Almost Periodic Solutions of Equation $[\dot x = {x^3} + \lambda g(t)x + \mu f(t)\]$ and Their Stability

By using the Liapunov function and the contraction mapping principle, the author investigates the existence and stability of almost periodic solutions of the first order nonlinear equations $\frac{dx}{dt}=-h_1(x)+h_2(x)g(t)+f(t)$ and $\frac{dx}{dt}=r(t)x^n+\lambdag(t)x+\muf(t)$, where r(t), g(t), f(t) are given almost periodic functions, n(\geq 2) integer, and \lambda,\mu real parameters.     

On the functional equationf(x) g(y) = p(x + y) q(x/y)

Aequationes mathematicae -     

On the functional equation $$G\left( x,G\left( y,x\right) \right) = G\left( y,G\left( x,y\right) \right) $$Gx,Gy,x=Gy,Gx,y and means

Periodica Mathematica Hungarica - We consider the functional equation $$G\left( x,G\left( y,x\right) \right) =G\left( y,G\left( x,y\right) \right) $$, posed in Jarczyk and Jarczyk (Aequ Math...     

On controllability of systems of the form\dot x=A(t)x+g(t,u)

In an earlier paper, the author established a sufficient condition for controllability of systems of the form =A(t)x+g(t, u). This condition is a growth condition which generalizes the concept of an asymptotically proper system introduced by LaSalle for linear systems. The purpose of this paper is examine and apply this growth condition. We first show that the condition is also necessary for controllability. Then, we use these results to consider the controllability of perturbations of the above system. The main result of the paper is a class of systems which in many applications can be assumed to be controllable.During the writing of this paper, the author held a Junior Faculty Summer Fellowship from the Research Council of the University of Nebraska.     

On the Equations zm = F(x, y) and Axp + Byq = Czr

We investigate integer solutions of the superelliptic equation where F is a homogeneous polynomialwith integer coefficients, and of the generalized Fermat equation where A, B and C are non-zero integers.Call an integer solution (x, y, z) to such an equation properif gcd(x, y, z) = 1. Using Faltings' Theorem, we shall givecriteria for these equations to have only finitely many propersolutions. We examine (1) using a descent technique of Kummer, which allowsus to obtain, from any infinite set of proper solutions to (1),infinitely many rational points on a curve of (usually) highgenus, thus contradicting Faltings' Theorem (for example, thisworks if F(t, 1) = 0 has three simple roots and m 4). We study (2) via a descent method which uses unramified coveringsof P₁ \ {0, 1, } of signature (p, q, r), and show that (2) hasonly finitely many proper solutions if l/p + l/q + 1/r <1. In cases where these coverings arise from modular curves,our descent leads naturally to the approach of Hellegouarchand Frey to Fermat's Last Theorem. We explain how their ideamay be exploited for other examples of (2). We then collect together a variety of results for (2) when 1/p+ 1/q + 1/r 1. In particular, we consider ‘local-global’principles for proper solutions, and consider solutions in functionfields.     

On the boundedness of the solutions of the equation\dddot x + a\ddot x + f(x)\dot x + g(x) = p(t)

Summary In this paper my previous result [1] on the boundedness of solutions of (1.1.1) is fackled by use of a suitably chosen Liapounov function. This fresh approach leads to a more direct proof of the boundedness Theorem and makes for substantial reduction in each of my previous conditions on f and g.     

On the existence of periodic solutions for the equation\ddot x + f(x)\dot x + g(x) = 0

We establish in this work sufficient conditions for the existence of periodic solutions for the Liénard equation .     

迭代函数方程$G(x,f(x),\ldots,f^n(x))=F(x)$的$C^1$解

In this paper we consider the iterative equation G(x,f(x),...,f n(x)) = F(x) on R,and give the existence of C 1 solutions near the fixed point of F,which generalize some results on the leading coefficient problem from the form of the polynomial-like iterative equations to the general form.     

Existence of exactlyn+1 simple 4-periodic solutions of the differential delay equation\dot x(t) = - f(x(t - 1))

By discussing the zeros of periodic solutions we give in this paper a criterion for the existence of exactlyn+1 simple 4-periodic solutions of the differential delay equation Supported by the Chinese National Foundation for Natural Sciences.     

Periodic solutions of the differential delay equation\dot x(t) = - f(x(t - 1))

For an odd function 1/2(x) defined only on a finite interval, this paper deals with the existence of periodic solutions and the number of simple periodic solutions of the differential delay equation (DDE) . By use of the method of qualitative analysis combined with the constructing of special solutions a series of interesting results are obtained on these problems.Supported by the National Natural Science Foundation of China.     

Asymptotic behavior of multiperiodic functionsG(x) = \prod\limits_{n = 1}^\infty {g(x/2^n )}

Let 0≤g be a dyadic Hölder continuous function with period 1 and g(0)=1, and let $G(x) = \prod\nolimits_{n = 0}^\infty {g(x/{\text{2}}^n )} $ . In this article we investigate the asymptotic behavior of $\smallint _0^{\rm T} \left| {G(x)} \right|^q dx$ and $\frac{1}{n}\sum\nolimits_{k = 0}^n {\log g(2^k x)} $ using the dynamical system techniques: the pressure function and the variational principle. An algorithm to calculate the pressure is presented. The results are applied to study the regulatiry of wavelets and Bernoulli convolutions.     

Integral Representation of Analytical Solutions of the Equation $$yf'_x - xf'_y = g(x,y) $$

Mathematical Notes -     

Exact formulae for periodic solutions of\dot x(t + 1) = \alpha x(t) + bx^3 (t))

An explicit formula for the symmetric period-4-solutions of the odd cubic differential delay equation is calculated together with a formula for its primary branch. The qualitative behavior of the primary branch is discussed.

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Zusammenfassung Die symmetrischen Periode-4-Lösungen der ungeraden kubischen verzögerten Differentialgleichung werden zusammen mit einer Formel für ihren Primärzweig exakt berechnet. Das qualitative Verhalten des Primärzweiges wird diskutiert.

     

Existence and Extendability of Solutions of the Equation g(t,x) = 0

We consider the problem of extendability and existence of solutions of the equation g(t, x) = 0 on the maximum interval of their definition.