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Some relations between complex structures on compact nilmanifolds and flag manifolds 紧零流形与标志流形上复结构的若干关系
IF 0.2 4区 数学
Hiroshima Mathematical Journal Pub Date : 2021-11-01 DOI: 10.32917/h2020027
Takumi Yamada
{"title":"Some relations between complex structures on compact nilmanifolds and flag manifolds","authors":"Takumi Yamada","doi":"10.32917/h2020027","DOIUrl":"https://doi.org/10.32917/h2020027","url":null,"abstract":"In this paper, we first consider relations between signatures of pseudoKähler metrics on a flag manifold and complex structures on a nilpotent Lie algebra corresponding to the flag manifold. On the nilpotent Lie algebra, we also consider complex structures which do not correspond to invariant complex structures on the flag manifold.","PeriodicalId":55054,"journal":{"name":"Hiroshima Mathematical Journal","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41992206","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}
引用次数: 0
Estimates for eigenvalues of weighted Laplacian and weighted $p$-Laplacian 加权拉普拉斯算子和加权p -拉普拉斯算子的特征值估计
IF 0.2 4区 数学
Hiroshima Mathematical Journal Pub Date : 2021-11-01 DOI: 10.32917/h2020086
Feng Du, Jing Mao, Qiaoling Wang, C. Xia
{"title":"Estimates for eigenvalues of weighted Laplacian and weighted $p$-Laplacian","authors":"Feng Du, Jing Mao, Qiaoling Wang, C. Xia","doi":"10.32917/h2020086","DOIUrl":"https://doi.org/10.32917/h2020086","url":null,"abstract":"A bstract . In this paper, we study two eigenvalue problems of the weighted Laplacian and get the Reilly-type bounds and isoperimetric type bounds for the first nonzero n eigenvalues on hypersurfaces of the Euclidean space. Besides, we give lower bounds for the first eigenvalue of weighted p -Laplacian on submanifolds with locally bounded weighted mean curvature. Meanwhile, several applications of these estimates have also been given.","PeriodicalId":55054,"journal":{"name":"Hiroshima Mathematical Journal","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46068206","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}
引用次数: 4
Three dimensional contact metric manifolds with Cotton solitons 具有Cotton孤子的三维接触度量流形
IF 0.2 4区 数学
Hiroshima Mathematical Journal Pub Date : 2021-11-01 DOI: 10.32917/h2020064
Xiaomin Chen
{"title":"Three dimensional contact metric manifolds with Cotton solitons","authors":"Xiaomin Chen","doi":"10.32917/h2020064","DOIUrl":"https://doi.org/10.32917/h2020064","url":null,"abstract":"In this article we study a three dimensional contact metric manifold M 3 with Cotton solitons. We mainly consider two classes of contact metric manifolds admitting Cotton solitons. Firstly, we study a contact metric manifold with Qx 1⁄4 rx, where r is a smooth function on M constant along Reeb vector field x and prove that it is Sasakian or has constant sectional curvature 0 or 1 if the potential vector field of Cotton soliton is collinear with x or is a gradient vector field. Moreover, if r is constant we prove that such a contact metric manifold is Sasakian, flat or locally isometric to one of the following Lie groups: SUð2Þ or SOð3Þ if it admits a Cotton soliton with the potential vector field being orthogonal to Reeb vector field x. Secondly, it is proved that a ðk; m; nÞ-contact metric manifold admitting a Cotton soliton with the potential vector field being Reeb vector field is Sasakian. Furthermore, if the potential vector field is a gradient vector field, we prove that M is Sasakian, flat, a contact metric ð0; 4Þ-space or a contact metric ðk; 0Þ-space with k < 1 and k0 0. For the potential vector field being orthogonal to x, if n is constant we prove that M is either Sasakian, or a ðk; mÞ-contact metric space.","PeriodicalId":55054,"journal":{"name":"Hiroshima Mathematical Journal","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48106976","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}
引用次数: 1
Locally solvable subnormal and quasinormal subgroups in division rings 除法环上局部可解的次正规和拟正规子群
IF 0.2 4区 数学
Hiroshima Mathematical Journal Pub Date : 2021-11-01 DOI: 10.32917/h2020034
Le QUİ DANH, Huynh Viet Khanh
{"title":"Locally solvable subnormal and quasinormal subgroups in division rings","authors":"Le QUİ DANH, Huynh Viet Khanh","doi":"10.32917/h2020034","DOIUrl":"https://doi.org/10.32917/h2020034","url":null,"abstract":"Let $D$ be a division ring with center $F$, and $G$ a subnormal or quasinormal subgroup of $D^*$. We show that if $G$ is locally solvable, then $G$ is contained in $F$.","PeriodicalId":55054,"journal":{"name":"Hiroshima Mathematical Journal","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82339805","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}
引用次数: 5
Vector fields with big and small volume on the 2-sphere 二球面上大小体积的矢量场
IF 0.2 4区 数学
Hiroshima Mathematical Journal Pub Date : 2021-10-14 DOI: 10.32917/h2022009
R. Albuquerque
{"title":"Vector fields with big and small volume on the 2-sphere","authors":"R. Albuquerque","doi":"10.32917/h2022009","DOIUrl":"https://doi.org/10.32917/h2022009","url":null,"abstract":"We consider the problem of minimal volume vector fields on a given Riemann surface, specialising on the case of $M^star$, that is, the arbitrary radius 2-sphere with two antipodal points removed. We discuss the homology theory of the unit tangent bundle $(T^1M^star,partial T^1M^star)$ in relation with calibrations and a certain minimal volume equation. A particular family $X_{mathrm{m},k},:kinmathbb{N}$, of minimal vector fields on $M^star$ is found in an original fashion. The family has unbounded volume, $lim_kmathrm{vol}({X_{mathrm{m},k}}_{|Omega})=+infty$, on any given open subset $Omega$ of $M^star$ and indeed satisfies the necessary differential equation for minimality. Another vector field $X_ell$ is discovered on a region $Omega_1subsetmathbb{S}^2$, with volume smaller than any other known textit{optimal} vector field restricted to $Omega_1$.","PeriodicalId":55054,"journal":{"name":"Hiroshima Mathematical Journal","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2021-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49108640","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}
