Euler-Lagrange equation from nonlocal-in-time kinetic energy of nonconservative system

This Letter focuses on studying generalized Euler-Lagrange equation and Hamiltonian framework from nonlocal-in-time kinetic energy of nonconservative system. According to Suykens' approach, we extend his results and formulate some work related to the nonconservative system. With the Lagrangian and nonconservative force in nonlocal-in-time form, we obtain the higher order generalized Euler-Lagrange equation which leads to an extension of Newton's second law of motion. The Hamiltonian is studied in relation to the Lagrangian in the canonical phase space. Finally, the particle with nonconservative force case is studied and compared with quantum mechanical results. The extended equation gives a possible approach for understanding the connection between classical and quantum mechanics.     

Universal fractional Euler-Lagrange equation from a generalized fractional derivate operator

The purpose of this paper is to extend the fractional actionlike variational approach by introducing a generalized fractional derivative operator. The generalized fractional formalism introduced through this work includes some interesting features concerning the fractional Euler-Lagrange and Hamilton equations. Additional attractive features are explored in some details.     

Non-uniqueness of gauge-field potentials

Two sets of phenomena peculiar to non-Abelian gauge theories are illustrated. The first concerns the existence of nonsingular potentials which generate the same field strength without being gauge-equivalent; a necessary condition for this ambiguity is obtained. The second exhibits the insufficiency of the cyclic identity in determining field strength-potential relations.     

Gerdjikov-Ivanov方程的精确解

研究在量子场理论、弱非线性色散水波、非线性光学等领域中出现的Gerdjikov-Ivanov方程.对Gerdjikov-Ivanov方程的研究会导出具有高次非线性项的非线性数学物理方程.选取Liénard方程作为辅助常微分方程,借助于它并根据齐次平衡原则,求解了Gerdjikov-Ivanov方程,得到了该方程的包络孤立波解和包络正弦波解. 关键词： 齐次平衡原则 F展开法 Gerdjikov-Ivanov方程 包络孤立波解     

Explicit solutions of Boussinesq--Burgers equation

Darboux transformation with multi-parameters for the Boussinesq--Burgers (B--B) equation is derived. For an application, some important explicit solutions of the B--B equation are obtained, including 2N-soliton solution and periodic solution. Finally, some elegant and interesting figures are plotted.     

Convection-diffusion-reaction equation with similarity solutions

We consider similarity solutions of the generalized convection-diffusion-reaction equation with both space- and time-dependent convection, diffusion and reaction terms. By introducing the similarity variable, the reaction-diffusion equation is reduced to an ordinary differential equation. Matching the resulting ordinary differential equation with known exactly solvable equations, one can obtain corresponding exactly solvable convection-diffusion-reaction systems. Some representative examples of exactly solvable systems are presented. We also describe how an equivalent convection-diffusion-reaction system can be constructed which admits the same similarity solution of another convection-diffusion-reaction system.     

Exact solutions for Ostrovsky equation

This paper obtains solutions to the Ostrovsky equation by employing the mapping method. Several solutions are determined including the cnoidal waves, shock waves, solitary waves, periodic singular waves and others in the case of no rotation. Finally, the ansatz method is applied to solve the equation with the rotation term present.     

Scaling solutions of Smoluchowski's coagulation equation

We investigate the structure of scaling solutions of Smoluchowski's coagulation equation, of the formc _k (t)s(t)^– (k/s(t)), wherec _k (t) is the concentration of clusters of sizek at timet,s(t) is the average cluster size, and(x) is a scaling function. For the rate constantK(i, j) in Smoluchowski's equation, we make the very general assumption thatK(i, j) is a homogeneous function of the cluster sizesi andj:K(i,j)=a ^– K(ai,aj) for alla>0, but we restrict ourselves to kernels satisfyingK(i, j)/j0 asj. We show that gelation occurs if>1, and does not occur if1. For all gelling and nongelling models, we calculate the time dependence ofs(t), and we derive an equation for(x). We present a detailed analysis of the behavior of(x) at large and small values ofx. For all models, we find exponential large-x behavior: (x)A x ^– e ^–x asx and, for different kernelsK(i, j), algebraic or exponential small-x behavior: (x)Bx ^– or (x)=exp(–Cx ^–|| + ...) asx0.     

