) interaction under a magnetic field. The ground states of the system exist crossing points, which shows that the system exhibits a QPT. At a given temperature, the entanglement undergoes two sudden changes (platform-like behavior) as the DM interaction or external magnetic field increases. This special property can be used as the entanglement switch, which is also influenced by the temperature. We can modulate the DM interaction or external magnetic field to control the entanglement switch.
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  Nonlinear Ramsey Interferometry of Fermi Superfluid Gases in a Double-Well Potential

  蒙红娟, 苟学强, 王文元, 杨阳, 段文山

  理论物理通讯. 2012, 57(06): 1007-1011.

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  The nonlinear Ramsey interferometry of Fermi superfluid gases in a double-well potential is investigated in this paper. We found that the frequency of the Ramsey fringes exactly reflects the strength of nonlinearity, or the scattering length of the Fermi superfluid gases. The cases of sudden limit, the adiabatic limit and the general case are studied. The analytical result is in good agreement with the numerical ones. The adiabatic condition is proposed. In general situation, the zero-frequency point emerge. Finally the possible applications of the theory are discussed.
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  Lie Algebras and Integrable Systems

  张玉峰, 梅建琴

  理论物理通讯. 2012, 57(06): 1012-1022.

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  A 3? 3 matrix Lie algebra is first introduced, its subalgebras and the generated Lie algebras are obtained, respectively. Applications of a few Lie subalgebras give rise to two integrable nonlinear hierarchies of evolution equations from their reductions we obtain the nonlinear Schrödinger equations, the mKdV equations, the Broer-Kaup (BK) equation and its generalized equation, etc. The linear and nonlinear integrable couplings of one integrable hierarchy presented in the paper are worked out by casting a 3? 3 Lie subalgebra into a 2? 2 matrix Lie algebra. Finally, we discuss the elliptic variable solutions of a generalized BK equation.
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  Oscillatory Dynamics and Oscillation Death in Complex Networks Consisting of Both Excitatory and Inhibitory Nodes

  张立升, 廖旭红, 弭元元, 谷伟凤, 胡岗

  理论物理通讯. 2012, 57(06): 1023-1032.

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  In neural networks, both excitatory and inhibitory cells play important roles in determining the functions of systems. Various dynamical networks have been proposed as artificial neural networks to study the properties of biological systems where the influences of excitatory nodes have been extensively investigated while those of inhibitory nodes have been studied much less. In this paper, we consider a model of oscillatory networks of excitable Boolean maps consisting of both excitatory and inhibitory nodes, focusing on the roles of inhibitory nodes. We find that inhibitory nodes in sparse networks (small average connection degree) play decisive roles in weakening oscillations, and oscillation death occurs after continual weakening of oscillation for sufficiently high inhibitory node density. In the sharp contrast, increasing inhibitory nodes in dense networks may result in the increase of oscillation amplitude and sudden oscillation death at much lower inhibitory node density and the nearly highest excitation activities. Mechanism under these peculiar behaviors of dense networks is explained by the competition of the duplex effects of inhibitory nodes.
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  Can X(3872) be a J^P=2^- Tetraquark State?

  崔春雨, 刘永录, 张国斌, 黄明球

  理论物理通讯. 2012, 57(06): 1033-1036.

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  In this article, we test the nature of X(3872), which is assumed to be a P-wave [cq]-scalar-diquark [cq]-axial-vector-antidiquark tetraquark state with J^P=2^-. The interpolating current representing the J^P=2^- state is proposed. Technically, contributions of the operators up to dimension six are included in the operator product expansion. The mass obtained for such state is m_2-=(4.38? 0.15) GeV. We conclude that it is impossible to describe the X(3872) structure as J^P=2^- tetraquark state.
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  Color-Flavor Locked Strangelets in a New Quark Model with Linear Confinement and Coulomb-Type Interactions

  陈世武, 彭光雄

  理论物理通讯. 2012, 57(06): 1037-1042.

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  The color-flavor locked (CFL) strangelets have been investigated in a new quark model with linear confinement and one-gluon-exchange interactions. Considering Coulomb energy, we have studied the properties of three kinds of CFL strangelets, namely, positively charged, negatively charged and nearly neutral CFL strangelets. It is found that the one-gluon-exchange effect lowers the energy of a strangelet considerably and thus makes it much more stable than without considering the effect. The charge of a positive strangelet is larger than 0.15A^2/3 with A being the baryon number, but smaller than that in bag model. The charge of a negatively charged or nearly neutral CFL strangelet is nearly proportional to A^1/3.
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  Net-Baryon and Net-Kaon Rapidity Distributions in Ultrarelativistic Heavy-Ion Collisions

  王宏民, 侯召宇, 孙献静

  理论物理通讯. 2012, 57(06): 1043-1047.

