arXiv subjects

Olena Atlasiuk

Publications and source records attributed to Olena Atlasiuk.

12 recordsLinked to original sources

arXiv2026

Limit theorems for differential systems with multipoint boundary conditions in Sobolev spaces

The most general class of multipoint inhomogeneous boundary-value problems for systems of linear ordinary differential equations of arbitrary order $r\geq 1$ is investigated, whose solutions belong to a given Sobolev space $W_p^{n+r}$, where $n\geq 0$ and $1\leq p\leq \infty$. The boundary conditions in these problems contain Caputo derivatives of fractional or integer orders, which may exceed the order of the differential system equations. Constructive sufficient conditions are established under which the solutions of these problems are continuous with respect to a parameter from an abstract metric space in the Sobolev space $W_p^{n+r}$.

math.CA↗

arXiv2026

On parameter-dependent inhomogeneous boundary-value problems in Sobolev spaces

We study a wide class of linear inhomogeneous boundary-value problems for $r$th order ODE-systems depending on a parameter $μ$ belonging to a general metric space $\mathcal M$. The solutions belong to the Sobolev spaces $(W^{n+r}_p)^m$, $n\in\mathbb{N}\cup\{0\}$, $m, r \in \mathbb{N}$, $1\leq p\leq \infty$. The boundary conditions are of a most general form $By=c$, where $B$ is an arbitrary continuous operator from $(W^{n+r}_p)^m$ to $\mathbb{C}^{rm}$. Thus, they may contain derivatives of the unknown vector function of integer and/or fractional orders $\geq r$. We find necessary and sufficient conditions for the continuity of solutions with respect to the parameter $μ$. We also prove that the solutions of the original problems can be approximated in the space $(W^{n+r}_p)^m$ by solutions of ODE-systems with polynomial coefficients, right-hand sides of the equation, and multipoint boundary conditions, which are independent of the original problem's right-hand sides.

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arXiv2025

Parameter-dependent inhomogeneous boundary-value problems in Sobolev spaces

We study a wide class of linear inhomogeneous boundary-value problems for $r$th order ODE-systems depending on a parameter $μ$ in a general metric space $\mathcal M$. The solutions belong to the Sobolev spaces $(W^{n+r}_p)^m$, $n\in\mathbb{N}\cup\{0\}$, $m, r \in \mathbb{N}$, $1\leq p\leq \infty$. The boundary conditions are of a most general form $By=c$, where $B$ is an arbitrary continuous operator from $(W^{n+r}_p)^m$ to $\mathbb{C}^{rm}$. They may thus contain derivatives of the unknown vector function of integer and/or fractional orders $\geq r$. We find necessary and sufficient conditions for the continuity of solutions with respect to the parameter $μ$. We also prove that the solutions of the original problems can be approximated in the space $(W^{n+r}_p)^m$ by solutions of ODE-systems with polynomial coefficients and multipoint boundary conditions, which do not depend on the right-hand sides of the original problem.

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arXiv2025

Continuity in a parameter of solutions to boundary-value problems in Sobolev spaces

We consider the most general class of linear inhomogeneous boundary-value problems for systems of ordinary differential equations of an arbitrary order whose solutions and right-hand sides belong to appropriate Sobolev spaces. For parameter-dependent problems from this class, we prove a constructive criterion for their solutions to be continuous in the Sobolev space with respect to the parameter. We also prove a two-sided estimate for the degree of convergence of these solutions to the solution of the nonperturbed problem.

math.CA↗

arXiv2024

Differential systems in Sobolev spaces with generic inhomogeneous boundary conditions

The paper contains a review of results on linear systems of ordinary differential equations of an arbitrary order on a finite interval with the most general inhomogeneous boundary conditions in Sobolev spaces. The character of the solvability of such problems is investigated, their Fredholm properties are established, and their indexes and the dimensions of their kernels and co-kernels are found. In addition, necessary and sufficient conditions of continuity in the parameter of the solutions of the introduced classes of boundary-value problems in Sobolev spaces of an arbitrary order are obtained.

