Approximation properties of solutions to multipoint boundary-value problems

UDC 517.927 We consider a wide class of linear boundary-value problems for systems of $m$ ordinary differential equations of order $r$ known as the general boundary-value problems. Their solutions $y\colon[a,b]\to \mathbb{C}^{m}$ belong to the Sobolev space $(W_1^{r})^m,$ and the boundary conditions...

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Date:2021
Main Authors: Murach, A. A., Pelekhata, O. B., Soldatov, V. O., Мурач, А. А., Пелехатая, О. Б., Солдатов, В. О., Мурач, О. О., Пелехата, О. Б.
Format: Article
Language:Ukrainian
Published: Institute of Mathematics, NAS of Ukraine 2021
Online Access:https://umj.imath.kiev.ua/index.php/umj/article/view/6505
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Journal Title:Ukrains’kyi Matematychnyi Zhurnal
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Ukrains’kyi Matematychnyi Zhurnal
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Summary:UDC 517.927 We consider a wide class of linear boundary-value problems for systems of $m$ ordinary differential equations of order $r$ known as the general boundary-value problems. Their solutions $y\colon[a,b]\to \mathbb{C}^{m}$ belong to the Sobolev space $(W_1^{r})^m,$ and the boundary conditions are given in the form $By=q$ where $B\colon(C^{(r-1)})^{m}\to\mathbb{C}^{rm}$ is an arbitrary continuous linear operator. For such a problem, we prove that its solution can be approximated in $(W_1^{r})^m$ with arbitrary precision by solutions to multipoint boundary-value problems with the same right-hand sides. These multipoint problems are built explicitly and do not depend on the right-hand sides of the general boundary-value problem. For these problems, we obtain estimates of error of solutions in the normed spaces $(W_1^{r})^m$ and $(C^{(r-1)})^{m}.$  
DOI:10.37863/umzh.v73i3.6505