Pub Date : 2024-07-30DOI: 10.1007/s00013-024-02024-7
Alberto Vezzani
We give a quick proof of the fact that the relative de Rham cohomology groups (H^i_{{{,textrm{dR},}}}(X/S)) of a smooth and proper map X/S between schemes over ({mathbb {Q}}) are vector bundles on the base, replacing Hodge-theoretic and transcendental methods with ({mathbb {A}}^1)-homotopy theory.
{"title":"A motivic proof of the finiteness of the relative de Rham cohomology","authors":"Alberto Vezzani","doi":"10.1007/s00013-024-02024-7","DOIUrl":"https://doi.org/10.1007/s00013-024-02024-7","url":null,"abstract":"<p>We give a quick proof of the fact that the relative de Rham cohomology groups <span>(H^i_{{{,textrm{dR},}}}(X/S))</span> of a smooth and proper map <i>X</i>/<i>S</i> between schemes over <span>({mathbb {Q}})</span> are vector bundles on the base, replacing Hodge-theoretic and transcendental methods with <span>({mathbb {A}}^1)</span>-homotopy theory.</p>","PeriodicalId":8346,"journal":{"name":"Archiv der Mathematik","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141867934","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}
Pub Date : 2024-07-20DOI: 10.1007/s00013-024-02033-6
Marc Jornet
We prove a novel, tight lower bound for the norm in (textrm{L}^2[0,T]) of the Caputo fractional derivative. It is based on continuous linear functionals, Peano kernels, and the Gaussian hypergeometric function.
{"title":"A new lower bound for the $$textrm{L}^2$$ -norm of the Caputo fractional derivative","authors":"Marc Jornet","doi":"10.1007/s00013-024-02033-6","DOIUrl":"https://doi.org/10.1007/s00013-024-02033-6","url":null,"abstract":"<p>We prove a novel, tight lower bound for the norm in <span>(textrm{L}^2[0,T])</span> of the Caputo fractional derivative. It is based on continuous linear functionals, Peano kernels, and the Gaussian hypergeometric function.</p>","PeriodicalId":8346,"journal":{"name":"Archiv der Mathematik","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141742240","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}
Pub Date : 2024-07-20DOI: 10.1007/s00013-024-02009-6
Marek Lassak
For a hyperplane H supporting a convex body C in the hyperbolic space (mathbb {H}^d), we define the width of C determined by H as the distance between H and a most distant ultraparallel hyperplane supporting C. The minimum width of C over all supporting H is called the thickness (Delta (C)) of C. A convex body (R subset mathbb {H}^{d}) is said to be reduced if (Delta (Z) < Delta (R)) for every convex body Z properly contained in R. We describe a class of reduced polygons in (mathbb {H}^{2}) and present some properties of them. In particular, we estimate their diameters in terms of their thicknesses.
对于双曲空间 (mathbb {H}^{d})中支持凸体 C 的超平面 H,我们将 H 确定的 C 的宽度定义为 H 与支持 C 的最远超平行超平面之间的距离。我们描述了一类在 (mathbb {H}^{2}) 中的还原多边形,并提出了它们的一些性质。特别是,我们用它们的厚度来估计它们的直径。
{"title":"Reduced polygons in the hyperbolic plane","authors":"Marek Lassak","doi":"10.1007/s00013-024-02009-6","DOIUrl":"https://doi.org/10.1007/s00013-024-02009-6","url":null,"abstract":"<p>For a hyperplane <i>H</i> supporting a convex body <i>C</i> in the hyperbolic space <span>(mathbb {H}^d)</span>, we define the width of <i>C</i> determined by <i>H</i> as the distance between <i>H</i> and a most distant ultraparallel hyperplane supporting <i>C</i>. The minimum width of <i>C</i> over all supporting <i>H</i> is called the thickness <span>(Delta (C))</span> of <i>C</i>. A convex body <span>(R subset mathbb {H}^{d})</span> is said to be reduced if <span>(Delta (Z) < Delta (R))</span> for every convex body <i>Z</i> properly contained in <i>R</i>. We describe a class of reduced polygons in <span>(mathbb {H}^{2})</span> and present some properties of them. In particular, we estimate their diameters in terms of their thicknesses.</p>","PeriodicalId":8346,"journal":{"name":"Archiv der Mathematik","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141742241","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}
Pub Date : 2024-07-20DOI: 10.1007/s00013-024-02031-8
Carlo Alberto De Bernardi, Libor Veselý
Let C be a proper, closed subset with nonempty interior in a normed space X. We define four variants of modulus of convexity for C and prove that they all coincide. This result, which is classical and well-known for (C=B_X) (the unit ball of X), requires a less easy proof than the particular case of (B_X.) We also show that if the modulus of convexity of C is not identically null, then C is bounded. This extends a result by M.V. Balashov and D. Repovš.
