{"title":"Smooth Rigidity for Higher-Dimensional Contact Anosov Flows","authors":"","doi":"10.1007/s11253-024-02266-2","DOIUrl":"https://doi.org/10.1007/s11253-024-02266-2","url":null,"abstract":"<p>We apply the technique of matching functions in the setting of contact Anosov flows satisfying a bunching assumption. This allows us to generalize the 3-dimensional rigidity result of Feldman and Ornstein [<em>Ergodic Theory Dynam. Syst.</em>, <strong>7</strong>, No. 1, 49–72 (1987)]. Namely, we show that if two Anosov flow of this kind are <em>C</em><sup>0</sup> conjugate, then they are <em>C</em><sup><em>r</em></sup> conjugate for some <em>r</em> ∈ [1<em>,</em> 2) or even <em>C</em><sup>∞</sup> conjugate under certain additional assumptions. This, e.g., applies to geodesic flows on compact Riemannian manifolds of 1<em>/</em>4-pinched negative sectional curvature. We can also use our result to recover Hamendstädt’s marked length spectrum rigidity result for real hyperbolic manifolds.</p>","PeriodicalId":49406,"journal":{"name":"Ukrainian Mathematical Journal","volume":"30 1","pages":""},"PeriodicalIF":0.5,"publicationDate":"2024-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139923527","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":"Cohomology and Formal Deformations of n-Hom–Lie Color Algebras","authors":"K. Abdaoui, R. Gharbi, S. Mabrouk, A. Makhlouf","doi":"10.1007/s11253-024-02264-4","DOIUrl":"https://doi.org/10.1007/s11253-024-02264-4","url":null,"abstract":"<p>We provide a cohomology of <i>n</i>-Hom–Lie color algebras, in particular, a cohomology governing oneparameter formal deformations. Then we also study formal deformations of the <i>n</i>-Hom–Lie color algebras and introduce the notion of Nijenhuis operator on an <i>n</i>-Hom–Lie color algebra, which may give rise to infinitesimally trivial (<i>n −</i> 1)th-order deformations. Furthermore, in connection with Nijenhuis operators, we introduce and discuss the notion of product structure on <i>n</i>-Hom–Lie color algebras.</p>","PeriodicalId":49406,"journal":{"name":"Ukrainian Mathematical Journal","volume":"16 1","pages":""},"PeriodicalIF":0.5,"publicationDate":"2024-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139923528","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}
Ghazala Gulshan, Hüseyin Budak, Rashida Hussain, Muhammad Aamir Ali
{"title":"New Quantum Hermite–Hadamard-Type Inequalities for p-Convex Functions Involving Recently Defined Quantum Integrals","authors":"Ghazala Gulshan, Hüseyin Budak, Rashida Hussain, Muhammad Aamir Ali","doi":"10.1007/s11253-024-02267-1","DOIUrl":"https://doi.org/10.1007/s11253-024-02267-1","url":null,"abstract":"<p>We develop new Hermite–Hadamard-type integral inequalities for <i>p</i>-convex functions in the context of <i>q</i>-calculus by using the concept of recently defined <i>T</i><sub><i>q</i></sub>-integrals. Then the obtained Hermite–Hadamard inequality for <i>p</i>-convex functions is used to get a new Hermite–Hadamard inequality for coordinated <i>p</i>-convex functions. Furthermore, we present some examples to demonstrate the validity of our main results. We hope that the proposed ideas and techniques may stimulate further research in this field.</p>","PeriodicalId":49406,"journal":{"name":"Ukrainian Mathematical Journal","volume":"153 1","pages":""},"PeriodicalIF":0.5,"publicationDate":"2024-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139923788","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}
David Kazhdan, Amichai Lampert, Alexander Polishchuk
{"title":"Schmidt Rank and Singularities","authors":"David Kazhdan, Amichai Lampert, Alexander Polishchuk","doi":"10.1007/s11253-024-02270-6","DOIUrl":"https://doi.org/10.1007/s11253-024-02270-6","url":null,"abstract":"<p>We revisit Schmidt’s theorem connecting the Schmidt rank of a tensor with the codimension of a certain variety and adapt the proof to the case of arbitrary characteristic. We also establish a sharper result for this kind for homogeneous polynomials, assuming that the characteristic does not divide the degree. Further, we use this to relate the Schmidt rank of a homogeneous polynomial (resp., a collection of homogeneous polynomials of the same degree) with the codimension of the singular locus of the corresponding hypersurface (resp., intersection of hypersurfaces). This gives an effective version of Ananyan–Hochster’s theorem [<i>J. Amer. Math. Soc.</i>, <b>33</b>, No. 1, 291–309 (2020), Theorem A].</p>","PeriodicalId":49406,"journal":{"name":"Ukrainian Mathematical Journal","volume":"234 1","pages":""},"PeriodicalIF":0.5,"publicationDate":"2024-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139923655","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":"Convergence of Baum–Katz Series for Sums Whose Terms are Elements of a Linear mth Order Autoregressive Sequence","authors":"Maryna Ilienko, Anastasiia Polishchuk","doi":"10.1007/s11253-024-02269-z","DOIUrl":"https://doi.org/10.1007/s11253-024-02269-z","url":null,"abstract":"<p>We establish necessary and sufficient conditions for the convergence of the Baum–Katz series for the sums of elements of linear <i>m</i>th order autoregressive sequences of random variables.