This article considers continuous functions defined on the boundary of a bounded domain $D$ in $mathbb C^n$, $n>1$, and having a generalized boundary Morera property. The question of the existence of a holomorphic continuation of such functions into the domain $D$ for some sufficient sets $Gamma$ of complex lines intersecting the germ of the generating manifold lying inside the domain is investigated.
{"title":"On some sets sufficient for holomorphic continuation of functions with generalized boundary Morera property","authors":"A.M. Kytmanov, S.G. Myslivets","doi":"10.35634/vm230307","DOIUrl":"https://doi.org/10.35634/vm230307","url":null,"abstract":"This article considers continuous functions defined on the boundary of a bounded domain $D$ in $mathbb C^n$, $n>1$, and having a generalized boundary Morera property. The question of the existence of a holomorphic continuation of such functions into the domain $D$ for some sufficient sets $Gamma$ of complex lines intersecting the germ of the generating manifold lying inside the domain is investigated.","PeriodicalId":43239,"journal":{"name":"Vestnik Udmurtskogo Universiteta-Matematika Mekhanika Kompyuternye Nauki","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135686325","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We consider the arrangement of vertices of a unit multidimensional cube, an affine subspace, and its orthogonal projections onto coordinate subspaces. Upper and lower bounds on the subspace dimension are given under which some orthogonal projection always preserves the incidence relation between the subspace and cube vertices. Some oblique projections are also considered. Moreover, a brief review of the history of the development of multidimensional descriptive geometry is given. Analytic and synthetic methods in geometry diverged since the 17th century. Although both synthesis and analysis are tangled, from this time forth many geometers as well as engineers keep up a nice distinction. One can find references to the idea of higher-dimensional spaces in the 18th-century works, but proper development has been since the middle of the 19th century. Soon such works have appeared in Russian. Next, mathematicians generalized their theories to many dimensions. Our new results are obtained by both analytic and synthetic methods. They illustrate the complexity of pseudo-Boolean programming problems because reducing the problem dimension by orthogonal projection meets obstacles in the worst case.
{"title":"On a cube and subspace projections","authors":"A.A. Boykov, A.V. Seliverstov","doi":"10.35634/vm230302","DOIUrl":"https://doi.org/10.35634/vm230302","url":null,"abstract":"We consider the arrangement of vertices of a unit multidimensional cube, an affine subspace, and its orthogonal projections onto coordinate subspaces. Upper and lower bounds on the subspace dimension are given under which some orthogonal projection always preserves the incidence relation between the subspace and cube vertices. Some oblique projections are also considered. Moreover, a brief review of the history of the development of multidimensional descriptive geometry is given. Analytic and synthetic methods in geometry diverged since the 17th century. Although both synthesis and analysis are tangled, from this time forth many geometers as well as engineers keep up a nice distinction. One can find references to the idea of higher-dimensional spaces in the 18th-century works, but proper development has been since the middle of the 19th century. Soon such works have appeared in Russian. Next, mathematicians generalized their theories to many dimensions. Our new results are obtained by both analytic and synthetic methods. They illustrate the complexity of pseudo-Boolean programming problems because reducing the problem dimension by orthogonal projection meets obstacles in the worst case.","PeriodicalId":43239,"journal":{"name":"Vestnik Udmurtskogo Universiteta-Matematika Mekhanika Kompyuternye Nauki","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135686320","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
On the basis of piecewise quadratic interpolation, semi-analytical approximations of the normal derivative of the simple layer potential near and on the boundary of a two-dimensional domain are obtained. To calculate the integrals formed after the interpolation of the density function, exact integration over the variable $rho=(r^{2}-d^{2})^{1/2} $ is used, where $d$ and $r$ are the distances from the observed point to the boundary of the domain and to the boundary point of integration, respectively. The study proves the stable convergence of such approximations with cubic velocity uniformly near the boundary of the class $C^{5}$, as well as on the boundary itself. It is also proved that, by analogy with the exact function, the approximations suffer a discontinuity at the boundary, the magnitude of which is proportional to the values of the interpolated density function, but they can be extended on the boundary to functions that are continuous either on a closed internal border domain or on a closed external one. Theoretical conclusions about uniform convergence are confirmed by the results of calculating the normal derivative near the boundary of a unit circle.
