Linear second-order differential equations with degenerating coefficient of the second derivative

For an ordinary linear second-order differential equation with degenerating coefficient of the higher derivative, we obtain exact asymptotic representations of solutions near the degeneration point, which are convergent uniformly and absolutely in some neighborhood of that point. The results permit one to obtain well-posed statements of initial and boundary value problems for degenerating equations and establish oscillation properties of solutions.     

Computation of the asymptotics of solutions for equations with polynomial degeneration of the coefficients

We study linear differential equations with holomorphic coefficients. We establish the reducibility of such equations to equations with degeneration in the principal symbol. For the case of cuspidal degeneration, we show that the solutions of such equations are resurgent whenever so are their right-hand sides. We also refine earlier-obtained asymptotics of solutions for some equations of this type.     

Transmutations and irregular singular points

We consider transumtations for a class of problems in partial differential equations where the underlying equation, involving two assignable parameters, is an associated ordinary differential equation with an irregular singular point. An integral formula for the solution of this associated problem, valid for negative values of a timelike variable t, permits relating the solution of the problems in partial differential equations to be bounded or slow groth solutions of generalized heat problems. Applications of the formulas are made to Cauchy and boundary type problems.     

Steady-state oscillations in continuously inhomogeneous medium described by the generalized darboux equation

We refine a result due to L. V. Ovsyannikov on the general formof the second order linear differential equations with a nonzero generalized Laplace which are invariant admitting a Lie group of transformations of the maximal order with n > 2 independent variables for which the associated Riemannian spaces have nonzero curvature. We show that the set of these equations is exhausted by the generalized Darboux equation and the Ovsyannikov equation. We find the operators acting on the set of solutions in every one-parameter family of generalized Darboux equations. For the elliptic generalized Darboux equation possessing the maximal symmetry and describing steadystate oscillations in continuously inhomogeneous medium with a degeneration hyperplane, the group analysis methods yield the exact solutions to boundary value problems for some regions (a generalized Poisson formula) which in particular can be the test solutions in simulating steadystate oscillations in continuously inhomogeneous media.     

Invariant imbedding and Riccati transformations

From its inception, the theory of invariant imbedding has been concerned with the study of various relations between the inputs and outputs of various physical processes. Where the processes could be modelled by differential or integro-differential equations, these ideas have led to the heuristic development of various functional relationships for the solutions of these equations. In this work, we show that for a general class of two point boundary value problems these relations can be obtained from mathematical arguments rather than physical ones. The principal result is the establishment of the equivalence of solving a family of two point boundary value problems and that of determining the existence of two transformations on the set of solutions of the given differential equations. We refer to these transformations as Riccati transformations. They are shown to be determined by a set of initial value problems which generalize the invariant imbedding equations obtained by previous authors. We work in the coordinate free setting of a Banach space. The usefulness of this approach is shown as we are able to readily extend our results to nonlocal and multipoint boundary conditions. An indication is made of how a similar theory applies to a class of problems for difference equations.     

Introduction to the theory of functional differential equations and their applications. Group approach

In this work, we give an introduction to the theory of nonlinear functional differential equations of pointwise type on a finite interval, semi-axis, or axis. This approach is based on the formalism using group peculiarities of such differential equations. For the main boundary-value problem and the Euler-Lagrange boundary-value problem, we consider the existence and uniqueness of the solution, the continuous dependence of the solution on boundary-value and initial-value conditions, and the “roughness” of functional differential equations in the considered boundary-value problems. For functional differential equations of pointwise type we also investigate the pointwise completeness of the space of solutions for given boundary-value conditions, give an estimate of the rank for the space of solutions, describe types of degeneration for the space of solutions, and establish conditions for the “smoothness” of the solution. We propose the method of regular extension of the class of ordinary differential equations in the class of functional differential equations of pointwise type. __________ Translated from Sovremennaya Matematika. Fundamental’nye Napravleniya (Contemporary Mathematics. Fundamental Directions), Vol. 8, Functional Differential Equations, 2004.     

二阶奇异超线性微分方程正解的存在性和不可比较性

本文通过构造—个特殊的锥,利用范数形式的锥拉伸不动点定理对较广泛的一类二阶奇异超线性微分方程边值问题做了研究,得到所述问题的Cp1[0,1]正解存在的充分条件、必要条件,以及Cp1[0,1]正解的不可比较性．     

Banach空间二阶非线性微分方程的弱Carathéodory解

本文定义了二阶微分方程的弱 Carathéodory解 ,在不涉及紧型条件的情形下 ,直接用迭代法证明了 Banach空间二阶非线性常微分方程两点边值问题存在唯一解 ,并给出逼近解迭代序列的误差估计 ,对周期边值问题得到类似的结果     

一类微分方程组的非齐次Sturm-Liouville边值问题解的存在性

在允许非线性项变号的情况下,利用锥上不动点定理,讨论了一类二阶非线性微分方程组的非齐次Sturm-Liouville边值问题解的存在性,得到了至少一个解及正解存在的多个存在性定理．     

Positive solutions for fourth-order differential equations with deviating arguments and integral boundary conditions

In this paper we investigate integral boundary value problems for fourth order differential equations with deviating arguments. We discuss our problem both for advanced or delayed arguments. We establish sufficient conditions under which such problems have positive solutions. To obtain the existence of multiple (at least three) positive solutions, we use a fixed point theorem due to Avery and Peterson. An example is also included to illustrate that corresponding assumptions are satisfied. The results are new.     

