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Most Downloaded Physics Letters A Articles
The N-soliton solution of a two-component modified nonlinear Schrödinger equation
8 August 2011
Yoshimasa Matsuno
The N-soliton solution is presented for a two-component modified nonlinear Schrödinger equation which describes the propagation of short pulses in birefringent optical fibers. The solution is found to be expressed in terms of determinants. The proof of the solution is carried out by means of an elementary theory of determinants. The generalization of the 2-component system to the multi-component system is discussed as well as a (2+1)-dimensional nonlocal equation arising from its continuum limit.
Compacton and solitary pattern solutions for nonlinear dispersive KdV-type equations involving Jumarieʼs fractional derivative
2 January 2012
Shimin Guo | Liquan Mei | Ye Fang | Zhiyu Qiu
In this Letter, the fractional variational iteration method using Heʼs polynomials is implemented to construct compacton solutions and solitary pattern solutions of nonlinear time-fractional dispersive KdV-type equations involving Jumarieʼs modified Riemann–Liouville derivative. The method yields solutions in the forms of convergent series with easily calculable terms. The obtained results show that the considered method is quite effective, promising and convenient for solving fractional nonlinear dispersive equations. It is found that the time-fractional parameter significantly changes the soliton amplitude of the solitary waves.
Multiscale modeling of graphene- and nanotube-based reinforced polymer nanocomposites
31 October 2011
A. Montazeri | H. Rafii-Tabar
A combination of molecular dynamics, molecular structural mechanics, and finite element method is employed to compute the elastic constants of a polymeric nanocomposite embedded with graphene sheets, and carbon nanotubes. The model is first applied to study the effect of inclusion of graphene sheets on the Young modulus of the composite. To explore the significance of the nanofiller geometry, the elastic constants of nanotube-based and graphene-based polymer composites are computed under identical conditions. The reinforcement role of these nanofillers is also investigated in transverse directions. Moreover, the dependence of the nanocompositeʼs axial Young modulus on the presence of ripples on the surface of the embedded graphene sheets, due to thermal fluctuations, is examined via MD simulations. Finally, we have also studied the effect of sliding motion of graphene layers on the elastic constants of the nanocomposite.
Asymmetric optical mode conversion and transmission by breaking PT-symmetry on silicon photonic circuits
30 January 2012
Ye-Long Xu | Liang Feng | Ming-Hui Lu | Yan-Feng Chen
Asymmetric propagation of electromagnetic or elastic waves is important for control of the signal flow in various devices. Through mutual consistent theory analysis and numerical simulations to discuss the parity–time (PT) symmetry, we proposed and studied a linear silicon photonic device that shows asymmetric optical mode conversion. Remarkably, unidirectional mode conversion is observed at the threshold of breaking of the PT symmetry of our system. The corresponding theoretical analysis is expected to help design of chip-scale directional photonic devices.
Staggered car-following induced by lateral separation effects in traffic flow
2 January 2012
Sheng Jin | Dian-hai Wang | Cheng Xu | Zhi-yi Huang
This Letter develops a new staggered car-following model taking into consideration lateral separation effects. Time-to-collision, calculated using visual angle variables, is introduced to describe the lateral separation distance and improve the optimal velocity model. The analytical and numerical results show that the stability of traffic flow can gradually be enhanced with the increase of lateral separation effects. The asymmetry property of traffic flow is also investigated using the new model. The results imply that incorporating lateral separation effects into the car-following model leads to the suppression of traffic jams and greatly enhances the realism of the model.