引用次数: 0
Assassins and torsion functors II 刺客与扭转函子II
IF 0.2 4区 数学
Hiroshima Mathematical Journal Pub Date : 2021-07-08 DOI: 10.32917/h2020095
F. Rohrer
{"title":"Assassins and torsion functors II","authors":"F. Rohrer","doi":"10.32917/h2020095","DOIUrl":"https://doi.org/10.32917/h2020095","url":null,"abstract":"Fairness and centredness of ideals in commutative rings, i.e., the relations between assassins and weak assassins of a module, its small or large torsion submodule, and the corresponding quotients, are studied. General criteria as well as more specific results about idempotent or nil ideals are given, and several examples are presented.","PeriodicalId":55054,"journal":{"name":"Hiroshima Mathematical Journal","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2021-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43017595","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}
引用次数: 0
CFA modules and the finiteness of coassociated primes of local homology modules CFA模与局部同源模的共缔合素数的有限性
IF 0.2 4区 数学
Hiroshima Mathematical Journal Pub Date : 2021-07-01 DOI: 10.32917/H2020073
N. Tri
{"title":"CFA modules and the finiteness of coassociated primes of local homology modules","authors":"N. Tri","doi":"10.32917/H2020073","DOIUrl":"https://doi.org/10.32917/H2020073","url":null,"abstract":"We introduce the concept CFA modules and their applications in investigation the coassociated primes of local homology modules. The main result of this paper says that if $M$ is a CFA linearly compact $R$-module and $t$ is a non-negative integer such that H i I ( M ) is CFA for all $i < t$, then R / I ⊗ R H t I ( M ) is CFA. Hence, the set $mathrm{Coass}_R$ H t I ( M ) is finite.","PeriodicalId":55054,"journal":{"name":"Hiroshima Mathematical Journal","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2021-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44778026","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}
引用次数: 1
Ridge parameters optimization based on minimizing model selection criterion in multivariate generalized ridge regression 基于最小模型选择准则的多元广义岭回归岭参数优化
IF 0.2 4区 数学
Hiroshima Mathematical Journal Pub Date : 2021-07-01 DOI: 10.32917/H2020104
M. Ohishi
{"title":"Ridge parameters optimization based on minimizing model selection criterion in multivariate generalized ridge regression","authors":"M. Ohishi","doi":"10.32917/H2020104","DOIUrl":"https://doi.org/10.32917/H2020104","url":null,"abstract":"A multivariate generalized ridge (MGR) regression provides a shrinkage estimator of the multivariate linear regression by multiple ridge parameters. Since the ridge parameters which adjust the amount of shrinkage of the estimator are unknown, their optimization is an important task to obtain a better estimator. For the univariate case, a fast algorithm has been proposed for optimizing ridge parameters based on minimizing a model selection criterion (MSC) and the algorithm can be applied to various MSCs. In this paper, we extend this algorithm to MGR regression. We also describe the relationship between the MGR estimator which is not sparse and a multivariate adaptive group Lasso estimator which is sparse, under orthogonal explanatory variables.","PeriodicalId":55054,"journal":{"name":"Hiroshima Mathematical Journal","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2021-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47814894","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}
引用次数: 1
On meromorphic functions sharing three two-point sets CM 关于共享三个两点集CM的亚纯函数
IF 0.2 4区 数学
Hiroshima Mathematical Journal Pub Date : 2021-07-01 DOI: 10.32917/H2020058
M. Shirosaki
{"title":"On meromorphic functions sharing three two-point sets CM","authors":"M. Shirosaki","doi":"10.32917/H2020058","DOIUrl":"https://doi.org/10.32917/H2020058","url":null,"abstract":"We show that if three meromorphic functions share three two-point sets CM, then there exist two of the meromorphic functions such that one of them is a Mobius transform of the other.","PeriodicalId":55054,"journal":{"name":"Hiroshima Mathematical Journal","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2021-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47510559","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}
引用次数: 1
A note on simultaneous approximation on Vitushkin sets 关于Vitushkin集同时逼近的一个注记
IF 0.2 4区 数学
Hiroshima Mathematical Journal Pub Date : 2021-03-01 DOI: 10.32917/H2020009
R. Mortini, R. Rupp
{"title":"A note on simultaneous approximation on Vitushkin\u0000 sets","authors":"R. Mortini, R. Rupp","doi":"10.32917/H2020009","DOIUrl":"https://doi.org/10.32917/H2020009","url":null,"abstract":"Given a planar Jordan domain G with rectifiable boundary, it is well known that smooth functions on the closure of G do not always admit smooth extensions to C. Further conditions on the boundary are necessary to guarantee such extensions. On the other hand, Weierstrass’ approximation theorem yields polynomials converging uniformly to f A CðG;CÞ. In this note we show that for Vitushkin sets K with K 1⁄4 K it is always possible to uniformly approximate on K the smooth function f A C ðK ;CÞ by smooth functions fn in C so that also qfn converges uniformly to qf on K. As a byproduct we deduce from its ‘‘smooth in a neighborhood version’’ the general Gauss integral theorem for functions whose partial derivatives in G merely admit continuous extensions to its boundary.","PeriodicalId":55054,"journal":{"name":"Hiroshima Mathematical Journal","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2021-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45254757","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}
引用次数: 0
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