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arXiv2024

Weak solutions for a singular beam equation

This paper deals with a dynamic Gao beam of infinite length subjected to a moving concentrated Dirac mass. Under appropriate regularity assumptions on the initial data, the problem possesses a weak solution which is obtained as the limit of a sequence of solutions of regularized problems.

math.AP↗

arXiv2023

On Differential Systems in Sobolev spaces with Generic Inhomogeneous Boundary Conditions

We study linear systems of ordinary differential equations of an arbitrary order on a finite interval with the most general (generic) inhomogeneous boundary conditions in Sobolev spaces. We investigate the character of solvability of inhomogeneous boundary-value problems, prove their Fredholm properties, and find the indices, the dimensions of the kernel, and the cokernel of these problems. Moreover, we obtained necessary and sufficient conditions for continuity in a parameter of solutions to the introduced problems in Sobolev spaces.

math.CA↗

arXiv2023

The solvability of inhomogeneous boundary-value problems in Sobolev spaces

The aim of the paper is to develop a general theory of solvability of linear inhomogeneous boundary-value problems for systems of ordinary differential equations of arbitrary order in Sobolev spaces. Boundary conditions are allowed to be overdetermined or underdetermined. They may contain derivatives, of the unknown vector-valued function, whose integer or fractional orders exceed the order of the differential equation. Similar problems arise naturally in various applications. The theory introduces the notion of a rectangular number characteristic matrix of the problem. The index and Fredholm numbers of this matrix coincide respectively with the index and Fredholm numbers of the inhomogeneous boundary-value problem. Unlike the index, the Fredholm numbers (i.e. the dimensions of the problem kernel and co-kernel) are unstable even with respect to small (in the norm) finite-dimensional perturbations. We give examples in which the characteristic matrix can be explicitly found. We also prove a limit theorem for a sequence of characteristic matrices. Specifically, it follows from this theorem that the Fredholm numbers of the problems under investigation are semicontinuous in the strong operator topology. Such a property ceases to be valid in the general case.

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arXiv2023

On the solvability of Fredholm boundary-value problems in fractional Sobolev spaces

Systems of linear ordinary differential equations with the most general inhomogeneous boundary conditions in fractional Sobolev spaces on a finite interval are studied. The Fredholm property of such problems in corresponding pairs of Banach spaces is proved, and their indices and dimensions of kernels and cokernels are found. Examples are given that show the constructive character of the obtained results.

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arXiv2019

On Linear Boundary-Value Problems for Differential Systems in Sobolev spaces

We consider the Fredholm one-dimensional boundary-value problems in Sobolev spaces.We have obtained several important results about the indixes of functional operators, the criterion of their correct well-posedness, the criterion of the continuous dependence of the solutions of these problems on the parameter, the degree of convergence of these solutions, and sufficient constructive conditions under which the solutions of the most general class of multipoint boundary-value problems are continuous with respect to the parameter. Eeach of these boundary-value problems corresponds to a certain rectangular numerical characteristic matrix with kernel and cokernel of the same dimension as the kernel and cokernel of the boundary-value problem. The conditions for the sequence of characteristic matrices to converge are found.

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arXiv2019

Fredholm one-dimensional boundary-value problems with parameter in Sobolev spaces

For systems of linear differential equations on a compact interval, we investigate the~dependence on a parameter $\varepsilon$ of the solutions to boundary-value problems in the Sobolev spaces $W^{n}_{\infty}$. We obtain a constructive criterion of the continuous dependence of the solutions of these problems on the~parameter $\varepsilon$ for $\varepsilon=0$. The degree of convergence of these solutions is established.

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arXiv2019

Fredholm one-dimensional boundary-value problems in Sobolev spaces

For systems of ordinary differential equations on a compact interval, we study the character of solvability of the most general linear boundary-value problems in Sobolev spaces. We find the indices of these problems and obtain a criterion of their well-posedness.

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