理论物理通讯

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Integrable KP Coupling and Its Exact Solution

彭凌, 杨旭东, 楼森岳

理论物理通讯. 2012, 58(01): 1-4.

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The integrable coupling is one of the most important topics in the nonlinear physics. This paper creates a novel integrable KP coupling and solves it via a recently-developed dark parameterization procedure.

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Travelling Waves for a Density Dependent Diffusion Nagumo Equation over the Real Line

Robert A. Van Gorder

理论物理通讯. 2012, 58(01): 5-11.

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We consider the density dependent diffusion Nagumo equation, where the diffusion coefficient is a simple power function. This equation is used in modelling electrical pulse propagation in nerve axons and in population genetics (amongst other areas). In the present paper, the δ-expansion method is applied to a travelling wave reduction of the problem, so that we may obtain globally valid perturbation solutions (in the sense that the perturbation solutions are valid over the entire infinite domain, not just locally; hence the results are a generalization of the local solutions considered recently in the literature). The resulting boundary value problem is solved on the real line subject to conditions at z → ±∞. Whenever a perturbative method is applied, it is important to discuss the accuracy and convergence properties of the resulting perturbation expansions. We compare our results with those of two different numerical methods (designed for initial and boundary value problems, respectively) and deduce that the perturbation expansions agree with the numerical results after a reasonable number of iterations. Finally, we are able to discuss the influence of the wave speed c and the asymptotic concentration value α on the obtained solutions. Upon recasting the density dependent diffusion Nagumo equation as a two-dimensional dynamical system, we are also able to discuss the influence of the nonlinear density dependence (which is governed by a power-law parameter m) on oscillations of the travelling wave solutions.

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Path Integral Solution for an Angle-Dependent Anharmonic Oscillator

S. Haouat

理论物理通讯. 2012, 58(01): 12-18.

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We have given a straightforward method to solve the problem of noncentral anharmonic oscillator in three dimensions. The relative propagator is presented by means of path integrals in spherical coordinates. By making an adequate change of time we are able to separate the angular motion from the radial one. The relative propagator is then exactly calculated. The energy spectrum and the corresponding wave functions are obtained.

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Time-Dependent Action in φ⁶ Potential

Hatem Widyan, Mashhoor Al-Wardat

理论物理通讯. 2012, 58(01): 19-26.

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The false vacuum decay in field theory from a coherently oscillating initial state is studied for φ⁶ potential. An oscillating bubble solution is obtained. The instantaneous bubble nucleation rate is calculated.

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Exact Solutions of the Morse-like Potential, Step-Up and Step-Down Operators via Laplace Transform Approach

Altug Arda, Ramazan Sever

理论物理通讯. 2012, 58(01): 27-30.

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We intend to realize the step-up and step-down operators of the potential V (x) = V₁ e ^2βx + V₂ e ^βx. It is found that these operators satisfy the commutation relations for the SU(2) group. We find the eigenfunctions and the eigenvalues of the potential by using the Laplace transform approach to study the Lie algebra satisfied the ladder operators of the potential under consideration. Our results are similar to the ones obtained for the Morse potential (β → -β).

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Transformation Between Eigenfunctions of Three Components of Geometric Momentum on Two-Dimensional Sphere

孙浩然, 寻大毛, 唐良辉, 刘全慧

理论物理通讯. 2012, 58(01): 31-33.

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A technique of coordinate transformation is devised to overcome the computational difficulty associated with the direct transformation between eigenfunctions of three components of the geometric momentum on two-dimensional spherical surface, and the computations are firstly carried out in new coordinates and secondly the results are transformed back into the original coordinates. The eigenfunctions of different components of geometric momentum is explicitly demonstrated to transform under the spatial rotations in the precise way we anticipate.

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Self-trapping and Macroscopic Tunnelling of Superfluid Fermi Gases in Multi-well Potentials

徐红萍, 薛具奎

理论物理通讯. 2012, 58(01): 34-38.

