{"title":"Gromov’s Oka Principle, Fiber Bundles and the Conformal Module","authors":"Burglind Jöricke","doi":"10.1007/s40306-021-00452-z","DOIUrl":"10.1007/s40306-021-00452-z","url":null,"abstract":"<div><p>The conformal module of conjugacy classes of braids is an invariant that appeared earlier than the entropy of conjugacy classes of braids, and is inversely proportional to the entropy. Using the relation between the two invariants, we give a short conceptional proof of an earlier result on the conformal module. Mainly, we consider situations, when the conformal module of conjugacy classes of braids serves as obstruction for the existence of homotopies (or isotopies) of smooth objects involving braids to the respective holomorphic objects, and present theorems on the restricted validity of Gromov’s Oka principle in these situations.</p></div>","PeriodicalId":45527,"journal":{"name":"Acta Mathematica Vietnamica","volume":"47 2","pages":"375 - 440"},"PeriodicalIF":0.5,"publicationDate":"2022-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47749406","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}
{"title":"Hybrid Inertial Contraction Algorithms for Solving Variational Inequalities with Fixed Point Constraints in Hilbert Spaces","authors":"Pham Ngoc Anh","doi":"10.1007/s40306-021-00467-6","DOIUrl":"10.1007/s40306-021-00467-6","url":null,"abstract":"<div><p>In this paper, basing on the forward-backward method and inertial techniques, we introduce a new algorithm for solving a variational inequality problem over the fixed point set of a nonexpansive mapping. The strong convergence of the algorithm is established under strongly monotone and Lipschitz continuous assumptions imposed on the cost mapping. As an application, we also apply and analyze our algorithm to solve a convex minimization problem of the sum of two convex functions.</p></div>","PeriodicalId":45527,"journal":{"name":"Acta Mathematica Vietnamica","volume":"47 4","pages":"743 - 753"},"PeriodicalIF":0.5,"publicationDate":"2022-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45827527","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}
{"title":"Skew Polynomial Rings: the Schreier Technique","authors":"Phạm Ngọc Ánh","doi":"10.1007/s40306-021-00466-7","DOIUrl":"10.1007/s40306-021-00466-7","url":null,"abstract":"<div><p>Schreier bases are introduced and used to show that skew polynomial rings are free ideal rings, i.e., rings whose one-sided ideals are free of unique rank, as well as to compute a rank of one-sided ideals together with a description of corresponding bases. The latter fact, a so-called Schreier-Lewin formula (Lewin <i>Trans. Am. Math. Soc.</i> <b>145</b>, 455–465 1969), is a basic tool determining a module type of perfect localizations which reveal a close connection between classical Leavitt algebras, skew polynomial rings, and free associative algebras.</p></div>","PeriodicalId":45527,"journal":{"name":"Acta Mathematica Vietnamica","volume":"47 1","pages":"5 - 17"},"PeriodicalIF":0.5,"publicationDate":"2022-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s40306-021-00466-7.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50504925","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"The First Syzygy of Hibi Rings Associated with Planar Distributive Lattices","authors":"Priya Das, Himadri Mukherjee","doi":"10.1007/s40306-021-00463-w","DOIUrl":"10.1007/s40306-021-00463-w","url":null,"abstract":"<div><p>In this article, we give explicit minimal generators of the first syzygy of the Hibi ring for a planar distributive lattice in terms of sublattices. We also give a characterization when it is linearly related and derive an exact formula for the first Betti number of a planar distributive lattice.</p></div>","PeriodicalId":45527,"journal":{"name":"Acta Mathematica Vietnamica","volume":"47 3","pages":"689 - 707"},"PeriodicalIF":0.5,"publicationDate":"2022-01-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s40306-021-00463-w.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46115988","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Gröbner Bases of Toric Ideals Associated with Matroids","authors":"Ken-ichi Hayase, Takayuki Hibi, Koyo Katsuno, Kazuki Shibata","doi":"10.1007/s40306-021-00468-5","DOIUrl":"10.1007/s40306-021-00468-5","url":null,"abstract":"<div><p>In 1980, White conjectured that the toric ideal of a matroid is generated by quadratic binomials corresponding to a symmetric exchange. In this paper, we compute Gröbner bases of toric ideals associated with matroids and show that, for every matroid on ground sets of size at most seven except for two matroids, Gröbner bases of toric ideals consist of quadratic binomials corresponding to a symmetric exchange.</p></div>","PeriodicalId":45527,"journal":{"name":"Acta Mathematica Vietnamica","volume":"47 4","pages":"775 - 779"},"PeriodicalIF":0.5,"publicationDate":"2022-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42379930","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}
