2017年, 第67卷, 第02期　
刊出日期：2017-02-01

  

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  Algebraic Structure of Discrete Zero Curvature Equations and Master Symmetries of Discrete Evolution Equations

  罗琳

  理论物理通讯. 2017, 67(02): 127-130.

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  In this paper, based on a discrete spectral problem and the corresponding zero curvature representation, the isospectral and nonisospectral lattice hierarchies are proposed. An algebraic structure of discrete zero curvature equations is then established for such integrable systems. the commutation relations of Lax operators corresponding to the isospectral and non-isospectral lattice flows are worked out, the master symmetries of each lattice equation in the isospectral hierarchyand are generated, thus a τ-symmetry algebra for the lattice integrable systems is engendered from this theory.
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  Lax Triad Approach to Symmetries of Scalar Modified Kadomtsev-Petviashvili Hierarchy

  邓潇, 陈奎, 张大军

  理论物理通讯. 2017, 67(02): 131-136.

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  By means of Lax triads we reconstruct isospectral and nonisospectral scalar modified Kadomtsev-Petviashvili (mKP) hierarchies. In this approach the argument y is treated as an independent variable which is independent of time parameters {t₁, t₂,…}. Consequently, the isospectral and nonisospectral scalar mKP flows can have clear zero curvature representations, which enables us to handle investigation of symmetries of the scalar isospectral mKP hierarchy as freely as for (1+1)-dimensional systems. As a result, we obtain Lie algebraic structures of the scalar mKP flows and construct symmetries for the scalar isospectral mKP hierarchy.
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  Finite-Time Stability for Fractional-Order Bidirectional Associative Memory Neural Networks with Time Delays

  徐昌进, 李培峦, 庞一成

  理论物理通讯. 2017, 67(02): 137-142.

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  This paper is concerned with fractional-order bidirectional associative memory (BAM) neural networks with time delays. Applying Laplace transform, the generalized Gronwall inequality and estimates of Mittag-Leffler functions, some sufficient conditions which ensure the finite-time stability of fractional-order bidirectional associative memory neural networks with time delays are obtained. Two examples with their simulations are given to illustrate the theoretical findings. Our results are new and complement previously known results.
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  Nonlocal Symmetry, CTE Solvability and Interaction Solutions of Whitham-Broer-Kaup Equations

  周伟, 陆斌

  理论物理通讯. 2017, 67(02): 143-146.

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  Whitham-Broer-Kaup (WBK) equations in the shallow water small-amplitude regime is hereby under investigation. Nonlocal symmetry and Bäcklund transformation are presented via the truncated Painlevé expansion. This residual symmetry is localised to Lie point symmetry by the properly enlarged system. The finite symmetry transformation of the prolonged system is computed. Based on the CTE method, WBK equations are linearized and new analytic interaction solutions between solitary waves and cnoidal waves are given with the aid of solutions for the linear equation.
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  Quantum Private Comparison via Cavity QED

  叶天语

  理论物理通讯. 2017, 67(02): 147-156.

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  The first quantum private comparison (QPC) protocol via cavity quantum electrodynamics (QED) is proposed in this paper by making full use of the evolution law of atom via cavity QED, where the third party (TP) is allowed to misbehave on his own but cannot conspire with either of the two users. The proposed protocol adopts two-atom product states rather than entangled states as the initial quantum resource, and only needs single-atom measurements for two users. Both the unitary operations and the quantum entanglement swapping operation are not necessary for the proposed protocol. The proposed protocol can compare the equality of one bit from each user in each round comparison with one two-atom product state. The proposed protocol can resist both the outside attack and the participant attack. Particularly, it can prevent TP from knowing two users' secrets. Furthermore, the qubit efficiency of the proposed protocol is as high as 50%.
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  Lie Symmetries, Conservation Laws and Explicit Solutions for Time Fractional Rosenau-Haynam Equation

  秦春艳, 田守富, 王秀彬, 张田田

  理论物理通讯. 2017, 67(02): 157-165.

