Linear and nonlinear electromagnetic waves in modulated honeycomb media

Wave dynamics in topological materials has been widely studied recently. A striking feature is the existence of robust and chiral wave propagations that have potential applications in many fields. A common way to realize such wave patterns is to utilize Dirac points, which carry topological indices and is supported by the symmetries of the media. In this work, we investigate these phenomena in photonic media. Starting with Maxwell's equations with a honeycomb material weight as well as the nonlinear Kerr effect, we first prove the existence of Dirac points in the dispersion surfaces of transverse electric and magnetic Maxwell operators under very general assumptions of the material weight. Our assumptions on the material weight are almost the minimal requirements to ensure the existence of Dirac points in a general hexagonal photonic crystal. We then derive the associated wave packet dynamics in the scenario where the honeycomb structure is weakly modulated. It turns out the reduced envelope equation is generally a two-dimensional nonlinear Dirac equation with a spatially varying mass. By studying the reduced envelope equation with a domain-wall-like mass term, we realize the subtle wave motions, which are chiral and immune to local defects. The underlying mechanism is the existence of topologically protected linear line modes, also referred to as edge states. However, we show that these robust linear modes do not survive with nonlinearity. We demonstrate the existence of nonlinear line modes, which can propagate in the nonlinear media based on high-accuracy numerical computations. Moreover, we also report a new type of nonlinear modes, which are localized in both directions.     

Propagation of nonlinear magnetoacoustic waves in a compressible medium of finite electrical conductivity

We study the one-dimensional propagation of weakly nonlinear waves in a compressible medium of finite electrical conductivity subjected to the action of a magnetic field. We obtain evolution equations that describe the wave processes under small and finite magnetic Reynolds numbers. It is shown that in a medium of finite conductivity the evolution of perturbations in a fluid is described by the modified Bürger's equation. We find the stationary and automodel solution of this equation and use them as the basis for analyzing the influence of effects of electrical conductivity on the structure of weak shock waves.Translated fromMatematicheskie Metody i Fiziko-Mekhanicheskie Polya, Issue 32, 1990, pp. 73–76.     

On the propagation of nonlinear solitary waves in a distributed Schottky barrier diode transmission line

A nonlinear distributed Schottky barrier diode is analyzed and it is found to be similar to a 3-component quasi-neutral plasma consisting of negative ions and electrons that are neutralized with positive ions. In such a plasma, it has been shown that both KdV and mKdV solitons can exist. We obtain the criteria for the distributed Schottky barrier diode that will permit the propagation of both KdV and mKdV solitary waves.     

Nonlinear supratransmission in a discrete nonlinear electrical transmission line: Modulated gap peak solitons

We examine the propagation conditions of modulated gap signal voltage in a one-dimensional nonlinear discrete electrical transmission line where nonlinear capacitors are introduced both in their series and shunt branches. Especially, we consider that the propagating signal voltage frequency belong to the forbidden band zones. Using the exact discrete equations of the network and the extended nonlinear Schrödinger equation, the threshold value of the signal amplitude over which pulse soliton is emitted in the network is found. We show that when the signal amplitude exceeds a particular value, the critical value, peaked soliton can be emitted by the network due to the nonlinear dispersive elements of the series branches. Numerical simulations, confirming the exactness of the analytical analysis are performed on the exact equations of the network.     

Exact traveling discrete kink-soliton solutions for the discrete nonlinear electrical transmission lines

We investigate exact soliton solutions for the discrete nonlinear electrical transmission line by performing the simplest equation method from a trivial seed solution. Starting from the nonlinear propagation of signals in electrical transmission lines, we derive exact traveling kink and antikink solitary wave solutions. It is shown that under a safe range of parameter, the shape of kink soliton can be controlled well by adjusting the parameter of the line. The analytical solutions for the kink and antikink solitary waves are tested in direct simulations.     

Solitary waves in a quartic nonlinear elastic rod

The bright and dark solitons described by the nonlinear Schrödinger equation (NLSE) are given for a quartic nonlinear elastic rod. It has also been found that the KdV soliton does not exist in this system.     

Propagation of electromagnetic waves in a nonlinear dielectric slab

The early phases of propagation of a large amplitude electromagnetic disturbance in a nonlinear dielectric slab embedded between two linear media are investigated by the method of characteristics. This disturbance is triggered by the arrival of an electromagnetic shock wave at one of the interfaces. Reflection and transmission of an arbitrary signal when it arrives at one of the slab boundaries is characterized in terms of nonlinear reflection and transmission coefficients for the interface. No restrictions are placed on the form of the constitutive laws of the material comprising the slab. By introducing, for the nonlinear dielectric, a class of model equations, an exact solution to the characteristic equations which describes the interaction of a centered wave with anarbitrary oncoming signal is obtained. Solutions for the electromagnetic fields are derived for the special case in which the incident disturbance interacts with the reflected signal from the slab interface. A particular case of the disturbance propagating across a nonmagnetic slab is also examined.     

Interactions of nonlinear ion-acoustic waves in a collisionless plasma

In the present work, based on a one-dimensional model, the interaction of two solitary waves propagating in opposite directions in a collisionless plasma is investigated by use of the extended Poincaré–Lighthill–Kuo (PLK) method. It is shown that bi-directional solitary waves are propagated and the head-on collision of these two solitons occur. The phase shifts and the trajectories of these two solitons after the collision are obtained.     

Propagation of TM waves in a Kerr nonlinear layer

TM electromagnetic waves propagating through a nonlinear homogeneous isotropic unmagnetized dielectric layer located between two homogeneous isotropic half-spaces are studied. The nonlinearity in the layer obeys the Kerr law. The problem is reduced to a system of nonlinear ordinary differential equations. A dispersion relation for the propagation constants is derived. The results are compared with those in the case of a linear layer.     