{"title":"On one semi-analytical approximation of the normal derivative of the simple layer potential near the boundary of a two-dimensional domain","authors":"D.Yu. Ivanov","doi":"10.35634/vm230304","DOIUrl":"https://doi.org/10.35634/vm230304","url":null,"abstract":"On the basis of piecewise quadratic interpolation, semi-analytical approximations of the normal derivative of the simple layer potential near and on the boundary of a two-dimensional domain are obtained. To calculate the integrals formed after the interpolation of the density function, exact integration over the variable $rho=(r^{2}-d^{2})^{1/2} $ is used, where $d$ and $r$ are the distances from the observed point to the boundary of the domain and to the boundary point of integration, respectively. The study proves the stable convergence of such approximations with cubic velocity uniformly near the boundary of the class $C^{5}$, as well as on the boundary itself. It is also proved that, by analogy with the exact function, the approximations suffer a discontinuity at the boundary, the magnitude of which is proportional to the values of the interpolated density function, but they can be extended on the boundary to functions that are continuous either on a closed internal border domain or on a closed external one. Theoretical conclusions about uniform convergence are confirmed by the results of calculating the normal derivative near the boundary of a unit circle.","PeriodicalId":43239,"journal":{"name":"Vestnik Udmurtskogo Universiteta-Matematika Mekhanika Kompyuternye Nauki","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135686322","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this paper, we consider the integration of the negative order Korteweg-de Vries equation by the inverse scattering method. The evolution of the spectral data of the Sturm-Liouville operator with a potential associated with the solution of the negative order Korteweg-de Vries equation is determined. The obtained results make it possible to apply the method of inverse scattering problem to solve the negative order Korteweg-de Vries equation in the class of rapidly decreasing functions.
{"title":"Integration of the negative order Korteweg-de Vries equation by the inverse scattering method","authors":"G.U. Urazboev, I.I. Baltaeva, O.B. Ismoilov","doi":"10.35634/vm230309","DOIUrl":"https://doi.org/10.35634/vm230309","url":null,"abstract":"In this paper, we consider the integration of the negative order Korteweg-de Vries equation by the inverse scattering method. The evolution of the spectral data of the Sturm-Liouville operator with a potential associated with the solution of the negative order Korteweg-de Vries equation is determined. The obtained results make it possible to apply the method of inverse scattering problem to solve the negative order Korteweg-de Vries equation in the class of rapidly decreasing functions.","PeriodicalId":43239,"journal":{"name":"Vestnik Udmurtskogo Universiteta-Matematika Mekhanika Kompyuternye Nauki","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135686323","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The paper introduces the concept of a regulated function of several variables $fcolon Xtomathbb R$, where $Xsubseteq mathbb R^n$. The definition is based on the concept of a special partition of the set $X$ and the concept of oscillation of the function $f$ on the elements of the partition. It is shown that every function defined and continuous on the closure $X$ of the open bounded set $X_0subseteqmathbb R^n$, is regulated (belongs to the space $langle{rm G(}X),|cdot |rangle$). The completeness of the space ${rm G}(X)$ in the $sup$-norm $|cdot|$ is proved. This is the closure of the space of step functions. In the second part of the work, the space ${rm G}^J(X)$ is defined and studied, which differs from the space ${rm G}(X)$ in that its definition uses $J$-partitions instead of partitions, whose elements are Jordan measurable open sets. The properties of the space ${rm G}(X)$ listed above carry over to the space ${rm G}^J(X)$. In the final part of the paper, the notion of $J$-integrability of functions of several variables is defined. It is proved that if $X$ is a Jordan measurable closure of an open bounded set $X_0subseteqmathbb R^n$, and the function $fcolon Xtomathbb R$ is Riemann integrable, then it is $J$-integrable. In this case, the values of the integrals coincide. All functions $fin{rm G}^J(X)$ are $J$-integrable.