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  Under investigation in this paper is the invariance properties of the time fractional Rosenau-Haynam equation, which can be used to describe the formation of patterns in liquid drops. By using the Lie group analysis method, the vector fields and symmetry reductions of the equation are derived, respectively. Moreover, based on the power series theory, a kind of explicit power series solutions for the equation are well constructed with a detailed derivation. Finally, by using the new conservation theorem, two kinds of conservation laws of the equation are well constructed with a detailed derivation.
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  Estimation on Geometric Measure of Quantum Coherence

  张海军, 陈斌, 李明, 费少明, 龙桂鲁

  理论物理通讯. 2017, 67(02): 166-170.

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  We study the geometric measure of quantum coherence recently proposed in [Phys. Rev. Lett. 115 (2015) 020403]. Both lower and upper bounds of this measure are provided. These bounds are shown to be tight for a class of important coherent states-maximally coherent mixed states. The trade-off relation between quantum coherence and mixedness for this measure is also discussed.
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  Strong Analog Classical Simulation of Coherent Quantum Dynamics

  王东升

  理论物理通讯. 2017, 67(02): 171-181.

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  A strong analog classical simulation of general quantum evolution is proposed, which serves as a novel scheme in quantum computation and simulation. The scheme employs the approach of geometric quantum mechanics and quantum informational technique of quantum tomography, which applies broadly to cases of mixed states, nonunitary evolution, and infinite dimensional systems. The simulation provides an intriguing classical picture to probe quantum phenomena, namely, a coherent quantum dynamics can be viewed as a globally constrained classical Hamiltonian dynamics of a collection of coupled particles or strings. Efficiency analysis reveals a fundamental difference between the locality in real space and locality in Hilbert space, the latter enables efficient strong analog classical simulations. Examples are also studied to highlight the differences and gaps among various simulation methods.
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  Dark Soliton Solutions of Space-Time Fractional Sharma-Tasso-Olver and Potential Kadomtsev-Petviashvili Equations

  Ozkan Guner, Alper Korkmaz, Ahmet Bekir

  理论物理通讯. 2017, 67(02): 182-188.

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  Dark soliton solutions for space-time fractional Sharma-Tasso-Olver and space-time fractional potential Kadomtsev-Petviashvili equations are determined by using the properties of modified Riemann-Liouville derivative and fractional complex transform. After reducing both equations to nonlinear ODEs with constant coefficients, the tanh ansatz is substituted into the resultant nonlinear ODEs. The coefficients of the solutions in the ansatz are calculated by algebraic computer computations. Two different solutions are obtained for the Sharma-Tasso-Olver equation as only one solution for the potential Kadomtsev-Petviashvili equation. The solution profiles are demonstrated in 3D plots in finite domains of time and space.
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  Closed Timelike Curves in Type Ⅱ Non-Vacuum Spacetime

  Faizuddin Ahmed

  理论物理通讯. 2017, 67(02): 189-191.

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  Here we present a cyclicly symmetric non-vacuum spacetime, admitting closed timelike curves (CTCs) which appear after a certain instant of time, i.e., a time-machine spacetime. The spacetime is asymptotically flat, freefrom curvature singularities and a four-dimensional extension of the Misner space in curved spacetime. The spacetime is of type Ⅱ in the Petrov classification scheme and the matter field pure radiation satisfy the energy condition.
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  Metastability in the Spin-1 Blume-Emery-Griffiths Model within Constant Coupling Approximation

  C. Ekiz

  理论物理通讯. 2017, 67(02): 192-196.