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We study the tunnelling dynamics of superfluid Fermi gases trapped in multi-well system along the BEC-BCS crossover. Within the hydrodynamical model and by using the multi-mode approximation, the self-trapping dynamics of superfluid Fermi gases in multi-well system are obtained numerically. We find that the self-trapping to diffusion transition strongly depends on the well number. When the well number is less than three, the self-trapped state takes place easier on the BEC side than that on the BCS side. However, when the well number is larger than three, the self-trapped state takes place easier on the BCS side instead of the BEC side. Furthermore, by considering a superfluid of ⁴⁰K atoms, we obtain the zero-mode and π-mode Josephson frequencies of coherent atomic oscillations in double-well system. It is noteworthy that the Josephson mode, especially, the existence of π-mode frequency strongly depends on the atoms number on the BCS side.

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Quantum Correlation in Three-Qubit Heisenberg Model with Dzyaloshinskii-Moriya Interaction

田立君, 颜益营, 秦立国

理论物理通讯. 2012, 58(01): 39-46.

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We investigate the pairwise thermal quantum discord in a three-qubit XXZ model with Dzyaloshinskii-Moriya (DM) interaction. We find that the effects of DM interaction on antiferromagnetic system is distinct from that of ferromagnetic system. The magnetic field supplemented with DM term contribute to enhance the range of quantum discord. It is revealed that the situations where quantum discord fails to indicate a sudden change of groundstate at finite temperature though indicating such a sudden change of groundstate at zero temperature. Dynamics of pairwise thermal quantum discord is considered as well. Thermal quantum discord vanishes in asymptotic limit regardless of its initial values, however, thermal entanglement suddenly disappears in finite time.

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Probing Bell Diagonal State without Disturbing Its Correlations

李珍妮, 金家森, 于长水

理论物理通讯. 2012, 58(01): 47-50.

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In this paper, we propose a very simple scheme to probe the quantum and classical correlation including quantum entanglement of Bell diagonal state. In the probing process, the correlation of Bell diagonal state, even the state itself, is not disturbed, which means a non-destructive probing. In addition, our scheme can be performed even though the two qubits of the Bell diagonal state are separate in space.

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Attack on the Enhanced Multiparty Quantum Secret Sharing

杨帅, 陈秀波, 杨义先

理论物理通讯. 2012, 58(01): 51-54.

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Recently, Gao et al.'s [Commun. Theor. Phys. 52 (2009) 421] multiparty quantum secret sharing (MQSS) protocol with two-photon three-dimensional Bell states was enhanced by Hwang et al. [Commun. Theor. Phys. 56 (2011) 79]. The improved protocol removes some unnecessary unitary operations, devices, and transmissions by the technique of decoy single photons and careful modification. However, in this paper, we investigate the security of the improved protocol and find it is insecure. The eavesdropper can steal all Alice's secret information. Furthermore, a feasible modification to remedy the security loophole is put forward. Our improved protocol provides a basic method to modify a kind of MQSS protocols which cannot resist the collusion attack.

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A Model of Irregular Impurity at the Surface of Nanoparticle and Catalytic Activity

I.V. Blinova, V.V. Gusarov, I. Yu. Popov

理论物理通讯. 2012, 58(01): 55-58.

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A problem of nanocatalyst improvement is considered. The existence of irregularities at the surface of nanoparticle leads to the increasing of the surface/volume ratio and, correspondingly, to the improvement of the catalytic activity. But this impurity gives one an additional effect due to the change of the electronic density at the surface. We suggest simple model for the description of this effect. The model allows one to find the discrete spectrum of the Schrödinger operator for nanoparticle. Due to this impurity induced bound states the electron density increases near the surface. It leads to the increase of the catalytic activity of nanoparticles with surface impurities.

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Accelerating Vacua in Gauss-Bonnet Gravity

徐伟, 孟坤, 赵柳

理论物理通讯. 2012, 58(01): 59-62.

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Accelerating vacua with maximally symmetric, but not necessarily spherical, sections for Einstein and Gauss-Bonnet gravities in generic dimensions are obtained. The acceleration parameter has the effect of shifting the cosmological constants in Einstein gravity, whereas in Gauss-Bonnet gravity the effective cosmological constants remain the same in the presence of acceleration as in the case without acceleration.

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Dynamical Horizon Entropy Bound Conjecture in Loop Quantum Cosmology

李丽仿, 朱建阳

理论物理通讯. 2012, 58(01): 63-66.