Nonlocal plate model for free vibrations of single-layered graphene sheets
15 November 2010
R. Ansari | S. Sahmani | B. Arash
Vibration analysis of single-layered graphene sheets (SLGSs) is investigated using nonlocal continuum plate model. To this end, Eringens's nonlocal elasticity equations are incorporated into the classical Mindlin plate theory for vibrations of rectangular nanoplates. In contrast to the classical model, the nonlocal model developed in this study has the capability to evaluate the natural frequencies of the graphene sheets with considering the size-effects on the vibrational characteristics of them. Solutions for frequencies of the free vibration of simply-supported and clamped SLGSs are computed using generalized differential quadrature (GDQ) method. Then, molecular dynamics (MD) simulations for the free vibration of various SLGSs with different values of side length and chirality are employed, the results of which are matched with the nonlocal model ones to derive the appropriate values of the nonlocal parameter relevant to each boundary condition. It is found that the value of the nonlocal parameter is independent of the magnitude of the geometrical variables of the system.
A feasible approach to achieve acoustic carpet cloak in air
9 January 2012
Xiao-Liu Zhang | Xu Ni | Ming-Hui Lu | Yan-Feng Chen
A type of acoustic carpet cloak has been theoretically designed and numerically implemented in air using steel/air composites. By using the effective medium theory, the effective density and bulk modulus of the composite material are designed to agree with the spatially variant parameters calculated from the coordinate transformation approach. Great cloaking performance is achieved as an object is well hidden under a sound reflective surface in a wide frequency range. It has also been shown that sound can be effectively manipulated using the proposed composite materials because of its low complexity.
Dynamical behaviors of a chaotic system with no equilibria
5 December 2011
Zhouchao Wei
Based on Sprott D system, a simple three-dimensional autonomous system with no equilibria is reported. The remarkable particularity of the system is that there exists a constant controller, which can adjust the type of chaotic attractors. It is demonstrated to be chaotic in the sense of having a positive largest Lyapunov exponent and fractional dimension. To further understand the complex dynamics of the system, some basic properties such as Lyapunov exponents, bifurcation diagram, Poincaré mapping and period-doubling route to chaos are analyzed with careful numerical simulations.
The difference between Schrödinger equation derived from Schrödinger map and Landau–Lifshitz equation
9 January 2012
Ganshan Yang
We provide an explicit blow up solution of Schrödinger equation derived from Schrödinger map. Consequently we show the non-equivalence between the Schrödinger equation and Landau–Lifshitz equation. We also find that two class of equivariant solutions of Landau–Lifshitz equation are static.
Spontaneous emission enhancement in metal–dielectric metamaterials
2 January 2012
Ivan Iorsh | Alexander Poddubny | Alexey Orlov | Pavel Belov | Yuri S. Kivshar
We study the spontaneous emission of a dipole emitter imbedded into a layered metal–dielectric metamaterial. We demonstrate ultra-high values of the Purcell factor in such structures due to a high density of states with hyperbolic isofrequency surfaces. We reveal that the traditional effective-medium approach greatly underestimates the value of the Purcell factor due to the presence of an effective nonlocality, and we present an analytical model which agrees well with numerical calculations.
Efficient three-to-one entanglement purification protocol
2 January 2012
Dong Pyo Chi | Taewan Kim | Soojoon Lee
We present a new entanglement purification protocol on three copies of a state via two bilateral controlled-NOT operations. We show that one-round successful probability of our protocol is twice as large as that of the protocol by Feng et al. [Phys. Lett. A 271 (2000) 44], [8], and that our method can be applied to the existing best protocol so as to improve the efficiency.
Geometrical explanation of the fractional complex transform and derivative chain rule for fractional calculus
9 January 2012
Ji-Huan He | S.K. Elagan | Z.B. Li
The fractional complex transform is suggested to convert a fractional differential equation with Jumarieʼs modification of Riemann–Liouville derivative into its classical differential partner. Understanding the fractional complex transform and the chain rule for fractional calculus are elucidated geometrically.
Enhanced Kerr nonlinearity via quantum interference from spontaneous emission
2 January 2012
S.H. Asadpour | M. Sahrai | A. Soltani | H.R. Hamedi
A novel atom configuration is proposed for a giant Kerr nonlinearity in zero linear and nonlinear probe absorption. It is shown that without coherent control field and just by quantum interference of spontaneous emission, a giant Kerr nonlinearity can be obtained.