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  In this paper, the gluon distribution is extracted from the KLR-AdS/CFT saturation model and used to investigate net-baryon and net-kaon rapidity distributions in ultrarelativistic heavy-ion collisions. With the same parameters of the saturation model fitting to HERA data and an χ² analysis of the overall constant C, the theoretical results are in good agreement with RHIC data in Au+Au collisions at √s=0.2 TeV. Then, we present the predictive results for net-baryon rapidity distributions in central Pb+Pb collisions at LHC energies of √s=2.76, 3.94, and 5.52 TeV, and give the corresponding values of d N/d y for net-baryon at y=0.
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  Theoretical Study on the Low-Lying Electronic States of He₂, He₂⁺, and He₂⁺⁺

  张云光, 查新未, 高涛

  理论物理通讯. 2012, 57(06): 1048-1052.

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  The equilibrium geometries, potential energy curves, spectroscopic dissociation energies of the ground and low-lying electronic states of He₂, He₂⁺ and He₂⁺⁺ are calculated using symmetry adapted cluster/symmetry adapted cluster-configuration interaction (SAC/SAC-CI) method with the basis sets CC-PV5Z. The corresponding dissociation limits for all states are derived based on atomic and molecular reaction statics. The analytical potential energy functions of these states are fitted with Murrell--Sorbie potential energy function from our calculation results. The spectroscopic constants B_e, α _e, ω _e, and ω _e χ _e of these states are calculated through the relationship between spectroscopic data and analytical energy function, which are in well agreement with the experimental data. In addition, the origin of the energy barrier in the ground state X¹Σ_g⁺ of He₂⁺⁺ energy curve are explained using the avoided crossing rules of valence bond model.
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  Manipulating Photoelectron Distributions for Rare Gas Atoms Ionized with Polarized Femtosecond Laser Pulses

  李小刚

  理论物理通讯. 2012, 57(06): 1053-1058.

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  Above-threshold ionizations of rare gas atoms excited by polarized femtosecond laser pulses are investigated. The photoelectron momentum spectra are obtained applying the strong-field approximation (SFA) theory. It is found that, distribution of the emitted photoelectrons varies with different polarizations of laser pulses. We have interpreted the relationship between the observed distribution and the laser polarization taking advantage of tunneling ionization theory and simple-man model. The polarization sensitivity indicates that one can easily manipulate the photoelectron distribution by controlling the polarization of the exciting pulse.
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  Calculation of Excited States of He Atoms in a Strong Magnetic Field

  赵力波, B.C. Saha, 杜孟利

  理论物理通讯. 2012, 57(06): 1059-1065.

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  A recently developed B-spline algorithm is extended and utilized to calculate excited states of He atoms in the presence of strong magnetic fields. Binding energies are presented for He in the five excited atomic states 2¹0⁺, 1¹0^-, 2¹0^-, 1¹(-1)⁺, and 2¹(-1)⁺ with magnetic field strength ranging from 0.0001 to 10 a.u. The obtained energies are compared with available theoretical data, and found to be in good agreement. We investigate influence of magnetic fields on atomic structures of multielectron atoms, and illustrate that how electron probability density distributions change with increasing magnetic field strength. The current approach is directly applicable to simulations of discrete spectra for He atoms in the atmospheres of magnetized white dwarf stars.
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  Multiple Image Method for the Two Conductor Spheres in a Uniform Electrostatic Field

  高欣, 胡林, 孙刚

  理论物理通讯. 2012, 57(06): 1066-1070.

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  A method using multiple mirror images of point charges is put forward to analyze the polarization of two identical conductor spheres in a uniform electrostatic field. By use of the method, the electric field distribution and the interaction force between two spheres can be calculated accurately even for very small gap between two spheres. Our results show that the magnitude of the product of the gap between two spheres and the local electric field in the center of the gap is approximately in the same order and the interaction between two spheres increases very fast as the two spheres are close to each other. We also show that the interaction force between two conductor spheres is almost same with that between two dielectric spheres with high permittivity.
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  Spin Splitting in Different Semiconductor Quantum Wells

  郝亚非

  理论物理通讯. 2012, 57(06): 1071-1075.