泛函积分方程的正解与应用

运用锥拉伸与压缩不动点定理,研究一类泛函积分方程的正解．把所得结果应用于研究常微分方程积分边值问题正解的存在性,所得结果推广和本质上改进了马如云等作者最近的一些结果．     

具有分数导数的p-Laplace方程非局部边值问题的多个正解

In this paper,we study the multiple positive solutions of integral boundary value problems for a class of p-Laplacian differential equations involving the Caputo fractional derivative.Using a fixed point theorem due to Avery and Peterson,we obtain the existence of at least three positive decreasing solutions of the nonlocal boundary value problems. We give an example to illustrate our results.     

Differential equations with degeneration and resurgent analysis

In the present paper, we consider differential equations with cusp-type degeneration in the principal symbol. We prove the existence of an endlessly continuable solution in the case of Fredholm equations with endlessly continuable right-hand side. For the case in which the principal symbol of the operator has simple singularities, we obtain asymptotic expansions of the solutions of equations with degeneration.     

Multiple Positive Solutions of Nonlocal Boundary Value Problems for p-Laplacian Equations with Fractional Derivative

In this paper,we study the multiple positive solutions of integral boundary value problems for a class of p-Laplacian differential equations involving the Caputo fractional derivative.Using a fixed point theorem due to Avery and Peterson,we obtain the existence of at least three positive decreasing solutions of the nonlocal boundary value problems. We give an example to illustrate our results.     

Local and global existence of mild solution to an impulsive fractional functional integro-differential equation with nonlocal condition

This paper is concerned with the local and global existence of mild solution for an impulsive fractional functional integro differential equations with nonlocal condition. We establish a general framework to find the mild solutions for impulsive fractional integro-differential equations, which will provide an effective way to deal with such problems. The results are obtained by using the fixed point technique and solution operator on a complex Banach space.     

Impulsive boundary value problems with nonlinear boundary conditions

In this paper, the upper and lower solution method and Schauder’s fixed point theorem are employed in the study of boundary value problems for a class of second-order impulsive ordinary differential equations with nonlinear boundary conditions. We prove the existence of solutions to the problem under the assumption that there exist lower and upper solutions associated with the problem.     

Positive Solutions of One-Dimensional <Emphasis Type="Italic">p</Emphasis>-Laplacian Boundary Value Problems for Fourth-Order Differential Equations with Deviating Arguments

This paper considers the existence of positive solutions of four-point boundary value problems for fourth-order ordinary differential equations with deviating arguments and p-Laplacian. We discuss such problems in the cases when the deviating arguments are delayed or advanced, what may concern optimization issues related to some technical problems. To obtain the existence results, a fixed point theorem for cones due to Avery and Peterson is applied. According to the Author’s knowledge, the results are new. It is a first paper where a fixed point theorem for cones is applied to fourth-order differential equations with deviating arguments and p-Laplacian. An example is included to verify the theoretical results.     

Identifying unknown terms in hyperbolic and parabolic equations

We recover unknown source terms in nonlinear hyperbolic differential equations and in nonlinear parabolic integro-differential equations in one space variable under the assumption of knowing a first integral (in the hyperbolic case) or the value of the solution at a point inside the domain (in the parabolic case). For this class of problems we prove existence results in classes of smooth solutions. Moreover, for linear hyperbolic and parabolic differential equations in one space variable we recover some characteristic parameters. Conferenza tenuta il giorno 29 Novembre 1999     

Investigation of positive solution to a coupled system of impulsive boundary value problems for nonlinear fractional order differential equations

In this article, we study a coupled system of impulsive boundary value problems for nonlinear fractional order differential equations. We obtain sufficient conditions for existence and uniqueness of positive solutions. We use the classical fixed point theorems such as Banach fixed point theorem and Krasnoselskii’s fixed point theorem for uniqueness and existence results. As in application, we provide an example to illustrate our main results.     

Asymptotics of solutions of inhomogeneous equations with higher-order degeneration

We study inhomogeneous differential equations with higher-order degeneration in the coefficients in the resonance-free case and construct the asymptotics of their solutions.