Generation of linear and nonlinear waves in numerical wave tank using clustering technique-volume of fluid method

A two-dimensional (2D) numerical model is developed for the wave simulation and propagation in a wave flume.The fluid flow is assumed to be viscous and incompressible,and the Navier-Stokes and continui...     

Existence of travelling waves in a modified vector-disease model

In this paper, we consider travelling wave solutions for a modified vector-disease model. Special attention is paid to the model in which a susceptible vector can receive the infection not only from the infectious host but also from the infectious vector. For the strong generic delay kernel, we show that travelling wave solutions exist using the geometric singular perturbation theory.     

Importance sampling for a Markov modulated queuing network

Importance sampling (IS) is a variance reduction method for simulating rare events. A recent paper by Dupuis, Wang and Sezer [Paul Dupuis, Ali Devin Sezer, Hui Wang, Dynamic importance sampling for queueing networks, Annals of Applied Probability 17 (4) (2007) 1306–1346] exploits connections between IS and stochastic games and optimal control problems to show how to design and analyze simple and efficient IS algorithms for various overflow events of tandem Jackson Networks. The present paper carries out a program parallel to the paper by Dupuis et al. for a two node tandem network whose arrival and service rates are modulated by an exogenous finite state Markov process. The overflow event we study is the following: the number of customers in the system reaches n$n$ without the system ever becoming empty, given that initially the system is empty.     

Extreme wave phenomena in down-stream running modulated waves

Modulational, Benjamin-Feir, instability is studied for the down-stream evolution of surface gravity waves. An explicit solution, the soliton on finite background, of the NLS equation in physical space is used to study various phenomena in detail. It is shown that for sufficiently long modulation lengths, at a unique position where the largest waves appear, phase singularities are present in the time signal. These singularities are related to wave dislocations and lead to a discrimination between successive ‘extreme’ waves and much smaller intermittent waves. Energy flow in opposite directions through successive dislocations at which waves merge and split, causes the large amplitude difference. The envelope of the time signal at that point is shown to have a simple phase plane representation, and will be described by a symmetry breaking unfolding of the steady state solutions of NLS. The results are used together with the maximal temporal amplitude MTA, to design a strategy for the generation of extreme (freak, rogue) waves in hydrodynamic laboratories.     

A nonlinear boundary eigenvalue problem for TM-polarized electromagnetic waves in a nonlinear layer

We consider the propagation of TM-polarized electromagnetic waves in a nonlinear dielectric layer located between two linear media. The nonlinearity in the layer is described by the Kerr law. We reduce the problem to a nonlinear boundary eigenvalue problem for a system of ordinary differential equations. We obtain a dispersion relation and a first approximation for eigenvalues of the problem. We compare the results with those obtained for the case of a linear medium in the layer.     

The method of cauchy problem for solving a nonlinear eigenvalue transmission problem for tm waves propagating in a layer with arbitrary nonlinearity

The problem of plane monochromatic TM waves propagating in a layer with an arbitrary nonlinearity is considered. The layer is placed between two semi-infinite media. Surface waves propagating along the material interface are sought. The physical problem is reduced to solving a nonlinear eigenvalue transmission problem for a system of two ordinary differential equations. A theorem on the existence and localization of at least one eigenvalue is proven. On the basis of this theorem, a method for finding approximate eigenvalues of the considered problem is proposed. Numerical results for Kerr and saturation nonlinearities are presented as examples.     

Interaction of modulated pulses in nonlinear oscillator chains

We formally derive and rigorously justify the modulation equations of lowest order for the interaction of two modulated pulses on a one-dimensional nonlinear oscillator chain. We show that solutions with the initial form of the assumed ansatz preserve this form over time intervals with positive macroscopic length, and we show a bound on the possible shift of the envelope caused by the interaction. Thus, we rigorously justify and quantify the statement that under the given conditions there is almost no interaction of the modulated pulses.     

Generation of plane shock waves in a specially shaped chamber

Movement of an ideal compressed liquid in a specially shaped chamber is considered. The possibility is demonstrated of obtaining with a point explosion shock waves with a front close to planar. The solution is performed by a break-up-discontinuity method.Translated from Teoreticheskaya i Prikladnaya Mekhanika, No. 18, pp. 127–129, 1987.     

Small-amplitude nonlinear waves on a black hole background

Let $G(x)$ be a $C^0$ function such that $|G(x)|⩽K{|x|}^p$ for $|x|⩽c$, for constants $K,c>0$. We consider spherically symmetric solutions of ${\square }_g\varphi =G(\varphi )$ where g is a Schwarzschild or more generally a Reissner–Nordström metric, and such that ϕ and ∇ϕ are compactly supported on a complete Cauchy surface. It is proven that for $p>4$, such solutions do not blow up in the domain of outer communications, provided the initial data are small. Moreover, $|\varphi |⩽C{(\max \{v,1\})}^{\mathrm{-1}}$, where v denotes an Eddington–Finkelstein advanced time coordinate.     

Formation of nonlinear magnetization oscillations by spin waves transmission through the boundary of two uniaxial ferromagnets

In this paper, the possibility of nonlinear spin wave formation at transmission of a bulk spin wave through the boundary of two ferromagnets with uniaxial magnetic anisotropy in the external magnetic field was shown at the certain conditions. The bulk spin waves with different values of precession angles of magnetizations can propagate in the second ferromagnet so both linear and nonlinear states can be excited. Also, expressions for coefficients of reflection and transmission of spin waves were obtained depending on value of a precession angle of magnetization in the second ferromagnet.