{"title":"Estimates for the Norm of the Hardy Operator in Operator Ideals","authors":"E. N. Lomakina, M. G. Nasyrova","doi":"10.1134/s0037446624020083","DOIUrl":"https://doi.org/10.1134/s0037446624020083","url":null,"abstract":"<p>We find the conditions for a compact Hardy operator in Lorentz spaces\u0000to belong to the operator ideals generated by sequences of <span>( s )</span>-numbers.\u0000We obtain some estimates of the norms of the Hardy operator in these ideals in terms of integral\u0000expressions depending on the weight functions of the operator.</p>","PeriodicalId":49533,"journal":{"name":"Siberian Mathematical Journal","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2024-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140299821","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"A Family with a Single Minimal but Not Least Numbering","authors":"M. Kh. Faizrahmanov","doi":"10.1134/s0037446624020125","DOIUrl":"https://doi.org/10.1134/s0037446624020125","url":null,"abstract":"<p>We prove the existence of a family of computably enumerable sets that,\u0000up to equivalence,\u0000has a unique computable minimal but not least numbering.</p>","PeriodicalId":49533,"journal":{"name":"Siberian Mathematical Journal","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2024-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140299651","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Craig’s Interpolation Property in Pretabular Logics","authors":"L. L. Maksimova, V. F. Yun","doi":"10.1134/s0037446624020095","DOIUrl":"https://doi.org/10.1134/s0037446624020095","url":null,"abstract":"<p>All pretabular extensions of the minimal logic were described and\u0000the tabularity problem was solved earlier. As turned out, in total, there are seven\u0000pretabular logics over the minimal logic. It was proved that four of them have\u0000Craig’s interpolation property (CIP) and two do not. In the present article,\u0000we solve the problem of CIP in the seventh logic. We prove that\u0000it has Craig’s interpolation property.</p>","PeriodicalId":49533,"journal":{"name":"Siberian Mathematical Journal","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2024-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140299652","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"On the Optimal Recovery of One Family of Operators on a Class of Functions from Approximate Information about Its Spectrum","authors":"E. V. Abramova, E. O. Sivkova","doi":"10.1134/s0037446624020010","DOIUrl":"https://doi.org/10.1134/s0037446624020010","url":null,"abstract":"<p>We find explicit expressions for optimal recovery methods in the problem\u0000of recovering the values of continuous linear operators on a Sobolev function class\u0000from the following information: The Fourier transform of functions is known approximately\u0000on some measurable subset of the finite-dimensional space on which the functions are\u0000defined. As corollaries, we obtain optimal methods for recovering the solution to the heat\u0000equation and solving the Dirichlet problem for a half-space.</p>","PeriodicalId":49533,"journal":{"name":"Siberian Mathematical Journal","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2024-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140297694","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Teichmüller’s Modulsatz and the Variation of the Dirichlet Integral","authors":"V. N. Dubinin","doi":"10.1134/s0037446624020058","DOIUrl":"https://doi.org/10.1134/s0037446624020058","url":null,"abstract":"<p>We show that\u0000changing the level curve of a harmonic function\u0000with the classical Hadamard variation with a small parameter\u0000entails a change in the Dirichlet integral of the function\u0000which is quadratic in the parameter.\u0000As a corollary,\u0000we supplement the well-known theorem of Teichmüller\u0000about the sum of moduli of doubly connected domains\u0000into which an annulus is subdivided\u0000by a continuum that differs little from a concentric circle.</p>","PeriodicalId":49533,"journal":{"name":"Siberian Mathematical Journal","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2024-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140299537","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Novikov $ ��_{2} $ -Graded Algebras with an Associative 0-Component","authors":"A. S. Panasenko, V. N. Zhelyabin","doi":"10.1134/s0037446624020150","DOIUrl":"https://doi.org/10.1134/s0037446624020150","url":null,"abstract":"<p>In 1974 Kharchenko proved that if a <span>( 0 )</span>-component of an <span>( n )</span>-graded associative algebra is PI then this algebra is PI.\u0000In the Novikov algebras of characteristic 0 the existence of a polynomial identity is equivalent to the solvability of the commutator ideal.\u0000We study a <span>( _{2} )</span>-graded Novikov algebra <span>( N=A+M )</span> and prove that if the characteristic of the basic field is not 2 or 3\u0000and its 0-component <span>( A )</span> is associative or Lie-nilpotent of index 3 then\u0000the commutator ideal <span>( [N,N] )</span> is solvable.