On the uniform motion of a relativistic charged particle in a homogeneous electromagnetic field in Minkowski space

We discuss the geometric characterization of the trajectory of a moving charged particle, for the case of a homogeneous electromagnetic field, in Minkowski space when the motion is governed by the Lorentz equation. We employ a totally relativistic approach during the discussion. It is based on a systematic use of the Faraday antisymmetric tensor properties of the electromagnetic field and of the four‐dimensional Frenet‐Serret formula, which is adapted to the Minkowski 4‐space with index two to determine the worldline geometry of the electromagnetic field acting on the particle. Finally, we present the necessary and sufficient conditions to obtain uniform motion of the relativistic charged particle in a homogeneous electromagnetic field in      

Emission of Cherenkov radiation as a mechanism for Hamiltonian friction

We study the motion of a heavy tracer particle weakly coupled to a dense, weakly interacting Bose gas exhibiting Bose–Einstein condensation. In the so-called mean-field limit, the dynamics of this system approaches one determined by nonlinear Hamiltonian evolution equations. We prove that if the initial speed of the tracer particle is above the speed of sound in the Bose gas, and for a suitable class of initial states of the Bose gas, the particle decelerates due to emission of Cherenkov radiation of sound waves, and its motion approaches a uniform motion at the speed of sound, as time t tends to ∞.     

一个反应扩散方程解的熄灭行为

本文应用上下解方法和Ｌ^ｐ积分模估计的方法研究了一类反应扩散方程初边值问题正解的熄灭形为，给出解熄灭的参数环境．     

Obtaining equations of motion for charged particles in the (<Emphasis Type="Italic">v/c</Emphasis>)<Superscript>3</Superscript>-approximation by the Einstein-Infeld-Hoffmann method

We consider some principal methodological problems that appear when the Einstein-Infeld-Hoffmann method is used to find approximate solutions of the general relativity equations and to obtain information about the motion of particles whose interaction force is much greater than the gravitational attraction force. Among these problems are normalizing approximate expressions by expanding exact solutions written in the same coordinate conditions used in the Einstein-Infeld-Hoffmann method, assigning the smallness orders depending on relations between the smallness parameters in play, and verifying cancellations of divergent terms arising in surface integrals. Solving these questions in accordance with the internal logic of the Einstein-Infeld-Hoffmann method results in new tools and techniques for applying the method. We demonstrate these tools and techniques in the example of the problem of the motion of two electrically charged pointlike particles in the (v/c)³-approximation.Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 142, No. 1, pp. 160–176, January, 2005.     

A radiation condition for uniqueness in a wave propagation problem for 2‐D open waveguides

We study the uniqueness of solutions of Helmholtz equation for a problem that concerns wave propagation in waveguides. The classical radiation condition does not apply to our problem because the inhomogeneity of the index of refraction extends to infinity in one direction. Also, because of the presence of a waveguide, some waves propagate in one direction with different propagation constants and without decaying in amplitude. We provide an explicit condition for uniqueness for rectilinear waveguides, which takes into account the physically significant components, corresponding to guided and non‐guided waves; this condition reduces to the classical Sommerfeld–Rellich condition in the relevant cases. By a careful asymptotic analysis we prove that the solution derived by Magnanini and Santosa (SIAM J. Appl. Math. 2001; 61 :1237–1252) for stratified media satisfies our radiation condition. Copyright © 2008 John Wiley & Sons, Ltd.     

R2中非局部椭圆型方程基态解的存在性

本文考虑了一类非局部椭圆型方程-△u+V(x)u=(1/|x|μ*Q(x)F(u)/|x|β)Q(x)f(u)|x|β,x∈R^x,其中V是正的连续位势函数,0<μ<2,0≤β<1/2,2β+μ≤2,F(s)是f(s)的原函数.假设非线性项f(s)满足Trudinger-Moser型次临界指数增长,利用变分方法证明了该方程基态解的存在性.     

On a Strong Solution in the Method of Spherical Harmonics for a Nonstationary Transport Equation

We prove existence of a strong generalized solution in the Sobolev space W ₂ ¹ to the nonstationary problem for the system of the method of spherical harmonics (MSH) corresponding to the radiation transport problem.     

Preservation of Oscillations in the Runge-Kutta Method for a Type of Advanced Differential Equation

This article is concerned with the preservation of oscillations for differential equations with piecewise constant arguments of advanced type. By using the Runge-Kutta method, new oscillation conditions for numerical solution are established. We prove that oscillations of the analytic solution are preserved by the numerical solution in the Runge-Kutta method under some conditions. Some experiments are given.     