我们为 C 定义了四种凸性模的变体,并证明它们都是重合的。对于 (C=B_X)(X 的单位球)来说,这个结果是经典且众所周知的,与 (B_X.)的特殊情况相比,这个结果的证明并不那么容易。 我们还证明了,如果 C 的凸模不等同于空,那么 C 是有界的。这扩展了 M.V. Balashov 和 D. Repovš 的一个结果。
{"title":"Moduli of uniform convexity for convex sets","authors":"Carlo Alberto De Bernardi, Libor Veselý","doi":"10.1007/s00013-024-02031-8","DOIUrl":"https://doi.org/10.1007/s00013-024-02031-8","url":null,"abstract":"<p>Let <i>C</i> be a proper, closed subset with nonempty interior in a normed space <i>X</i>. We define four variants of modulus of convexity for <i>C</i> and prove that they all coincide. This result, which is classical and well-known for <span>(C=B_X)</span> (the unit ball of <i>X</i>), requires a less easy proof than the particular case of <span>(B_X.)</span> We also show that if the modulus of convexity of <i>C</i> is not identically null, then <i>C</i> is bounded. This extends a result by M.V. Balashov and D. Repovš.</p>","PeriodicalId":8346,"journal":{"name":"Archiv der Mathematik","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141742239","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}
Pub Date : 2024-07-18DOI: 10.1007/s00013-024-02029-2
André Carvalho, Jordi Delgado
Building on the work of Brinkmann and Logan, we show that both the Brinkmann problem and the Brinkmann conjugacy problem are decidable for endomorphisms of the free group (mathbb {F}_{n}).
{"title":"Decidability of the Brinkmann problems for endomorphisms of the free group","authors":"André Carvalho, Jordi Delgado","doi":"10.1007/s00013-024-02029-2","DOIUrl":"https://doi.org/10.1007/s00013-024-02029-2","url":null,"abstract":"<p>Building on the work of Brinkmann and Logan, we show that both the Brinkmann problem and the Brinkmann conjugacy problem are decidable for endomorphisms of the free group <span>(mathbb {F}_{n})</span>.</p>","PeriodicalId":8346,"journal":{"name":"Archiv der Mathematik","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141742243","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}
Pub Date : 2024-07-18DOI: 10.1007/s00013-024-02011-y
Giulio Caviglia, Alessandro De Stefani
The purpose of this note is to show that a finitely generated graded module M over (S=k[x_1,ldots ,x_n]), k a field, is sequentially Cohen-Macaulay if and only if its arithmetic degree ({text {adeg}}(M)) agrees with ({text {adeg}}(F/{text {gin}}_textrm{revlex}(U))), where F is a graded free S-module and (M cong F/U). This answers positively a conjecture of Lu and Yu from 2016.
本注释的目的是证明在 k 为域的(S=k[x_1,ldots ,x_n])上有限生成的有级模块 M、当且仅当它的算术度 ({text{adeg}}(M))与 ({text {adeg}}(F/{text {gin}}_textrm{revlex}(U))) 一致时,它才是科恩-麦考莱序列,其中 F 是一个有级自由 S 模块,并且 (M cong F/U).这正面回答了 Lu 和 Yu 在 2016 年提出的猜想。
{"title":"A criterion for sequential Cohen-Macaulayness","authors":"Giulio Caviglia, Alessandro De Stefani","doi":"10.1007/s00013-024-02011-y","DOIUrl":"https://doi.org/10.1007/s00013-024-02011-y","url":null,"abstract":"<p>The purpose of this note is to show that a finitely generated graded module <i>M</i> over <span>(S=k[x_1,ldots ,x_n])</span>, <i>k</i> a field, is sequentially Cohen-Macaulay if and only if its arithmetic degree <span>({text {adeg}}(M))</span> agrees with <span>({text {adeg}}(F/{text {gin}}_textrm{revlex}(U)))</span>, where <i>F</i> is a graded free <i>S</i>-module and <span>(M cong F/U)</span>. This answers positively a conjecture of Lu and Yu from 2016.</p>","PeriodicalId":8346,"journal":{"name":"Archiv der Mathematik","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141742244","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}
Pub Date : 2024-07-18DOI: 10.1007/s00013-024-02028-3
Zhiwei Hao, Lin Wang
In this paper, we give an alternative proof of the main result in Hatano et al. (Tokyo J Math 46(1):125–160, 2023) that the Hardy–Littlewood maximal operator is bounded on the Orlicz–Lorentz space (L^{Phi ,q}({mathbb {R}}^n)) for a Young function (Phi in nabla _2) and (0<q<1.)