</p>","PeriodicalId":49533,"journal":{"name":"Siberian Mathematical Journal","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2024-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140299572","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Birman–Hilden Bundles. II","authors":"A. V. Malyutin","doi":"10.1134/s0037446624020101","DOIUrl":"https://doi.org/10.1134/s0037446624020101","url":null,"abstract":"<p>We study the structure of self-homeomorphism groups of fibered manifolds.\u0000A fibered topological space\u0000is a Birman–Hilden space\u0000whenever in each isotopic pair of its fiber-preserving\u0000(taking each fiber to a fiber)\u0000self-homeomorphisms\u0000the homeomorphisms are also fiber-isotopic\u0000(isotopic through fiber-preserving homeomorphisms).\u0000We prove in particular that\u0000the Birman–Hilden class contains\u0000all compact connected locally trivial surface bundles over the circle,\u0000including nonorientable ones and those with nonempty boundary,\u0000as well as all closed orientable Haken 3-manifold bundles over the circle,\u0000including nonorientable ones.</p>","PeriodicalId":49533,"journal":{"name":"Siberian Mathematical Journal","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2024-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140299759","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"On the Qualitative Properties of a Solution to a System of Infinite Nonlinear Algebraic Equations","authors":"M. H. Avetisyan, Kh. A. Khachatryan","doi":"10.1134/s0037446624020186","DOIUrl":"https://doi.org/10.1134/s0037446624020186","url":null,"abstract":"<p>We study and solve some class of infinite systems of\u0000algebraic equations with monotone nonlinearity and Toeplitz-type matrices.\u0000Such systems\u0000for the specific representations of nonlinearities arise in the discrete problems of\u0000dynamic theory of clopen <span>( p )</span>-adic strings for a scalar field of tachyons,\u0000the mathematical theory of spatio-temporal spread of an epidemic, radiation transfer theory\u0000in inhomogeneous media, and the kinetic theory of gases in the framework of the modified Bhatnagar–Gross–Krook\u0000model. The noncompactness of the corresponding operator in the bounded sequence space\u0000and the criticality property (the presence of trivial nonphysical\u0000solutions) is a distinctive feature of these systems.\u0000For these reasons, the use of the well-known classical principles of existence\u0000of fixed points for such equations do not lead to the desired results.\u0000Constructing some invariant cone segments for the corresponding\u0000nonlinear operator, we prove the existence and uniqueness of a nontrivial\u0000nonnegative solution in the bounded sequence space.\u0000Also, we study the asymptotic behavior of the solution at <span>( pminfty )</span>.\u0000In particular, we prove that the limit at <span>( pminfty )</span> of a solution is finite.\u0000Also, we show that the difference between\u0000this limit and a solution belongs to <span>( l_{1} )</span>.\u0000By way of illustration, we provide some special applied examples.</p>","PeriodicalId":49533,"journal":{"name":"Siberian Mathematical Journal","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2024-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140297587","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Homogenization of the Scalar Boundary Value Problem in a Thin Periodically Broken Cylinder","authors":"S. A. Nazarov, A. S. Slutskii","doi":"10.1134/s0037446624020113","DOIUrl":"https://doi.org/10.1134/s0037446624020113","url":null,"abstract":"<p>Homogenization of the Neumann problem for a differential equation\u0000in a periodically broken multidimensional cylinder\u0000leads to a second-order ordinary differential equation.\u0000We study asymptotics for the coefficient of the averaged operator\u0000in the case of small transverse cross-sections.\u0000The main asymptotic term depends on\u0000the “area” of cross-sections of the links,\u0000their lengths,\u0000and the coefficient matrix of the original operator.\u0000We find the characteristics of kink zones which affect correction terms,\u0000while the asymptotic remainder becomes exponentially small.\u0000The justification of the asymptotics\u0000is based on Friedrichs’s inequality\u0000with a coefficient independent of both small parameters:\u0000the period of fractures and the relative diameter of cross-sections.</p>","PeriodicalId":49533,"journal":{"name":"Siberian Mathematical Journal","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2024-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140299754","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Algebras of Binary Formulas for Weakly Circularly Minimal Theories with Trivial Definable Closure","authors":"B. Sh. Kulpeshov","doi":"10.1134/s0037446624020071","DOIUrl":"https://doi.org/10.1134/s0037446624020071","url":null,"abstract":"<p>We describe the algebras of binary formulas for\u0000countably categorical weakly circularly minimal theories with 1-transitive nonprimitive\u0000automorphism group and trivial definable closure\u0000having convexity rank 1. We find some criterion for commutativity of the algebras.</p>","PeriodicalId":49533,"journal":{"name":"Siberian Mathematical Journal","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2024-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140299767","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}