{"title":"On Banach spaces of regulated functions of several variables. An analogue of the Riemann integral","authors":"V.N. Baranov, V.I. Rodionov, A.G. Rodionova","doi":"10.35634/vm230301","DOIUrl":"https://doi.org/10.35634/vm230301","url":null,"abstract":"The paper introduces the concept of a regulated function of several variables $fcolon Xtomathbb R$, where $Xsubseteq mathbb R^n$. The definition is based on the concept of a special partition of the set $X$ and the concept of oscillation of the function $f$ on the elements of the partition. It is shown that every function defined and continuous on the closure $X$ of the open bounded set $X_0subseteqmathbb R^n$, is regulated (belongs to the space $langle{rm G(}X),|cdot |rangle$). The completeness of the space ${rm G}(X)$ in the $sup$-norm $|cdot|$ is proved. This is the closure of the space of step functions. In the second part of the work, the space ${rm G}^J(X)$ is defined and studied, which differs from the space ${rm G}(X)$ in that its definition uses $J$-partitions instead of partitions, whose elements are Jordan measurable open sets. The properties of the space ${rm G}(X)$ listed above carry over to the space ${rm G}^J(X)$. In the final part of the paper, the notion of $J$-integrability of functions of several variables is defined. It is proved that if $X$ is a Jordan measurable closure of an open bounded set $X_0subseteqmathbb R^n$, and the function $fcolon Xtomathbb R$ is Riemann integrable, then it is $J$-integrable. In this case, the values of the integrals coincide. All functions $fin{rm G}^J(X)$ are $J$-integrable.","PeriodicalId":43239,"journal":{"name":"Vestnik Udmurtskogo Universiteta-Matematika Mekhanika Kompyuternye Nauki","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135686321","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A mathematical model of the dynamics of the predator and prey populations in the form of a hybrid dynamical system consisting of two two-dimensional systems switching between each other is proposed. Switching of the systems allows us to reproduce a special refuge-regime when the prey number is very small and predators have complications to find preys. The sliding modes are studied using Filippov approach. Regularization of the system by using two switching lines to avoid chattering is provided. For the regularized model the limit sets are established. A scenario of the system self-organization preventing the unbounded populations' growth is proposed. A sensitivity study is carried out with respect to a parameter defining the switching lines. An important result of the research is that sufficiently small changing of the switching lines does not change the qualitative behavior of the system.
{"title":"A hybrid model of population dynamics with refuge-regime: regularization and self-organization","authors":"A.N. Kirillov, A.M. Sazonov","doi":"10.35634/vm230306","DOIUrl":"https://doi.org/10.35634/vm230306","url":null,"abstract":"A mathematical model of the dynamics of the predator and prey populations in the form of a hybrid dynamical system consisting of two two-dimensional systems switching between each other is proposed. Switching of the systems allows us to reproduce a special refuge-regime when the prey number is very small and predators have complications to find preys. The sliding modes are studied using Filippov approach. Regularization of the system by using two switching lines to avoid chattering is provided. For the regularized model the limit sets are established. A scenario of the system self-organization preventing the unbounded populations' growth is proposed. A sensitivity study is carried out with respect to a parameter defining the switching lines. An important result of the research is that sufficiently small changing of the switching lines does not change the qualitative behavior of the system.","PeriodicalId":43239,"journal":{"name":"Vestnik Udmurtskogo Universiteta-Matematika Mekhanika Kompyuternye Nauki","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135686324","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This article is devoted to studying the structure of topological left (or right) quasigroups, which play a great role in noncommutative geometry. Quotient and transversal mappings are important in the theory of differentiable manifolds and topological manifolds. Their transversal and quotient mappings are investigated. Necessary and sufficient conditions for their continuity are scrutinized. Examples are given. Homogeneous spaces are investigated related to topological quasigroups and their subquasigroups. For this purpose, the products of special types of topological left (or right) quasigroups, which are called smashed, are investigated. They are used to describe an extensive family of topological nondiscrete left (or right) quasigroups for which transversal mappings are continuous.
{"title":"Quotient and transversal mappings for topological quasigroups","authors":"S.V. Ludkowski","doi":"10.35634/vm230308","DOIUrl":"https://doi.org/10.35634/vm230308","url":null,"abstract":"This article is devoted to studying the structure of topological left (or right) quasigroups, which play a great role in noncommutative geometry. Quotient and transversal mappings are important in the theory of differentiable manifolds and topological manifolds. Their transversal and quotient mappings are investigated. Necessary and sufficient conditions for their continuity are scrutinized. Examples are given. Homogeneous spaces are investigated related to topological quasigroups and their subquasigroups. For this purpose, the products of special types of topological left (or right) quasigroups, which are called smashed, are investigated. They are used to describe an extensive family of topological nondiscrete left (or right) quasigroups for which transversal mappings are continuous.","PeriodicalId":43239,"journal":{"name":"Vestnik Udmurtskogo Universiteta-Matematika Mekhanika Kompyuternye Nauki","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135686319","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We present a modification of the developed hexahedral mesh generator from voxel data which allows constructing adaptive computational meshes. Construction of the refinement field is based on geometry features of the described model when it has a large thickness difference in dimensions or small and thin areas. A universal criterion for cells refinement is proposed which gives the possibility of its use in the case of volumetric (voxel) and surface (STL) representations of the model geometry. The refinement templates that provide conformal mesh closure are described. The results of the algorithm performance are given.
