2012年, 第58卷, 第02期　
刊出日期：2012-08-15

  

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  Approximate Derivative-Dependent Functional Variable Separation for the Generalized Diffusion Equations with Perturbation

  张顺利, 吉飞宇, 屈长征

  理论物理通讯. 2012, 58(02): 175-181.

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  As an extension to the derivative-dependent functional variable separation approach, the approximate derivative-dependent functional variable separation approach is proposed, and it is applied to study the generalized diffusion equations with perturbation. Complete classification of these perturbed equations which admit approximate derivative-dependent functional separable solutions is obtained. As a result, the corresponding approximate derivative-dependent functional separable solutions to some resulting perturbed equations are derived by way of examples.
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  Approximate Solutions of Nonlinear Fractional Kolmogorov-Petrovskii-Piskunov Equations Using an Enhanced Algorithm of the Generalized Two-Dimensional Differential Transform Method

  宋丽娜, 王维国

  理论物理通讯. 2012, 58(02): 182-188.

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  By constructing the iterative formula with a so-called convergence-control parameter, the generalized two-dimensional differential transform method is improved. With the enhanced technique, the nonlinear fractional Kolmogorov-Petrovskii-Piskunov equations are dealt analytically and approximate solutions are derived. The results show that the employed approach is a promising tool for solving many nonlinear fractional partial differential equations. The algorithm described in this work is expected to be employed to solve more problems in fractional calculus.
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  Homogenization for Periodic Heterogeneous Materials with Arbitrary Position-Dependent Material Properties

  徐志杰

  理论物理通讯. 2012, 58(02): 189-194.

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  We present a rigorous homogenization approach for efficient computation of a class of physical problems in a one-dimensional periodic heterogeneous material. This material is represented by a spatially periodic array of unit cells with a length of ε. More specifically, the method is applied to the diffusion, heat conduction, and wave propagation problems. Heterogeneous materials can have arbitrary position-dependent continuous or discontinuous materials properties (for example heat conductivity) within the unit cell. The final effective model includes both effective properties at the leading order and high-order contributions due to the microscopic heterogeneity. A dimensionless heterogeneity parameter β is defined to represent high-order contributions, shown to be in the range of [-1/12, 0], and has a universal expression for all three problems. Both effective properties and heterogeneity parameter β are independent of ε, the microscopic scale of heterogeneity. The homogenized solution describing macroscopic variations can be obtained from the effective model. Solution with sub-unit-cell accuracy can be constructed based on the homogenized solution and its spatial derivatives. The paper represents a general approach to obtain the effective model for arbitrary periodic heterogeneous materials with position-dependent properties.
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  Relativistic Treatment of Spinless Particles Subject to a Tietz-Wei Oscillator

  孙国华, 董世海

  理论物理通讯. 2012, 58(02): 195-197.

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  The bound state solutions of the relativistic Klein-Gordon equation with the Tietz-Wei diatomic molecular potential are presented for the s wave. It is shown that the solutions can be expressed by the generalized hypergeometric functions. The normalized wavefunctions are also derived.
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  Thermal Spin Squeezing as a Signature of Thermal Global Entanglement in Heisenberg Models

  Mojtaba Jafarpour, Azita Naji

  理论物理通讯. 2012, 58(02): 198-204.

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  We study thermal spin squeezing (TSS) and thermal global entanglement (TGE) in a general Heisenberg spin chain, in the presence of Dzyaloshinskii-Moriya interaction and an external magnetic field. We derive an inequality associating the squeezing parameter and the global concurrence, which establishes (TSS) as a signature of (TGE). The inequality reduces to equality for particular symmetric chains which also associates TSS with bipartite entanglement in such systems. We also check the results by presenting two numerical examples.
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  Klein Paradox of Two-Dimensional Dirac Electrons in Circular Well Potential

  黄海, 付星球, 韩榕生

  理论物理通讯. 2012, 58(02): 205-208.

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  We study two-dimensional massive Dirac equation in circular well potential. The energies of bound states are obtained. We demonstrate the Klein paradox of this relativistic wave equation: For large enough potential depth, the bound states disappear from the spectra. Applications to graphene systems are discussed.
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  Minimax Strategy of Optimal Unambiguous State Discrimination

  张文海, 余龙宝, 曹卓良, 叶柳

  理论物理通讯. 2012, 58(02): 209-212.

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  In this paper, we consider the minimax strategy to unambiguously discriminate two pure nonorthogonal quantum states without knowing a priori probability. By exploiting the positive-operator valued measure, we derive the upper bound of the minimax measurement of the optimal unambiguous state discrimination. Based on the linear optical devices, we propose an experimentally feasible scheme to implement a minimax measure of a general pair of two nonorthogonal quantum states.
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  Effects of Quantum Noise on Quantum Clock Synchronization

  谢端, 彭进业

  理论物理通讯. 2012, 58(02): 213-219.