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The covariant entropy bound conjecture is an important hint for the quantum gravity, with several versions available in the literature. For cosmology, Ashtekar and Wilson-Ewing ever show the consistence between the loop gravity theory and one version of this conjecture. Recently, He and Zhang [J. High Energy Phys. 10 (2007) 077] proposed a version for the dynamical horizon of the universe, which validates the entropy bound conjecture for the cosmology filled with perfect fluid in the classical scenario when the universe is far away from the big bang singularity. However, their conjecture breaks down near big bang region. We examine this conjecture in the context of the loop quantum cosmology. With the example of photon gas, this conjecture is protected by the quantum geometry effects as expected.

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Spatiotemporal Self-Similar Solutions of the Generalized (3+1)-dimensional Nonlinear Schrödinger Equation with Polynomial Nonlinearity of Arbitrary Order

朱海平

理论物理通讯. 2012, 58(01): 67-72.

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We construct analytical self-similar solutions for the generalized (3+1)-dimensional nonlinear Schrödinger equation with polynomial nonlinearity of arbitrary order. As an example, we list self-similar solutions of quintic nonlinear Schrödinger equation with distributed dispersion and distributed linear gain, including bright similariton solution, fractional and combined Jacobian elliptic function solutions. Moreover, we discuss self-similar evolutional dynamic behaviors of these solutions in the dispersion decreasing fiber and the periodic distributed amplification system.

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Bell Polynomial Approach and N-Soliton Solutions for a Coupled KdV-mKdV System

覃翌, 高以天, 于鑫, 蒙高庆

理论物理通讯. 2012, 58(01): 73-78.

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In fluid dynamics, plasma physics and nonlinear optics, Korteweg-de Vries (KdV)-type equations are used to describe certain phenomena. In this paper, a coupled KdV-modified KdV system is investigated. Based on the Bell polynomials and symbolic computation, the bilinear form of such system is derived, and its analytic N-soliton solutions are constructed through the Hirota method. Two types of multi-soliton interactions are found, one with the reverse of solitonic shapes, and the other, without. Both the two types can be considered elastic. For a pair of solutions to such system, u and v, with the number of solitons N even, the soliton shapes of u stay unvaried while those of v reverse after the interaction; with N odd, the soliton shapes of both u and v keep unchanged after the interaction.

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Collective Perspective on Advances in Dyson-Schwinger Equation QCD

理论物理通讯. 2012, 58(01): 79-134.

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We survey contemporary studies of hadrons and strongly interacting quarks using QCD's Dyson-Schwinger equations, addressing the following aspects: confinement and dynamical chiral symmetry breaking; the hadron spectrum; hadron elastic and transition form factors, from small- to large-Q²; parton distribution functions; the physics of hadrons containing one or more heavy quarks; and properties of the quark gluon plasma.

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An Investigation of ⁴He+¹²C and ⁴He+¹⁶O Reactions Using the Cluster Model

A.H. Al-Ghamdi, Awad A. Ibraheem, M. El-Azab Farid

理论物理通讯. 2012, 58(01): 135-140.

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The α -target semimicroscopic single folding potentials have been derived by folding a composite (repulsive and attractive) effective α-α interaction with the α -cluster distribution density in the target nuclei. The obtained potentials are considered as the real part of the nuclear optical model potentials, while the imaginary parts are phenomenologicaly expressed using the Woods-Saxon form. Nine sets of measured experimental data of the ⁴He+¹²C and ⁴He+¹⁶O elastic rainbow scattering over the energy range 80-240 MeV are analyzed using the obtained potentials. The data are successfully reproduced using the extracted potentials. The resulted reaction cross sections are also investigated and compared with the available corresponding data.

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A Simple Approach to Study the Isospin Effect in Mass Splitting of Three-Nucleon Systems by Using Hyperspherical Functions

H. Feizi, A.A. Rajabi, M.R. Shojaei

理论物理通讯. 2012, 58(01): 141-145.

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In this work, the binding energy and wavefunctions of three-nucleon systems are obtained by using hyperspherical harmonic approach. We have used a mathematical modification method to obtain the eigenvalues and eigenfunctions of Schrödinger equation for three-nucleon systems in calculation. Next, we have used a simple approach to obtain the difference between binding energy of ³H and ³He where gives us mass splitting of three-nucleon systems. We have compared our results with the other works and experimental values.