{"title":"q-Analogue of a Kantorovitch Variant of an Operator Defined by Stancu","authors":"P. N. Agrawal, Arun Kajla, Abhishek Kumar","doi":"10.1007/s40306-021-00472-9","DOIUrl":"10.1007/s40306-021-00472-9","url":null,"abstract":"<div><p>The purpose of this paper is to introduce a new kind of <i>q</i> −Stancu-Kantorovich type operators and study its various approximation properties. We establish some local direct theorems, e.g., Voronovskaja type asymptotic theorem, global approximation and an estimate of error by means of the Lipschitz type maximal function and the Peetre K-functional. We also consider a <i>n</i> th-order generalization of these operators and study its approximation properties. Next, we define a bivariate case of these operators and investigate the order of convergence by means of moduli of continuity and the elements of Lipschitz class. Furthermore, we consider the associated Generalized Boolean Sum (GBS) operators and examine the approximation degree for functions in a Bögel space. Some numerical examples to illustrate the convergence of these operators to certain functions are also given.</p></div>","PeriodicalId":45527,"journal":{"name":"Acta Mathematica Vietnamica","volume":"47 4","pages":"781 - 816"},"PeriodicalIF":0.5,"publicationDate":"2022-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43534999","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}
{"title":"A Note on Generalized Derivations of Order 2 and Multilinear Polynomials in Prime Rings","authors":"Basudeb Dhara, Sukhendu Kar, Swarup Kuila","doi":"10.1007/s40306-021-00471-w","DOIUrl":"10.1007/s40306-021-00471-w","url":null,"abstract":"<div><p>Let <i>R</i> be a prime ring of char(<i>R</i>)≠ 2, <i>U</i> its Utumi ring of quotients and center <i>C</i> = <i>Z</i>(<i>U</i>) its extended centroid, <i>I</i> a both sided ideal of <i>R</i>, <i>f</i>(<i>x</i><sub>1</sub>,…,<i>x</i><sub><i>n</i></sub>) a multilinear polynomial over <i>C</i>, that is noncentral-valued on <i>R</i>, <i>F</i>, <i>G</i> be two generalized derivations of <i>R</i> and <i>d</i> be a derivation of <i>R</i>. Let <i>f</i>(<i>I</i>) be the set of all evaluations of the multilinear polynomial <i>f</i>(<i>x</i><sub>1</sub>,…,<i>x</i><sub><i>n</i></sub>) in <i>I</i>. If @@@ for all <i>u</i> ∈ <i>f</i>(<i>I</i>), then all possible forms of the maps are determined. As an application of this result, we also study the commutator identity [<i>F</i><sup>2</sup>(<i>u</i>)<i>u</i>,<i>G</i><sup>2</sup>(<i>v</i>)<i>v</i>] = 0 for all <i>u</i>,<i>v</i> ∈ <i>f</i>(<i>I</i>), where <i>F</i> and <i>G</i> are two generalized derivations of <i>R</i>.</p></div>","PeriodicalId":45527,"journal":{"name":"Acta Mathematica Vietnamica","volume":"47 4","pages":"755 - 773"},"PeriodicalIF":0.5,"publicationDate":"2022-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45780664","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}
{"title":"Maximal Generating Degrees of Powers of Homogeneous Ideals","authors":"Le Tuan Hoa","doi":"10.1007/s40306-021-00469-4","DOIUrl":"10.1007/s40306-021-00469-4","url":null,"abstract":"<div><p>The degree excess function <i>𝜖</i>(<i>I</i>; <i>n</i>) is the difference between the maximal generating degree <i>d</i>(<i>I</i><sup><i>n</i></sup>) of the n-th power of a homogeneous ideal <i>I</i> of a polynomial ring and <i>p</i>(<i>I</i>)<i>n</i>, where <i>p</i>(<i>I</i>) is the leading coefficient of the asymptotically linear function <i>d</i>(<i>I</i><sup><i>n</i></sup>). It is shown that any non-increasing numerical function can be realized as a degree excess function, and there is a monomial ideal <i>I</i> whose <i>𝜖</i>(<i>I</i>; <i>n</i>) has exactly a given number of local maxima. In the case of monomial ideals, an upper bound on <i>𝜖</i>(<i>I</i>; <i>n</i>) is provided. As an application, it is shown that in the worst case, the so-called stability index of the Castelnuovo-Mumford regularity of a monomial ideal <i>I</i> must be at least an exponential function of the number of variables.</p></div>","PeriodicalId":45527,"journal":{"name":"Acta Mathematica Vietnamica","volume":"47 1","pages":"19 - 37"},"PeriodicalIF":0.5,"publicationDate":"2022-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46991186","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}
{"title":"Lelong Number and the Log Canonical Thresholds of Plurisubharmonic Functions on Analytic Subsets","authors":"Le Mau Hai, Pham Hoang Hiep, Trinh Tung","doi":"10.1007/s40306-021-00465-8","DOIUrl":"10.1007/s40306-021-00465-8","url":null,"abstract":"<div><p>The aim of this paper is to introduce the notion of Lelong number and the log canonical thresholds of plurisubharmonic functions on analytic subsets <i>A</i> in an open subset Ω of <span>(mathbb {C}^{n})</span>. Next, we establish some results about the relationship between these quantities in the relation with the analyticity of <i>A</i>.</p></div>","PeriodicalId":45527,"journal":{"name":"Acta Mathematica Vietnamica","volume":"47 1","pages":"223 - 241"},"PeriodicalIF":0.5,"publicationDate":"2022-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50452378","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}
{"title":"Lelong Number and the Log Canonical Thresholds of Plurisubharmonic Functions on Analytic Subsets","authors":"L. M. Hai, Phạm Hoàng Hiệp, Trinh Tung","doi":"10.1007/s40306-021-00465-8","DOIUrl":"https://doi.org/10.1007/s40306-021-00465-8","url":null,"abstract":"","PeriodicalId":45527,"journal":{"name":"Acta Mathematica Vietnamica","volume":"47 1","pages":"223 - 241"},"PeriodicalIF":0.5,"publicationDate":"2022-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"52714281","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}