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  In this paper, the equilibrium properties of spin-1 Blume-Emery-Griffiths model are studied by using constant-coupling approximation. The dipolar and quadrupolar order parameters, the stable, metastable and unstable states and free energy of the model are investigated. The states are defined in terms of local minima of the free energy of system. The numerical calculations are presented for several values of exchange interactions on the simple cubic lattice with q=6.
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  New Exact Solutions for the Wick-Type Stochastic Kudryashov-Sinelshchikov Equation

  S. Saha Ray, S. Singh

  理论物理通讯. 2017, 67(02): 197-206.

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  In this article, exact solutions of Wick-type stochastic Kudryashov-Sinelshchikov equation have been obtained by using improved Sub-equation method. We have used Hermite transform for transforming the Wick-type stochastic Kudryashov-Sinelshchikov equation to deterministic partial differential equation. Also we have applied inverse Hermite transform for obtaining a set of stochastic solutions in the white noise space.
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  Solitary Wave Solutions of KP equation, Cylindrical KP Equation and Spherical KP Equation

  李向正, 张金良, 王明亮

  理论物理通讯. 2017, 67(02): 207-211.

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  Three (2+1)-dimensional equations-KP equation, cylindrical KP equation and spherical KP equation, have been reduced to the same KdV equation by different transformation of variables respectively. Since the single solitary wave solution and 2-solitary wave solution of the KdV equation have been known already, substituting the solutions of the KdV equation into the corresponding transformation of variables respectively, the single and 2-solitary wave solutions of the three (2+1)-dimensional equations can be obtained successfully.
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  Inclusive Cross Section Production of J/ψ in LEP

  T. Osati, B. Abubakri

  理论物理通讯. 2017, 67(02): 212-216.

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  Cross section production is one of the observable quantities in the hadronic systems. Inclusive cross section production J/ψ may be calculated through the use of the fragmentation c→J/ψ. In this paper we calculate the inclusive cross section production J/ψ about the pole of Z⁰ in the e⁺e^- annihilation, through the lowest order regim of perturbative of QCD ananlyticaly. The obtained results arrive an excellent agreement with the exprimental data to produce the inclusive cross section production c→J/ψ.
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  Mixture of Electromagnetically Induced Transparency and Autler-Townes Splitting in a Five-Level Atomic System

  张晓芸, 吴山, 李海超

  理论物理通讯. 2017, 67(02): 217-221.

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  Discerning electromagnetically induced transparency (EIT) from Autler-Townes splitting (ATS) is a significant issue in quantum optics and has attracted wide attention in various three-level configurations. Here we present a detailed study of EIT and ATS in a five-level atomic system considered to be composed of a four-level Y-type subsystem and a three-level Λ-type subsystem. In our theoretical calculations with standard density matrix formalism and steadystate approximation, we obtain the general analytical expression of the first-order matrix element responsible for the probe-field absorption. In light of the well-known three-level EIT and ATS criteria, we numerically show an intersection of EIT with ATS for the Y-type subsystem. Furthermore, we show that an EIT dip is sandwiched between two ATS dips (i.e., multi-dip mixture of EIT and ATS) in the absorption line for the five-level system, which can be explained by the dressed-state theory and Fano interference.
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  Anisotropic Bianchi Type I Cosmological Models with Generalized Chaplygin Gas and Dynamical Gravitational and Cosmological Constants

  S. Kotambkar, G. P. Singh, R. Kelkar, Binaya K. Bishi

  理论物理通讯. 2017, 67(02): 222-230.

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  This paper deals with study of generalized Chaplygin gas model with dynamical gravitational and cosmological constants. In this paper a new set of exact solutions of Einstein field equations for spatially homogeneous and anisotropic Bianchi type I space-time have been obtained. The solutions of the Einstein's field equations are obtained by considering (i) the power law relation between Hubble parameter H and scale factor R and (ii) scale factor of the form R=-1/t+t², t>1. The assumptions lead to constant and variable deceleration parameter respectively. The physical and dynamical behaviors of the models have been discussed with the help of graphical representations. Also we have discussed the stability and physical acceptability of solutions for solution type-I and solution type-Ⅱ.