Significant thermal conductivity enhancement for nanofluids containing graphene nanosheets
7 March 2011
Wei Yu | Huaqing Xie | Xiaoping Wang | Xinwei Wang
We developed a facile technique to produce ethylene glycol based nanofluids containing graphene nanosheets. The thermal conductivity of the base fluid was increased significantly by the dispersed graphene: up to 86% increase for 5.0 vol % graphene dispersion. The 2D structure and stiffness of graphene and graphene oxide help to increase the thermal conductivity of the nanofluid. The thermal conductivity of graphene oxide and graphene in the fluid were estimated to be ∼4.9 and 6.8 W/m K, respectively.
Acoustic metamaterial with negative density
7 December 2009
Sam Hyeon Lee | Choon Mahn Park | Yong Mun Seo | Zhi Guo Wang | Chul Koo Kim
We fabricated a one-dimensional acoustic metamaterial with negative effective density using an array of very thin elastic membranes. We observed acoustic equivalence of the plasma oscillation at ωc=735 Hz. The metamaterial was opaque in the frequency range from 0 to 735 Hz, and was transparent above 735 Hz. We report direct observation of negative acceleration in this acoustic medium below 735 Hz. The frequency characteristics of the metamaterial have the same form as that of metals with negative permittivity. We also provide a simple theory to explain the experimental results.
Correlation dynamics of qubit–qutrit systems in a classical dephasing environment
14 November 2011
G. Karpat | Z. Gedik
We study the time evolution of classical and quantum correlations for hybrid qubit–qutrit systems in independent and common dephasing environments. Our discussion involves a comparative analysis of the Markovian dynamics of negativity, quantum discord, geometric measure of quantum discord and classical correlation. For the case of independent environments, we have demonstrated the phenomenon of sudden transition between classical and quantum decoherence for qubit–qutrit states. In the common environment case, we have shown that dynamics of quantum and geometric discords might be completely independent of each other for a certain time interval, although they tend to be eventually in accord.
Vector financial rogue waves
21 November 2011
Zhenya Yan
The coupled nonlinear volatility and option pricing model presented recently by Ivancevic is investigated, which generates a leverage effect, i.e., stock volatility is (negatively) correlated to stock returns, and can be regarded as a coupled nonlinear wave alternative of the Black–Scholes option pricing model. In this Letter, we analytically propose vector financial rogue waves of the coupled nonlinear volatility and option pricing model without an embedded w-learning. Moreover, we exhibit their dynamical behaviors for chosen different parameters. The vector financial rogue wave (rogon) solutions may be used to describe the possible physical mechanisms for the rogue wave phenomena and to further excite the possibility of relative researches and potential applications of vector rogue waves in the financial markets and other related fields.
Non-Hermitian oscillator Hamiltonians and multiple Charlier polynomials
5 December 2011
Hiroshi Miki | Luc Vinet | Alexei Zhedanov
A set of r non-Hermitian oscillator Hamiltonians in r dimensions is shown to be simultaneously diagonalizable. Their spectra are real and the common eigenstates are expressed in terms of multiple Charlier polynomials. An algebraic interpretation of these polynomials is thus achieved and the model is used to derive some of their properties.
Electronic properties of boron and nitrogen doped graphene nanoribbons and its application for graphene electronics
24 January 2011
Bing Huang
On the basis of density functional theory calculations, we have systematically investigated the electronic properties of armchair-edge graphene nanoribbons (GNRs) doped with boron (B) and nitrogen (N) atoms. B (N) atoms could effectively introduce holes (electrons) to GNRs and the system exhibits p- (n-) type semiconducting behavior after B (N) doping. According to the electronic structure calculations, Z-shape GNR-based field effect transistors (FETs) is constructed by selective doping with B or N atoms. Using first-principles quantum transport calculations, we demonstrate that the B-doped p-type GNR-FETs can exhibit high levels of performance, with high ON/OFF ratios and low subthreshold swing. Furthermore, the performance parameters of GNR-FETs could be controlled by the p-type semiconducting channel length.