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Alpha Decay Half-Lives of Some Nuclei from Ground State to Ground State with Yukawa Proximity Potential

E. Javadimanesh, H. Hassanabadi, A.A. Rajabi, H. Rahimov, S. Zarrinkamar

理论物理通讯. 2012, 58(01): 146-150.

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We study the half-lives of some nuclei via the alpha-decay process from ground state to ground state. To go through the problem, we have considered a potential model with Yukawa proximity potential and have thereby calculated the half-lives. The comparison with the existing data is motivating.

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Slow Light in One-Dimensional Coupled-Resonator Waveguide Controlling by an Electric Field

程木田

理论物理通讯. 2012, 58(01): 151-154.

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The photon transport properties in one-dimensional coupled-resonator waveguide embedded with a quantum dot molecule are investigated. The calculations reveal that one can control the photon transport by using a gate electric field. The phase shift and group velocity delay of the transmitted single photon are discussed. This research may be found applications in integrated optoelectronic devices and solid quantum devices.

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Bose-Einstein Condensation of Photons and Photon Pairs

张建军, 袁建辉, 张俊佩, 成泽

理论物理通讯. 2012, 58(01): 155-159.

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We investigate the Bose-Einstein condensation of photons and photon pairs in a two-dimension optical microcavity. We find that in the paraxial approximation, the mixed gas of photons and photon pairs is formally equivalent to a two dimension system of massive bosons with non-vanishing chemical potential, which implies the existence of two possible condensate phase. We also discuss the quantum phase transition of the system and obtain the critical point analytically. Moreover, we find that the quantum phase transition of the system can be interpreted as second harmonic generation.

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Equation of State for Shock Compressed Xenon in the Ionization Regime: ab Initio Study

王聪, 顾云军, 陈其峰, 贺贤土, 张平

理论物理通讯. 2012, 58(01): 160-164.

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Quantum molecular dynamic (QMD) simulations have been applied to study the thermophysical properties of liquid xenon under dynamic compressions. The equation of state (EOS) obtained from QMD calculations are corrected according to Saha equation, and contributions from atomic ionization, which are of predominance in determining the EOS at high temperature and pressure, are considered. For the pressures below 160 GPa, the necessity in accounting for the atomic ionization has been demonstrated by the Hugoniot curve, which shows excellent agreement with previous experimental measurements, and three levels of ionization have been proved to be sufficient at this stage.

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A Unified Spatio-Temporal Framework of the Cuerno-Barabasi Stochastic Continuum Model of Surface Sputtering

Oluwole Emmanuel Oyewande

理论物理通讯. 2012, 58(01): 165-170.

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The nonlinear continuum model proposed by Cuerno and Barabasi is the most successful and widely acceptable theoretical description of oblique incidence ion sputtered surfaces to date and is quite robust in its predictions of the time evolution and scaling of interfaces driven by ion bombardment. However, this theory has thus far predicted only ripple topographies and rough surfaces for short and large scales, respectively. As a result, its application to the interpretation and study of nanodots, predicted by Monte Carlo simulations for, and observed in experiments of, oblique incidence sputtering is still unclear and, hence, an open problem. In this paper, we provide a new insight to the theory, within the same length scale, that explains nanodot formation on off-normal incidence sputtered surfaces, among others, and propose ways of observing the predicted topographies of the MC simulations, as well as possible control of the size of the nanodots, in the framework of the Cuerno-Barabasi continuum theory.

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Effects of Unintended Dopants on I-V Characteristics of the Double-Gate MOSFETs, a Simulation Study

李佩成, 梅光辉, 胡光喜, 王伶俐, 刘冉, 汤庭鳌

理论物理通讯. 2012, 58(01): 171-174.

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In this paper, we study the effects of an unintended dopant in the channel on the current-voltage characteristics of a Double-Gate (DG) Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET). Non-Equilibrium Green's Function (NEGF) approach is used. A quantum transport model to calculate the drain current is presented and subthreshold swing and drain induced barrier lowering (DIBL) effect are studied.

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2012年, 第58卷, 第01期　
刊出日期：2012-07-15

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2012年, 第58卷, 第01期 刊出日期：2012-07-15

2012年, 第58卷, 第01期　
刊出日期：2012-07-15