2018年, 第69卷, 第03期　
刊出日期：2018-03-01

  

• 全选
  |

• Select
  Dynamics of the Smooth Positons of the Wadati-Konno-Ichikawa Equation

  王改华, 张永帅, 贺劲松

  理论物理通讯. 2018, 69(03): 227-232.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  We discuss a modified Wadati-Konno-Ichikawa (mWKI) equation, which is equivalent to the WKI equation by a hodograph transformation. The explicit formula of degenerated solution of mWKI equation is provided by using degenerate Darboux transformation with respect to the eigenvalues, which yields two kinds of smooth solutions possessing the vanishing and nonvanishing boundary conditions respectively. In particular, a method for the decomposition of modulus square is operated to the positon solution, and the approximate orbits before and after collision of positon solutions are displayed explicitly.
• Select
  Gravitational Field as a Pressure Force from Logarithmic Lagrangians and Non-Standard Hamiltonians: The Case of Stellar Halo of Milky Way

  Rami Ahmad El-Nabulsi

  理论物理通讯. 2018, 69(03): 233-240.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  Recently, the notion of non-standard Lagrangians was discussed widely in literature in an attempt to explore the inverse variational problem of nonlinear differential equations. Different forms of non-standard Lagrangians were introduced in literature and have revealed nice mathematical and physical properties. One interesting form related to the inverse variational problem is the logarithmic Lagrangian, which has a number of motivating features related to the Liénard-type and Emden nonlinear differential equations. Such types of Lagrangians lead to nonlinear dynamics based on non-standard Hamiltonians. In this communication, we show that some new dynamical properties are obtained in stellar dynamics if standard Lagrangians are replaced by Logarithmic Lagrangians and their corresponding non-standard Hamiltonians. One interesting consequence concerns the emergence of an extra pressure term, which is related to the gravitational field suggesting that gravitation may act as a pressure in a strong gravitational field. The case of the stellar halo of the Milky Way is considered.
• Select
  Solution of Spin and Pseudo-Spin Symmetric Dirac Equation in (1+1) Space-Time Using Tridiagonal Representation Approach

  I. A. Assi, A. D. Alhaidari, H. Bahlouli

  理论物理通讯. 2018, 69(03): 241-256.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  The aim of this work is to find exact solutions of the Dirac equation in (1+1) space-time beyond the already known class. We consider exact spin (and pseudo-spin) symmetric Dirac equations where the scalar potential is equal to plus (and minus) the vector potential. We also include pseudo-scalar potentials in the interaction. The spinor wavefunction is written as a bounded sum in a complete set of square integrable basis, which is chosen such that the matrix representation of the Dirac wave operator is tridiagonal and symmetric. This makes the matrix wave equation a symmetric three-term recursion relation for the expansion coefficients of the wavefunction. We solve the recursion relation exactly in terms of orthogonal polynomials and obtain the state functions and corresponding relativistic energy spectrum and phase shift.
• Select
  Tidal Forces in Dyonic Reissner-Nördstrom Black Hole

  M. Sharif, Lubna Kousar

  理论物理通讯. 2018, 69(03): 257-262.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  This paper investigates the tidal as well as magnetic charge effects produced in dyonic Reissner-Nordström black hole. We evaluate Newtonian radial acceleration using radial geodesics for freely falling test particles. We establish system of equations governing radial and angular tidal forces using geodesic deviation equation and discuss their solutions for bodies falling freely towards this black hole. The radial tidal force turns out to be compressing outside the event horizon whereas the angular tidal force changes sign between event and Cauchy horizons unlike Schwarzschild black hole. The radial geodesic component starts decreasing in dyonic Reissner-Nordström black hole unlike Schwarzschild case. We conclude that magnetic charge strongly affects the radial as well as angular components of tidal force.
• Select
  Triviality of Quantum Electrodynamics Revisited

  D. Djukanovic, J. Gegelia, Ulf-G. Meißner

  理论物理通讯. 2018, 69(03): 263-265.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  Quantum electrodynamics is often considered to be a trivial theory. This is based on a number of evidences, both numerical and analytical. One of the strong indications for triviality of QED is the existence of the Landau pole for the running coupling. We show that by treating QED as the leading order approximation of an effective field theory and including the next-to-leading order corrections, the Landau pole is removed. We also analyze the cutoff dependence of the bare coupling at two-loop order and conclude that the conjecture, that for reasons of self-consistency, QED needs to be trivial is a mere artefact of the leading order approximation to the corresponding effective field theory.
• Select
  Current Reversals of an Underdamped Brownian Particle in an Asymmetric Deformable Potential