Nonperturbative solutions of the Lane-Emden equation

A new, iterative approach to solving the Lane-Emden equation leads to approximate solutions which display the coupling constant as a persistent interaction. The approach generalizes to nonlinear field equations.     

Nonisotropic solutions of the Boltzmann equation

We consider the relaxation to equilibrium of a spatially uniform Maxwellian gas. We expand the solution of the nonlinear Boltzmann equation in a truncated series of orthogonal functions. We integrate numerically the equation for non-isotropic initial conditions. For certain simple conditions we find interesting proximity effects and other transient relaxation phenomena at thermal energies. Furthermore, we define a resummation of the orthogonal expansion which is more convenient than the original one for the numerical analysis of the relaxation process.     

Front-type solutions of fractional Allen-Cahn equation

Super-diffusive front dynamics have been analysed via a fractional analogue of the Allen-Cahn equation. One-dimensional kink shape and such characteristics as slope at origin and domain wall dynamics have been computed numerically and satisfactorily approximated by variational techniques for a set of anomaly exponents 1<γ<2. The dynamics of a two-dimensional curved front has been considered. Also, the time dependence of coarsening rates during the various evolution stages was analysed in one and two spatial dimensions.     

New solutions of the shape equation

The general shape equation describing the forms of vesicles is a highly nonlinear partial differential equation for which only a few explicit solutions are known. These solvable cases are briefly reviewed and a new analytical solution which represents the class of the constant mean curvature surfaces is described. Pearling states of the tubular fluid membranes can be explained as a continuous deformation preserving membrane mean curvature. Received 2 February 2002 / Received in final form 4 February 2002 Published online 2 October 2002 RID="a" ID="a"e-mail: mladenov@obzor.bio21.bas.bg     

Quasi-periodic solutions of the sine-Gordon equation

Two-phase quasi-periodic solutions of the sine-Gordon equation are discussed. It is shown that the solutions expressed by the multidimensional θ-function form a broader class than the well-known factorised solutions 4 arctan [f(u)g(v)]. Expressions describing the spatial and temporal period are also given.     

Mixed solutions of the sine-Gordon equation

The aim of this note is to present an explicit formula for the mixed solution of the sine-Gordon equation, i.e. the solution describing a multisoliton process on a background of multiphase quasi-periodic process.     

Symmetry-breaking solutions of the Ginzburg-Landau equation

We consider the question of the existence of nonradial solutions of the Ginzburg-Landau equation. We present results indicating that such solutions exist. We seek such solutions as saddle points of the renormalized Ginzburg-Landau free-energy functional. There are two main points in our analysis: searching for solutions that have certain point symmetries and characterizing saddle-point solutions in terms of critical points of certain intervortex energy function. The latter critical points correspond to forceless vortex configurations.     

Periodic solutions of the Ginzburg-Landau equation

Spatially periodic solutions to the Ginzburg-Landau equation are considered. In particular we obtain: criteria for primary and secondary bifurcation; limit cycle solutions; nonlinear dispersion relations relating spatial and temporal frequencies. Only relatively simple tools appear in the treatment and as a result a wide range of parameter cases are considered. Finally we briefly treat the case of spatial bifurcations.     

Steady solutions of the Kuramoto-Sivashinsky equation

Steady solutions of the Kuramoto-Sivashinsky equation are studied. These solutions are defined on the whole x line and propagate with a constant speed c² in time. For large c² it is shown that the solution is unique and has a conical form. For small c² there is a periodic solution and an infinite set of quasi-periodic solutions as asserted by Moser's twist map theorem. Numerical computations for intermediate values of c² suggest that below c ≈ 1.6 of every speed there is a continuum of odd quasi-periodic solutions or a Cantor set of chaotic solutions wrapped by infinite sequences of conic solutions.