</p>","PeriodicalId":49406,"journal":{"name":"Ukrainian Mathematical Journal","volume":"1 1","pages":""},"PeriodicalIF":0.5,"publicationDate":"2024-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139923531","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":"Embeddings Into Countably Compact Hausdorff Spaces","authors":"Taras Banakh, Serhii Bardyla, Alex Ravsky","doi":"10.1007/s11253-023-02254-y","DOIUrl":"https://doi.org/10.1007/s11253-023-02254-y","url":null,"abstract":"<p>We consider the problem of characterization of topological spaces embedded into countably compact Hausdorff topological spaces. We study the separation axioms for subspaces of Hausdorff countably compact topological spaces and construct an example of a regular separable scattered topological space that cannot be embedded into an Urysohn countably compact topological space.</p>","PeriodicalId":49406,"journal":{"name":"Ukrainian Mathematical Journal","volume":"46 1","pages":""},"PeriodicalIF":0.5,"publicationDate":"2023-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138567796","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}
Leonid Bedratyuk, Anatolii Petravchuk, Evhen Chapovskyi
{"title":"Centralizers of Linear and Locally Nilpotent Derivations","authors":"Leonid Bedratyuk, Anatolii Petravchuk, Evhen Chapovskyi","doi":"10.1007/s11253-023-02255-x","DOIUrl":"https://doi.org/10.1007/s11253-023-02255-x","url":null,"abstract":"<p>Let 𝕂 be an algebraically closed field of characteristic zero, let 𝕂[<i>x</i><sub>1</sub>,…,<i>x</i><sub><i>n</i></sub>] be the polynomial algebra, and let <i>W</i><sub><i>n</i></sub>(𝕂) be the Lie algebra of all 𝕂-derivations on 𝕂[<i>x</i><sub>1</sub>,…,<i>x</i><sub><i>n</i></sub>]<i>.</i> For any derivation <i>D</i> with linear components, we describe the centralizer of <i>D</i> in <i>W</i><sub><i>n</i></sub>(𝕂) and propose an algorithm for finding the generators of this centralizer regarded as a module over the ring of constants of the derivation <i>D</i> in the case where <i>D</i> is a basic Weitzenböck derivation. In a more general case where a finitely generated integral domain <i>A</i> over the field 𝕂 is considered instead of the polynomial algebra 𝕂[<i>x</i><sub>1</sub>,…,<i>x</i><sub><i>n</i></sub>] and <i>D</i> is a locally nilpotent derivation on <i>A,</i> we prove that the centralizer C<sub>Der<i>A</i></sub>(<i>D</i>) of <i>D</i> in the Lie algebra Der<i>A</i> of all 𝕂-derivations on <i>A</i> is a “large” subalgebra of Der <i>A.</i> Specifically, the rank of C<sub>Der<i>A</i></sub>(<i>D</i>) over <i>A</i> is equal to the transcendence degree of the field of fractions Frac(<i>A</i>) over the field 𝕂.</p>","PeriodicalId":49406,"journal":{"name":"Ukrainian Mathematical Journal","volume":"46 1","pages":""},"PeriodicalIF":0.5,"publicationDate":"2023-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140889268","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 Modulus of Smoothness for Some Banach Function Spaces","authors":"Ramazan Akgün","doi":"10.1007/s11253-023-02253-z","DOIUrl":"https://doi.org/10.1007/s11253-023-02253-z","url":null,"abstract":"<p>Based on the Steklov operator, we consider a modulus of smoothness for functions in some Banach function spaces, which can be not translation invariant, and establish its main properties. A constructive characterization of the Lipschitz class is obtained with the help of the Jackson-type direct theorem and the inverse theorem on trigonometric approximation. As an application, we present several examples of related (weighted) function spaces.</p>","PeriodicalId":49406,"journal":{"name":"Ukrainian Mathematical Journal","volume":"170 1","pages":""},"PeriodicalIF":0.5,"publicationDate":"2023-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138568171","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":"Adomian’s Decomposition Method in the Theory of Nonlinear Autonomous Boundary-Value Problems","authors":"Oleksandr Boichuk, Serhii Chuiko, Dar’ya Diachenko","doi":"10.1007/s11253-023-02256-w","DOIUrl":"https://doi.org/10.1007/s11253-023-02256-w","url":null,"abstract":"<p>For a nonlinear autonomous boundary-value problem posed for an ordinary differential equation in the critical case, we establish constructive conditions for its solvability and propose a scheme for the construction of solutions based on the use of Adomian’s decomposition method.</p>","PeriodicalId":49406,"journal":{"name":"Ukrainian Mathematical Journal","volume":"12 1","pages":""},"PeriodicalIF":0.5,"publicationDate":"2023-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138567810","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":"Generalized Weakly Demicompact and S-Demicompact Linear Relations and Their Spectral Properties","authors":"Majed Fakhfakh, Aref Jeribi","doi":"10.1007/s11253-023-02261-z","DOIUrl":"https://doi.org/10.1007/s11253-023-02261-z","url":null,"abstract":"<p>We extend the concept of generalized weakly demicompact and relatively weakly demicompact operators on linear relations and present some outstanding results. Moreover, we address the theory of Fredholm and upper semi-Fredholm relations and make an attempt to establish connections with these operators.</p>","PeriodicalId":49406,"journal":{"name":"Ukrainian Mathematical Journal","volume":"129 1","pages":""},"PeriodicalIF":0.5,"publicationDate":"2023-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138559556","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}