  蔡纯纯, 刘建立, 陈浩, 李丰果

  理论物理通讯. 2018, 69(03): 266-270.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  Transport of an underdamped Brownian particle in a one-dimensional asymmetric deformable potential is investigated in the presence of both an ac force and a static force, respectively. From numerical simulations, we obtain the current average velocity. The current reversals and the absolute negative mobility are presented. The increasing of the deformation of the potential can cause the absolute negative mobility to be suppressed and even disappear. When the static force is small, the increase of the potential deformation suppresses the absolute negative mobility. When the force is large, the absolute negative mobility disappears. In particular, when the potential deformation is equal to 0.015, the two current reversals present with the increasing of the force. Remarkably, when the potential deformation is small, there are three current reversals with the increasing of the friction coefficient and the average velocity presents a oscillation behavior.
• Select
  Fixed-Time Outer Synchronization of Complex Networks with Noise Coupling

  侍红军, 苗连英, 孙永征, 刘茂省

  理论物理通讯. 2018, 69(03): 271-279.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  In this paper, the fixed-time outer synchronization of complex networks with noise coupling is investigated. Based on the theory of fixed-time stability and matrix inequalities, sufficient conditions for fixed-time outer synchronization are established and the estimation of the upper bound of the setting time is obtained. The result shows that the setting time can be adjusted to a desired value regardless of the initial states. Numerical simulations are performed to verify the effectiveness of the theoretical results. The effects of control parameters and the density of controlled nodes on the converging time are studied.
• Select
  Self-Organized Criticality in an Anisotropic Earthquake Model

  李斌全, 王圣军

  理论物理通讯. 2018, 69(03): 280-284.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  We have made an extensive numerical study of a modified model proposed by Olami, Feder, and Christensen to describe earthquake behavior. Two situations were considered in this paper. One situation is that the energy of the unstable site is redistributed to its nearest neighbors randomly not averagely and keeps itself to zero. The other situation is that the energy of the unstable site is redistributed to its nearest neighbors randomly and keeps some energy for itself instead of reset to zero. Different boundary conditions were considered as well. By analyzing the distribution of earthquake sizes, we found that self-organized criticality can be excited only in the conservative case or the approximate conservative case in the above situations. Some evidence indicated that the critical exponent of both above situations and the original OFC model tend to the same result in the conservative case. The only difference is that the avalanche size in the original model is bigger. This result may be closer to the real world, after all, every crust plate size is different.
• Select
  Perturbative Power Counting, Lowest-Index Operators and Their Renormalization in Standard Model Effective Field Theory

  廖益, 马小东

  理论物理通讯. 2018, 69(03): 285-290.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  We study two aspects of higher dimensional operators in standard model effective field theory. We first introduce a perturbative power counting rule for the entries in the anomalous dimension matrix of operators with equal mass dimension. The power counting is determined by the number of loops and the difference of the indices of the two operators involved, which in turn is defined by assuming that all terms in the standard model Lagrangian have an equal perturbative power. Then we show that the operators with the lowest index are unique at each mass dimension d, i.e., (H^† H)^d/2 for even d ≥ 4, and (L^T∈ H) C(L^T∈ H)^T(H^† H)^(d-5)/2 for odd d ≥ 5. Here H, L are the Higgs and lepton doublet, and ∈, C the antisymmetric matrix of rank two and the charge conjugation matrix, respectively. The renormalization group running of these operators can be studied separately from other operators of equal mass dimension at the leading order in power counting. We compute their anomalous dimensions at one loop for general d and find that they are enhanced quadratically in d due to combinatorics. We also make connections with classification of operators in terms of their holomorphic and anti-holomorphic weights.
• Select
  Hidden-charm Pentaquark Production at e⁺e^- Colliders

  李世渊, 刘言锐, 刘雨男, 司宗国, 张晓锋

  理论物理通讯. 2018, 69(03): 291-296.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  We study one possible production mechanism for the hidden-charm pentaquark via a color-octet cc pair fragmentation in e⁺e^- collision. The pentaquark production at B factory energy is dominated by e⁺e^-→ccg→ P_c+X, while at Z⁰ pole energy, there are several partonic processes playing significant role. Our results show that it is possible to search for the direct pentaquark production signal at e⁺e^- colliders, which is important to understand the properties of pentaquark.
• Select
  Higgs and Bottom Quarks Associated Production at High Energy Colliders in the Littlest Higgs Model with T-Parity

  侯镖锋, 张华莹, 毕恒恒

  理论物理通讯. 2018, 69(03): 297-302.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  In the littlest Higgs Model with T-parity, we discuss the Higgs production in association with bottom quarks at the LHC and future electron-positron collider. We calculate the cross sections of production channels pp→bbH, bb→H and bg→bH at 14 TeV LHC and the cross sections of production channel e⁺ e^-→ bbH in (un)polarized beams at the lowest order. In order to investigate the observability, we display some typical final state distributions in the Higgs to diphoton channel.
• Select
  Wilsonian Renormalization Group and the Lippmann-Schwinger Equation with a Multitude of Cutoff Parameters