{"title":"Generation of adaptive hexahedral meshes from surface and voxel geometric models","authors":"A.S. Karavaev, S.P. Kopysov","doi":"10.35634/vm230310","DOIUrl":"https://doi.org/10.35634/vm230310","url":null,"abstract":"We present a modification of the developed hexahedral mesh generator from voxel data which allows constructing adaptive computational meshes. Construction of the refinement field is based on geometry features of the described model when it has a large thickness difference in dimensions or small and thin areas. A universal criterion for cells refinement is proposed which gives the possibility of its use in the case of volumetric (voxel) and surface (STL) representations of the model geometry. The refinement templates that provide conformal mesh closure are described. The results of the algorithm performance are given.","PeriodicalId":43239,"journal":{"name":"Vestnik Udmurtskogo Universiteta-Matematika Mekhanika Kompyuternye Nauki","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135686212","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This article considers inverse problems for a fourth-order hyperbolic equation with involution. The existence and uniqueness of a solution of the studied inverse problems is established by the method of separation of variables. To apply the method of separation of variables, we prove the Riesz basis property of the eigenfunctions for a fourth-order differential operator with involution in the space ${{L}_{2}}(-1,1)$. For proving theorems on the existence and uniqueness of a solution, we widely use the Bessel inequality for the coefficients of expansions into a Fourier series in the space ${{L}_{2}}(-1,1)$. A significant dependence of the existence of a solution on the equation coefficient $alpha$ is shown. In each of the cases $alpha <-1$, $alpha >1$, $-1
{"title":"Inverse problems for the beam vibration equation with involution","authors":"A.B. Imanbetova, Abdissalam Sarsenbi, Bolat Seilbekov","doi":"10.35634/vm230305","DOIUrl":"https://doi.org/10.35634/vm230305","url":null,"abstract":"This article considers inverse problems for a fourth-order hyperbolic equation with involution. The existence and uniqueness of a solution of the studied inverse problems is established by the method of separation of variables. To apply the method of separation of variables, we prove the Riesz basis property of the eigenfunctions for a fourth-order differential operator with involution in the space ${{L}_{2}}(-1,1)$. For proving theorems on the existence and uniqueness of a solution, we widely use the Bessel inequality for the coefficients of expansions into a Fourier series in the space ${{L}_{2}}(-1,1)$. A significant dependence of the existence of a solution on the equation coefficient $alpha$ is shown. In each of the cases $alpha <-1$, $alpha >1$, $-1<alpha<1$ representations of solutions in the form of Fourier series in terms of eigenfunctions of boundary value problems for a fourth-order equation with involution are written out.","PeriodicalId":43239,"journal":{"name":"Vestnik Udmurtskogo Universiteta-Matematika Mekhanika Kompyuternye Nauki","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135686327","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this article, we study the growth of solutions of homogeneous and non-homogeneous complex linear differential equations where the coefficients are analytic functions in the extended complex plane except a finite singular point with finite logarithmic order. We extend some previous results obtained very recently by Fettouch and Hamouda.
{"title":"On the growth of solutions of complex linear differential equations with analytic coefficients in $overline{mathbb{C}}backslash{z_{0}}$ of finite logarithmic order","authors":"Abdelkader Dahmani, Benharrat Belaïdi","doi":"10.35634/vm230303","DOIUrl":"https://doi.org/10.35634/vm230303","url":null,"abstract":"In this article, we study the growth of solutions of homogeneous and non-homogeneous complex linear differential equations where the coefficients are analytic functions in the extended complex plane except a finite singular point with finite logarithmic order. We extend some previous results obtained very recently by Fettouch and Hamouda.","PeriodicalId":43239,"journal":{"name":"Vestnik Udmurtskogo Universiteta-Matematika Mekhanika Kompyuternye Nauki","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135686318","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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