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  In laboratory environment, the channel apparatus will generate particular dominant quantum noise. The noise then will give rise to some errors during synchronization. In this work, the accuracies of one qubit transport protocol and entangled states transport protocol in the presence of noise have been studied. With the help of three important and familiar noise models, the quantum noise will degrade the accuracy has been proved. Due to the influence of quantum noise, the accuracy of entangled qubits decrease faster than that of one qubit. The entangled states will improve the accuracy in noise-free channel, and will degrade the accuracy in noise channel.
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  Return Probability of the Fibonacci Quantum Walk

  CLEMENT AMPADU

  理论物理通讯. 2012, 58(02): 220-224.

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  In this paper the return probability of the one-dimensional discrete-time quantum walk is studied. We derive probabilistic formulas for the return probability related to the quantum walk governed by the Fibonacci coin.
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  Controlled Phase Flip Gate and Its Application in Low-Q Cavities by Single-Photon Input-Output Process

  王波, 陈琼, 杨万里, 寇谡鹏

  理论物理通讯. 2012, 58(02): 225-228.

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  By employing an auxiliary cavity, we investigate the possibility to implement the conditional phase flip (CPF) gate on two atoms confined in separate low-Q cavities by single-photon input-output process, based on the Faraday rotation. This indicates a universal quantum computing available with sophisticated cavity QED techniques. As examples, we carry out generation of cluster states of distant atomic qubits and accomplish a teleportation based on Bell-state measurement in low-Q cavities.
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  Casimir Effect at Finite Temperature in the Presence of One Fractal Extra Compactified Dimension

  程红波

  理论物理通讯. 2012, 58(02): 229-236.

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  We discuss the Casimir effect for massless scalar fields subject to the Dirichlet boundary conditions on the parallel plates at finite temperature in the presence of one fractal extra compactified dimension. We obtain the Casimir energy density with the help of the regularization of multiple zeta function with one arbitrary exponent and further the renormalized Casimir energy density involving the thermal corrections. It is found that when the temperature is sufficiently high, the sign of the Casimir energy remains negative no matter how great the scale dimension δ is within its allowed region. We derive and calculate the Casimir force between the parallel plates affected by the fractal additional compactified dimension and surrounding temperature. The stronger thermal influence leads the force to be stronger. The nature of the Casimir force keeps attractive.
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  de Sitter Tunneling, Emission Spectrum and Entropy/Area Quantum

  蒋青权

  理论物理通讯. 2012, 58(02): 237-243.

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  The Banerjee-Majhi's recent work shows that the Hawking radiation and entropy/area quantum of the black hole horizon (EH) can be well described in the tunneling picture. In this paper, we develop this idea to the case of a de Sitter tunneling from the cosmological horizon (CH), and obtain the Hawking emission spectrum and entropy/area spectroscopy from the CH of the purely de Sitter black hole as well as the Schwarzschild-de Sitter black hole. It is interestingly found that the area of the CH is quantized by Δ A=4l_pl², as was given by Hod for the area quantum of -the EH by considering the Heisenberg uncertainty principle and Schwinger-type emission process. Also, we conclude from our derivation that the entropy/area quantum of the CH is universal in the sense that it is independent of the black hole parameters. This realization implies that, (at least) at a semiclassical level, the de Sitter gravity shares the similar quantum behavior as the usual gravity without presence of a cosmological constant.
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  Multi-Soliton Solutions and Integrable Discretization for a Coupled Modified Volterra Lattice Equation

  赵海琼, 朱佐农

  理论物理通讯. 2012, 58(02): 244-250.

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  In this paper, we study a coupled modified Volterra lattice equation which is an integrable semidiscrete version of the coupled KdV and the coupled mKdV equation. By using the Darboux transformation, we obtain its new explicit solutions including multi-soliton and multi-positon. Furthermore, an integrable discretization of the coupled modified Volterra lattice equation is constructed.
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  Decay Process of Quantum Open System at Finite Temperatures

  肖骁, 高一波

  理论物理通讯. 2012, 58(02): 251-254.

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  Starting from the formal solution to the Heisenberg equation, we revisit an universal model for a quantum open system with a harmonic oscillator linearly coupled to a boson bath. The analysis of the decay process for a Fock state and a coherent state demonstrate that this method is very useful in dealing with the problems in decay process of the open system. For finite temperatures, the calculations of the reduced density matrix and the mean excitation number for the open system show that an initial coherent state will evolve into a temperature-dependant coherent state after tracing over the bath variables. Also in short-time limit, a temperature-dependant effective Hamiltonian for the open system characterizes the decay process of the open system.
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  Spatiotemporal Rogue Waves for the Variable-Coefficient (3+1)-Dimensional Nonlinear Schrödinger Equation

  王悦悦, 戴朝卿

  理论物理通讯. 2012, 58(02): 255-260.