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  We theoretically investigate the spin splitting in four undoped asymmetric quantum wells in the absence of external electric field and magnetic field. The quantum well geometry dependence of spin splitting is studied with the Rashba and the Dresselhaus spin-orbit coupling included. The results show that the structure of quantum well plays an important role in spin splitting. The Rashba and the Dresselhaus spin splitting in four asymmetric quantum wells are quite different. The origin of the distinction is discussed in this work.
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  Quantum Wire with Triangle Cross Section: Optical Properties

  R. Khordad, S. Tafaroji, R. Katebi, A. Ghanbari

  理论物理通讯. 2012, 57(06): 1076-1080.

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  In the present work, the optical properties of a GaAs quantum wire with equilateral triangle cross section are studied. For this purpose, we use analytical expressions for optical properties obtained by the compact-density matrix formalism. Here, we investigate the intersubband optical absorption coefficients and refractive index changes as a function of the triangle side (L) and the incident optical intensity (I). According to the obtained results, it is found that: (i) The total refractive index changes increase and shift towards lower energies when the triangle side increases. (ii) The total absorption coefficient decreases as the triangle side increases. Also, the resonance peak shifts towards lower energies by increasing the triangle side.
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  Controllable Spin-Polarized Transport in a Three-Terminal Model

  梁峰, 杨永宏, 汪军

  理论物理通讯. 2012, 57(06): 1081-1086.

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  By means of the Keldysh Green's function method, we investigate the spin-polarized electron transport in a three-terminal device, which is composed of three normal metal leads and two serially-coupled quantum dots (QDs). The Rashba spin-orbit interaction (RSOI) is also considered in one of the QDs. We show that the spin-polarized charge current with arbitrary spin polarization can be obtained because of the quantum spin interference effect arising from the Rashba spin precession phase, and it can be modulated by the system parameters such as the applied external voltages, the RSOI strength, the QD levels, as well as the dot-lead coupling strengths. Moreover, a fully spin-polarized current or a pure spin current without any accompanying charge current can also be controlled to flow in the system. Our findings indicate that the proposed model can serve as an all-electrical spin device in spintronics field.
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  Negative Differential Resistance in Atomic Carbon Chain-Graphene Junctions

  安丽萍, 刘春梅, 刘念华

  理论物理通讯. 2012, 57(06): 1087-1090.

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  We investigate the electronic transport properties of atomic carbon chain-graphene junctions by using the density-functional theory combining with the non-equilibrium Green's functions. The results show that the transport properties are sensitively dependent on the contact geometry of carbon chain. From the calculated I-V curve we find negative differential resistance (NDR) in the two types of junctions. The NDR can be considered as a result of molecular orbitals moving related to the bias window.
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  Scaling Theory of Strongly Charged Cylindrical Polyelectrolyte Brushes

  瞿立建

  理论物理通讯. 2012, 57(06): 1091-1094.

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  Scaling theory of charged cylindrical polyelectrolyte brushes is developed. The dependence of brush thickness on the grafting density, charge fraction, and chain length is analyzed. A full phase diagram is established. Characteristics and boundaries between different regimes of cylindrical polyelectrolyte brushes are summarized. Special attentions are paid to electrostatic interaction induced stiffening and counterion condensation effects. If the Bjerrum length of the solution is larger than the Kuhn length of the polyelectrolyte chains, counterion condensation occurs in the strongly charged polyelectrolyte brushes. On the contrary, the electrostatic interaction stretches the strongly charged grafted polyelectrolyte chains to their contour length.
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  Phase Transitions in q-States Signal Reconstruction

  孙怡帆

  理论物理通讯. 2012, 57(06): 1095-1100.

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  Compressed sensing is a new signal acquisition method that acquires signal in a compressed form and then recovers the signal by the use of computational tools and techniques. This means fewer measurements of signal are needed and thus it will save huge amount of time and storage space. We, in this paper, consider the compressed sensing of sparse integer-valued signal (referred as “q-states signal” throughout the paper). In order to accelerate the speed of reconstruction, we adopt the sparse rather than dense measurement matrices. Using methods and tools developed in statistical physics, we locate the reconstruction limit for L₀-reconstruction method and propose a belief propagation-based algorithm that can deal with instance with large size and its typical reconstruction performance are also analyzed.
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  Quasinormal Modes of a Black Hole with Quintessence-Like Matter and a Deficit Solid Angle for Electromagnetic Perturbation

  王春艳, 赵亚峰, 高亚军

  理论物理通讯. 2012, 57(06): 1101-1104.

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  We investigate the electromagnetic perturbation around a black hole with quintessence-like matter and a deficit solid angle. The complex frequencies of the quasinormal modes of electromagnetic perturbation are evaluated by the third-order WKB approximation. The results show that the electromagnetic perturbation around the black hole damps more slowly owing to the presence of the quintessence-like. The phenomenon can be distinguished from the black hole only with a deficit angle.