  E. Epelbaum, J. Gegelia, Ulf-G. Meißner

  理论物理通讯. 2018, 69(03): 303-307.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  The Wilsonian renormalization group approach to the Lippmann-Schwinger equation with a multitude of cutoff parameters is introduced. A system of integro-differential equations for the cutoff-dependent potential is obtained. As an illustration, a perturbative solution of these equations with two cutoff parameters for a simple case of an S-wave low-energy potential in the form of a Taylor series in momenta is obtained. The relevance of the obtained results for the effective field theory approach to nucleon-nucleon scattering is discussed.
• Select
  Application of Connection in Molecular Dynamics

  孙鑫

  理论物理通讯. 2018, 69(03): 308-310.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  The evolution of electronic states in molecule has two origins:dynamical one produced by Schrödinger equation and kinematical one caused by base transformation due to nuclear motion. In current theories, the former gets analytic expression; the latter depends on heavy numerical calculation, which contains uncertainty. By using connection of fiber bundles, this paper establishes an analytic formula for the latter, and the numerical work is simplified. It shows the mathematical structure of molecule is fiber bundle.
• Select
  Decoherence Effect and Beam Splitters for Production of Quasi-Amplified Entangled Quantum Optical Light

  Saad Rfifi

  理论物理通讯. 2018, 69(03): 311-316.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  We let a set of beam splitters of vacuum mode with a chosen transmittance parameter η in interaction with a separable coherent states. This model induces the production of an attenuated quantum channels based on entangled optical states. Indeed, the decoherence effect is exploited positively here to generate such kind of quantum channels. Next, the amplitude damping and the entanglement amount of these produced channels are enhanced thereafter by a probabilistic quasi amplification process using again a 50:50 beam splitter.
• Select
  Thermally Radiative Rotating Magneto-Nanofluid Flow over an Exponential Sheet with Heat Generation and Viscous Dissipation: A Comparative Study

  M. Sagheer, M. Bilal, S. Hussain, R. N. Ahmed

  理论物理通讯. 2018, 69(03): 317-328.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  This article examines a mathematical model to analyze the rotating flow of three-dimensional water based nanofluid over a convectively heated exponentially stretching sheet in the presence of transverse magnetic field with additional effects of thermal radiation, Joule heating and viscous dissipation. Silver (Ag), copper (Cu), copper oxide (CuO), aluminum oxide (Al₂O₃) and titanium dioxide (TiO₂) have been taken under consideration as the nanoparticles and water (H₂O) as the base fluid. Using suitable similarity transformations, the governing partial differential equations (PDEs) of the modeled problem are transformed to the ordinary differential equations (ODEs). These ODEs are then solved numerically by applying the shooting method. For the particular situation, the results are compared with the available literature. The effects of different nanoparticles on the temperature distribution are also discussed graphically and numerically. It is witnessed that the skin friction coefficient is maximum for silver based nanofluid. Also, the velocity profile is found to diminish for the increasing values of the magnetic parameter.
• Select
  Cole-Hopf Transformation Based Lattice Boltzmann Model for One-dimensional Burgers' Equation

  亓晓同, 施保昌, 柴振华

  理论物理通讯. 2018, 69(03): 329-335.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  In this paper, we present a Cole-Hopf transformation based lattice Boltzmann (LB) model for solving one-dimensional Burgers' equation, and compared to available LB models, the effect of nonlinear convection term can be eliminated. Through Chapman-Enskog analysis, it can be found that the converted diffusion equation based on the Cole-Hopf transformation can be recovered correctly from present LB model. Some numerical tests are also performed to validate the present LB model, and the numerical results show that, similar to previous LB models, the present model also has a second-order convergence rate in space, but it is more accurate than the previous ones.
• Select
  A First-Principles Study on the Vibrational and Electronic Properties of Zr-C MXenes

  王昌英, 郭永亮, 赵媛媛, 曾广礼, 张伟, 任翠兰, 韩晗, 怀平

  理论物理通讯. 2018, 69(03): 336-342.

  摘要 ( ) PDF全文 ( )   可视化   收藏

  Within the framework of density functional theory calculations, the structural, vibrational, and electronic properties of Zr_nC_n-1 (n=2, 3, and 4) and their functionalized MXenes have been investigated. We find that the most stable configurations for Zr-C MXene are the ones that the terminal groups F, O, and OH locate on the common hollow site of the superficial Zr layer and its adjacent C layer. F and OH-terminated Zr₃C₂ and Zr₄C₃ have small imaginary acoustic phonon branches around Γ point while the others have no negative phonon modes. The pristine MXenes (Zr₂C, Zr₃C₂ and Zr₄C₃) are all metallic with large DOS contributed by the Zr atom at the Fermi energy. When functionalized by F, O and OH, new hybridization states appear and the DOS at the Fermi level are reduced. Moreover, we find that their metallic characteristic increases with an increase in n. For (Zr_nC_n-1)O₂, Zr₂CO₂ is a semiconductor, Zr₃C₂O₂ is a semimetal, and Zr₄C₃O₂ becomes a metal.