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  With the help of the similarity transformation connected the variable-coefficient (3+1)-dimensional nonlinear Schrödinger equation with the standard nonlinear Schrödinger equation, we firstly obtain first-order and second-order rogue wave solutions. Then, we investigate the controllable behaviors of these rogue waves in the hyperbolic dispersion decreasing profile. Our results indicate that the integral relation between the accumulated time T and the real time t is the basis to realize the control and manipulation of propagation behaviors of rogue waves, such as sustainment and restraint. We can modulate the value T₀ to achieve the sustained and restrained spatiotemporal rogue waves. Moreover, the controllability for position of sustainment and restraint for spatiotemporal rogue waves can also be realized by setting different values of X₀.
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  Revisiting the Twist-3 Distribution Amplitudes of K Meson Within the QCD Background Field Approach

  钟涛, 吴兴刚, 韩华勇, 廖其力, 付海斌, 方祯云

  理论物理通讯. 2012, 58(02): 261-270.

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  In the present paper, we investigate the kaon twist-3 distribution amplitudes (DAs) φ_p,σ^K within the QCD background field approach. The SU_f(3)-breaking effects are studied in detail under a systematical way, especially the sum rules for the moments of φ_p,σ^K are obtained by keeping all the mass terms in the s-quark propagator consistently. After adding all the uncertainties in quadrature, the first two Gegenbauler moments of φ_p,σ^K are a_K,p¹ (1 GeV) = -0.376_-0.148^+0.103, a_K,p²(1 GeV) = 0.701_-0.491^+0.481, a_K,σ¹ (1 GeV) = -0.160_-0.074^+0.051, and a_K,σ²(1 GeV) = 0.369_-0.149^+0.163, respectively. Their normalization parameters μ_K^p|1 m GeV = 1.188_-0.043^+0.039 GeV and μ_K^σ|1 m GeV = 1.021_-0.055^+0.036 GeV. A detailed discussion on the properties of φ_p,σ^K moments shows that the higher-order s-quark mass terms can indeed provide sizable contributions. Furthermore, based on the newly obtained moments, a model for the kaon twist-3 wavefunction Ψ_p,σ^K(x,k⊥) with a better end-point behavior is constructed, which shall be useful for perturbative QCD calculations. As a byproduct, we make a discussion on the properties of the pion twist-3 DAs.
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  Adiabatic and Non-Adiabatic Berry Phases in Generalized J-C Model of Multi-Photon Process

  刘妮, 王月明, 梁九卿

  理论物理通讯. 2012, 58(02): 271-274.

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  We derive the adiabatic and non-adiabatic Berry phases in the generalized Jaynes-Cummings model of multi-photon process. The results show that the adiabatic Berry phase is kept a constant π independent of all the parameters, while the non-adiabatic approximate Berry phase is parameter-dependent, proportional to the average photon number m, and tends to be constant with the increasing detuning. In the case of exact n-photon resonance and an integer ratio of m/n, the two results coincide with each other, otherwise there appears an additional non-trivial phase factor.
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  A Theoretical Study of a Single-Walled ZnO Nanotube as a Sensor for H₂O Molecules

  段满益, 石国升, 王春雷, 周丽萍, 陈向荣, 方海平

  理论物理通讯. 2012, 58(02): 275-279.

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  We have studied the property of single-walled ZnO nanotubes with adsorbed water molecules, and theoretically designed a new sensor for detecting water molecules using single-walled ZnO nanotubes using a combination of density functional theory and the non-equilibrium Green's function method. Details of the geometric structures and adsorption energies of the H₂O molecules on the ZnO nanotube surface have been investigated. Our computational results demonstrate that the formation of hydrogen bonding between the H₂O molecules and the ZnO nanotube, and adsorption energies of the H₂O molecules on the ZnO nanotube are larger than the adsorption energies of other gas molecules present in the atmospheric environment. Moreover, the current-voltage curves of the ZnO nanotube with and without H₂O molecules adsorbed on its surface are calculated, the results of which showed that the H₂O molecules form stable adsorption configurations that could lead to the decrease in current. These results suggest that the single-walled ZnO nanotubes are able to detect and monitor the presence of H₂O molecules by applying bias voltages.
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  Zero Energy Anomaly in One-Dimensional Anderson Lattice with Exponentially Correlated Weak Diagonal Disorder

  王宗国, 覃绍京, 康凯, 王垂林

  理论物理通讯. 2012, 58(02): 280-284.