Integral Equation for the Spinor Amplitude of a Dirac Particle in a Curved Space–Time

We obtain a system of integral equations for the spinor amplitude of a wave packet describing a massive neutral Dirac particle in a curved space–time with an arbitrary geometry. This equation permits describing the spin dynamics of fermions in gravitational fields adequately to the quantum nature of spin. We consider a specific example of the Kerr–Schild metric. We also discuss the problem of massive neutrino oscillations in an external gravitational field.     

周期单元中相对论Boltzmann方程初值问题整体解的存在性

本文证明了周期单元中带有某些硬相互作用的相对论Ｂｏｌｔｚｍａｎｎ方程初值问题在初值满足质量、能量和熵有限的条件下具有一个整体温和解．     

A model and simulation for homeorhesis in the motion of a single individual

In contrast to nonliving systems, all living systems perform homeorhesis. The system state tends to the so-called necessary path, or creode, when the exogenous signals are in a certain system-relevant range. The present work develops the homeorhesis-aware dynamical model for the motion of a single individual (e.g., human). The model allows for the purposeful behaviour of the individual, the creode, the exogenous forces, and the individual-specific sensitivity to their influences. The model also describes the homeorhetic-dysfunction movements. The transparency of the model is such that it allows a physical analogue in the form of electronic circuits. The model is a first step towards the construction of sociologically relevant models for the prediction of human behaviour. It is indispensable for the analyses of dangerous scenarios where the experiments are impossible, for example when predicting the behaviour of panic-stricken crowds in life-threatening situations. The work illustrates the corresponding numerical-simulation results with a series of figures and suggests topics for future research.     

一个抛物型方程侧边值问题的正则逼近解在一类Sobolev空间中的最优误差界

逆热传导问题(IHCP)是严重不适定问题,即问题的解(如果存在)不连续依赖于数据．但目前关于逆热传导问题的已有结果主要是针对标准逆热传导问题．文中给出了出现在实际问题中的一个抛物型方程侧边值问题,即一个含有对流项的非标准型逆热传导问题的正则逼近解一类Sobolev空间中的最优误差界．     

Blow up for Initial-Boundary Value Problem of Wave Equation with a Nonlinear Memory in 1-D

The present paper is devoted to studying the initial-boundary value problem of a 1-D wave equation with a nonlinear memory: u_(tt) - u_(xx) = 1/ Γ(1 - γ) ∫_0~t (t - s)~(-γ)|u(s)|~pds. The blow up result will be established when p 1 and 0 γ 1, no matter how small the initial data are, by introducing two test functions and a new functional.     

抽象空间中一类带奇异性的混合型积分-微分方程边值问题的正解

利用不动点指数理论,研究了Banach空间中一类带奇性的混合型积分——微分方程边值问题正解的存在性,得到了多个正解存在的充分条件,并给出了相应的例子以说明所得结果的合理性和应用性.     

Existence and Multiplicity of Solutions for a Biharmonic Kirchhoff Equation in $\mathbb{R}^5$

We consider the biharmonic equation $\Delta^2u-\left(a+b\int_{\R^5}|\nabla u|^2dx\right)\Delta u\\+V(x)u=f(u)$, where $V(x)$ and $f(u)$ are continuous functions. By using a perturbation approach and the symmetric mountain pass theorem, the existence and multiplicity of solutions for this equation are obtained, and the power-type case $f(u)=|u|^{p-2}u$ is extended to $p\in(2,10)$, where it was assumed $p\in(4,10)$ in many papers.     

具有转向点超曲面的奇摄动椭圆型方程边值问题

本文利用多重尺度法和比较定理，研究了n维空间中一类具有转向点超曲面的奇摄动椭圆方程边值问题，研究了该值问题解的渐近性态。     

在部分区域上的奇摄动反应扩散方程初始边值问题解的渐近性态

讨论一类在部分区域上的奇摄动反应扩散方程初始边值问题,利用算子理论,得到了相应问题解的渐近性态。     

Existence and Nonexistence of Traveling Wave Solutions for a Bistable Reaction-Diffusion Equation in an Infinite Cylinder Whose Diameter is Suddenly Increased

ABSTRACT

We consider a reaction-diffusion equation of bistable type in a square cylinder whose diameter varies with Neumann boundary conditions in dimension 2 and 3. We prove the nonexistence of generalized traveling wave solution of this equation when the diameter is suddenly strongly increased. At the same time, we prove that the solution of the equation with an exponentially decreasing initial condition cannot pass over a certain threshold far enough in the direction of propagation.

The proof is divided in two steps. First, we extend the solution in the cylinder to a solution of the same equation in the half space. Then we overestimate it using Green's functions.