On the Hamilton-Jacobi equation in the framework of generalized functions

In this work we study, in the framework of Colombeau?s generalized functions, the Hamilton-Jacobi equation with a given initial condition. We have obtained theorems on existence of solutions and in some cases uniqueness. Our technique is adapted from the classical method of characteristics with a wide use of generalized functions. We were led also to obtain some general results on invertibility and also on ordinary differential equations of such generalized functions.     

Singular generalized functions of an infinite-dimensional argument

It is proved that every generalized function (on a Hilbert space), concentrated on a surface of infinite codimension, is equal to zero.Translated from Matematicheskie Zametki, Vol. 22, No. 4, pp. 543–551, October, 1977.     

Analog of the cauchy function for a generalized equation with several deviations of the argument

We define a special multiplication of function series (skew multiplication) and a generalized Riemann-Stieltjes integral with function series as integration arguments. The generalized integrals and the skew multiplication are related by an integration by parts formula. The generalized integrals generate a family of linear generalized integral equations, which includes a family (represented in integral form via the Riemann-Stieltjes integral) of linear differential equations with several deviating arguments. A specific feature of these equations is that all deviating functions are defined on the same closed interval and map it into itself. This permits one to avoid specifying the initial functions and imposing any additional constraints on the deviating functions. We present a procedure for constructing the fundamental solution of a generalized integral equation. With respect to the skew multiplication, it is invertible and generates the product of the fundamental solution (a function of one variable) by its inverse function (a function of the second variable). Under certain conditions on the parameters of the equation, the product has all specific properties of the Cauchy function. We introduce the notion of adjoint generalized integral equation, obtain a representation of solutions of the original equation and the adjoint equation in generalized integral Cauchy form, and derive sufficient conditions for the convergence of solutions of a pair of adjoint equations.     

On the stability of some functional equations for generalized hyperbolic functions and for the generalized cosine equation

Two stability results concerning a system of functional equations for generalized hyperbolic and trigonometric functions on the one hand, and a generalized cosine equation on the other hand are presented.     

On the generalized Burgers equation

The present paper is concerned with the initial boundary value problem for the generalized Burgers equation u _t + g(t, u)u _x + f(t, u) = εu _xx which arises in many applications. We formulate a condition guaranteeing the a priori estimate of max |u _x | independent of ε and t and give an example demonstrating the optimality of this condition. Based on this estimate we prove the global existence of a unique classical solution of the problem and investigate the behavior of this solution for ε → 0 and t → + ∞. The Cauchy problem for this equation is considered as well.     

On the generalized associativity equation

The so-called generalized associativity functional equation

$$\begin{aligned} G(J(x,y),z) = H(x,K(y,z)) \end{aligned}$$

has been investigated under various assumptions, for instance when the unknown functions G, H, J, and K are real, continuous, and strictly monotonic in each variable. In this note we investigate the following related problem: given the functions J and K, find every function F that can be written in the form

$$\begin{aligned} F(x,y,z) = G(J(x,y),z) = H(x,K(y,z)) \end{aligned}$$

for some functions G and H. We show how this problem can be solved when any of the inner functions J and K has the same range as one of its sections.

     

On analytic functions related with generalized Robertson functions

Analytic functions f are called Robertson functions for which zf^′ is α-spiral-like. This concept is generalized by several authors and a class real, of analytic functions is introduced and studied. It is noted that the functions in are of bounded boundary rotation and consists of Robertson functions.In this paper, we use the class to define a new class of analytic functions which unifies a number of classes previously studied such as the class of close-to-convex functions of higher order. Some interesting properties of this class, including coefficient problems, inclusion results and a sufficient condition for univalency are studied.     

On solutions of a neutral differential equation with deviating argument

We prove a theorem on the existence and asymptotic behaviour of solutions of a differential equation with a deviating argument of neutral type. The considered equation contains both delayed and advanced arguments. The method used in the proof of our main result depends on conjunction of the classical Schauder fixed point theorem with the technique of measures of noncompactness.     

Solution of generalized bisymmetry type equations without surjectivity assumptions

Summary. The solution of the rectangular m ×n m \times n generalized bisymmetry equation¶¶F(G₁(x₁₁,...,x_1n),..., G_m(x_m1,...,x_mn))     =     G(F₁(x₁₁,..., x_m1),...,  F_n(x_1n,...,x_mn) ) F\bigl(G_1(x_{11},\dots,x_{1n}),\dots,\ G_m(x_{m1},\dots,x_{mn})\bigr) \quad = \quad G\bigl(F_1(x_{11},\dots, x_{m1}),\dots, \ F_n(x_{1n},\dots,x_{mn}) \bigr) (A)¶is presented assuming that the functions F, G_j, G and F_i (j = 1, ... , m , i = 1, ... , n , m S 2, n S 2) are real valued and defined on the Cartesian product of real intervals, and they are continuous and strictly monotonic in each real variable. Equation (A) is reduced to some special bisymmetry type equations by using induction methods. No surjectivity assumptions are made.     

The generalized cauchy equation for operator-valued functions

Aequationes mathematicae -     

On the generalized Korteweg-de Vries equation

We prove that the local L² norm of the solution of the generalized Korteweg-de Vries equation $$u_t + (F(u) + \sum\limits_{s = 0}^m {( - 1)^s D_x^{2s} u)_x = 0,m \geqslant 2,} $$ with nice initial datum, where F satisfies certain general conditions, for example, P(u) = u^p, where p is an odd integer ≧3, decays t o zero as time goes to infinity.     

Stability for quadratic functional equation in the spaces of generalized functions

In this paper, we consider the general solution of quadratic functional equation

f(ax+y)+f(ax−y)=f(x+y)+f(x−y)+2(a²−1)f(x)