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  We calculated numerically the localization length of one-dimensional Anderson model with correlated diagonal disorder. For zero energy point in the weak disorder limit, we showed that the localization length changes continuously as the correlation of the disorder increases. We found that higher order terms of the correlation must be included into the current perturbation result in order to give the correct localization length, and to connect smoothly the anomaly at zero correlation with the perturbation result for large correlation.
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  Matrix Product State, Quantum Entanglement, and Criticality in the One-Dimensional Dimerized Antiferromagnetic Heisenberg Model

  刘光华, 田光善

  理论物理通讯. 2012, 58(02): 285-291.

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  The matrix product state (MPS) is utilized to investigate the ground state properties and quantum phase transitions (QPTs) of the dimerized antiferromagnetic Heisenberg (DAH) model. The ground state MPS wavefunctions determined by the infinite time-evolving block decimation (iTEBD) algorithm are shown to be very efficient descriptions of DAH model. In the thermodynamic limit, the quantum entanglement, the bond energy, and the nearest-neighbor correlations are calculated. It is revealed that the singular behavior of the bipartite entanglement can detect the QPTs directly. The critical point J₂^c =1.0 is determined evidently, and the quantum phase transition is argued to belong to the second-order category. At the critical point, logarithmic divergent character of the block entanglement is observed, and the system can be described by a free bosonic field theory.
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  Density-Density Propagator of the Luttinger Model of Spin-Half Fermions after an Interaction Quench

  周宗立, 袁兴红, 穆姝慧, 赵艳, 娄平, 章国顺

  理论物理通讯. 2012, 58(02): 292-294.

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  Motivated by recent research achievement of quantum interacting systems in non-equilibrium, we consider a Luttinger model with a suddenly switched-on interaction proposed by Cazalilla [M.A. Cazalilla, Phys. Rev. Lett. 97 (2006) 156403]. In order to compare with real systems, we extend Cazalilla's scenario to the spinful system. To find the influence of initial states on the time evolution of some non-equilibrium systems, we mainly focus on the density-density propagator. By comparison and analysis, we discover the different behavior of this non-equilibrium system. Further, it is found that the propagator saves strong memory of initial state, and the effects of right-left interaction cancel out in total density-density propagator.
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  Heat Generation by Electrical Current in Quantum Dot System with Fano Resonance

  陈桥, 许迈昌, 屈喜龙

  理论物理通讯. 2012, 58(02): 295-299.

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  We study the heat generation in quantum dot system with Fano resonance by nonequilibrium Green's functions method. The Fano resonance influences the heat generation significantly. As ξ increases, the heat generation decreases gradually. From the study of Q-eV curves, we find that the linewidth function Γ has huge influence on the heat generation. The Q-eV curves display obvious steps when the linewidth function Γ is small. However, these steps disappear with Γ increasing. As the source-drain bias eV increases, the Q-eV_g curves also display interesting behaviors.
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  A Macro Model for Traffic Flow with Consideration of Static Bottleneck

  唐铁桥, 李鹏, 吴永洪, 黄海军

  理论物理通讯. 2012, 58(02): 300-306.

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  In this paper, we develop a macro model for traffic flow with consideration of static bottleneck to explore the impacts of static bottleneck on traffic flow. The analytical and numerical results show that the proposed model can qualitatively describe the equilibrium flux, uniform flow and small perturbation under the action of a static bottleneck.
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  Influence of Control Parameters on the Competition Between Spiral Waves and Target Waves

  钱郁, 李伟, 黄晓东, 弭元元, 张朝阳

  理论物理通讯. 2012, 58(02): 307-312.

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  In this paper we systematically investigate the influence of control parameters on the competition results between spiral waves and target waves. Driving frequency f, amplitude A and injection area n of the input signals are three important parameters and the competition results between spiral waves and target waves are influenced by these three parameters remarkably. Based on these understandings we can control spiral waves effectively by suitable combination these parameters to generate faster target waves. And the effective controllable parameter regions are also studied.
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  Effect of Correlations on the Exponents for the Power-Law Distributions in Self-Organized Criticality

  邓永菊, 郑华, 杨纯斌

  理论物理通讯. 2012, 58(02): 313-316.

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  The origin of power-law distributions in self-organized criticality is investigated by treating the variation of the number of active sites in the system as a stochastic process. An avalanche is mapped to a first-return random-walk process in a one-dimensional lattice. In order to understand the reason of variant exponents for the power-law distributions in different self-organized critical systems, we introduce the correlations among evolution steps. Power-law distributions of the lifetime and spatial size are found when the random walk is unbiased with equal probability to move in opposite directions. It is found that the longer the correlation length, the smaller values of the exponents for the power-law distributions.