Electronic structure tuning and band gap opening of graphene by hole/electron codoping
24 October 2011
Xiaohui Deng | Yanqun Wu | Jiayu Dai | Dongdong Kang | Dengyu Zhang
A pathway to open the band gap of graphene by p–n codoping is presented according to the first principles study. Two models are used: Lithium adsorbed on Boron-doped graphene (BG) and Boron–Nitrogen (B/N) codoping into graphene. The stability of Lithium adsorbed on BG is firstly analyzed, showing that the hollow site is the most stable configuration, and there is no energy barrier from some metastable configurations to a stable one. After the p–n codoping, the electronic structures of graphene are modulated to open a band gap with width from 0.0 eV to 0.49 eV, depending on the codoping configurations. The intrinsic physical mechanism responsible for the gap opening is the combination of the Boron atom acting as hole doping and Nitrogen (Lithium) as electron doping.
Optimal local transformations of flip and exchange symmetric entangled states
5 December 2011
G. Karpat | Z. Gedik
Local quantum operations relating multiqubit flip (0–1) and exchange symmetric (FES) states, with the maximum possible probability of success, have been determined by assuming that the states are converted via one-shot FES transformations. It has been shown that certain entangled states are more robust than others, in the sense that the optimum probability of converting these robust states to the states lying in the close neighborhood of separable ones vanish under local FES operations.
First-principles study of the structural, magnetic, and electronic properties of LiMBO3 (M=Mn, Fe, Co)
2 January 2012
Zhiping Lin | Yu-Jun Zhao | Yanming Zhao
We present a first-principles calculation for the structural, magnetic, and electronic properties of LiMBO3 (M=Mn, Fe, Co). Along the [0 0 1] direction, transition metals shows antiferromagnetic coupling in LiMBO3 of both hexagonal and monoclinic lattices. The calculated magnetic moment of 5μB per formula unit is close to the experimental value. These compounds are semiconductors with band gap of 0.4–2 eV, and with average intercalation voltages of 2–4.8 V.
Physical content of Heisenberg's uncertainty relation: limitation and reformulation
3 November 2003
Masanao Ozawa
Heisenberg's reciprocal relation between position measurement error and momentum disturbance is rigorously proven under the assumption that those error and disturbance are independent of the state of the measured object. A generalization of Heisenberg's relation proven valid for arbitrary measurements is proposed and reveals two distinct types of possible violations of Heisenberg's relation.
Renormalization group analysis of the small-world network model
6 December 1999
M.E.J. Newman | D.J. Watts
We study the small-world network model, which mimics the transition between regular-lattice and random-lattice behavior in social networks of increasing size. We contend that the model displays a critical point with a divergent characteristic length as the degree of randomness tends to zero. We propose a real-space renormalization group transformation for the model and demonstrate that the transformation is exact in the limit of large system size. We use this result to calculate the exact value of the single critical exponent for the system, and to derive the scaling form for the average number of `degrees of separation' between two nodes on the network as a function of the three independent variables. We confirm our results by extensive numerical simulation.
Dust density effect on complex plasma decay
4 August 2008
L. Couëdel | A.A. Samarian | M. Mikikian | L. Boufendi
In this Letter, the influence of dust particles on the plasma losses in a complex plasma afterglow is studied. It is shown that the dust particles can drastically shorten the plasma loss time by absorption-recombination onto their surfaces. The dust particle absorption frequency increases with the dust density but the dependence is not linear for high dust density. Finally, the possible use of dust absorption frequency measurements as a diagnostic for complex plasmas is mentioned and supported by comparison to existing experimental data.