本文给出了波多野等人(Tokyo J Math 46(1):125-160,2023)中主要结果的另一种证明,即对于杨函数 (Phi in nabla _2)和 (0<q<1.),哈代-利特尔伍德最大算子在奥利奇-洛伦兹空间 (L^{Phi ,q}({mathbb {R}}^n)) 上是有界的。
{"title":"A remark on the boundedness of the Hardy–Littlewood maximal operator on Orlicz–Lorentz spaces","authors":"Zhiwei Hao, Lin Wang","doi":"10.1007/s00013-024-02028-3","DOIUrl":"https://doi.org/10.1007/s00013-024-02028-3","url":null,"abstract":"<p>In this paper, we give an alternative proof of the main result in Hatano et al. (Tokyo J Math 46(1):125–160, 2023) that the Hardy–Littlewood maximal operator is bounded on the Orlicz–Lorentz space <span>(L^{Phi ,q}({mathbb {R}}^n))</span> for a Young function <span>(Phi in nabla _2)</span> and <span>(0<q<1.)</span></p>","PeriodicalId":8346,"journal":{"name":"Archiv der Mathematik","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141742428","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}
Pub Date : 2024-07-17DOI: 10.1007/s00013-024-02023-8
Nguyen Thi Loan, Pham Truong Xuan
In this paper, we investigate the existence and uniqueness of almost periodic solutions for the parabolic-elliptic Keller–Segel system on the whole space (mathbb {R}^n,, (n geqslant 4)). We work in the framework of critical spaces such as on the weak-Lorentz space (L^{frac{n}{2},infty }(mathbb {R}^n)). Our method is based on the dispersive and smoothing estimates of the heat semigroup and fixed point arguments.
{"title":"Almost periodic solutions of the parabolic-elliptic Keller–Segel system on the whole space","authors":"Nguyen Thi Loan, Pham Truong Xuan","doi":"10.1007/s00013-024-02023-8","DOIUrl":"https://doi.org/10.1007/s00013-024-02023-8","url":null,"abstract":"<p>In this paper, we investigate the existence and uniqueness of almost periodic solutions for the parabolic-elliptic Keller–Segel system on the whole space <span>(mathbb {R}^n,, (n geqslant 4))</span>. We work in the framework of critical spaces such as on the weak-Lorentz space <span>(L^{frac{n}{2},infty }(mathbb {R}^n))</span>. Our method is based on the dispersive and smoothing estimates of the heat semigroup and fixed point arguments.\u0000</p>","PeriodicalId":8346,"journal":{"name":"Archiv der Mathematik","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141742242","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}
Pub Date : 2024-07-16DOI: 10.1007/s00013-024-02025-6
Chiara Nicotera
We consider groups G such that the set ([G,varphi ]={g^{-1}g^{varphi }|gin G}) is a subgroup for every automorphism (varphi ) of G, and we prove that there exists such a group G that is finite and nilpotent of class n for every (nin mathbb N). Then there exists an infinite not nilpotent group with the above property and the Conjecture 18.14 of Khukhro and Mazurov (The Kourovka Notebook No. 20, 2022) is false.
{"title":"On finite groups in which the twisted conjugacy classes of the unit element are subgroups","authors":"Chiara Nicotera","doi":"10.1007/s00013-024-02025-6","DOIUrl":"https://doi.org/10.1007/s00013-024-02025-6","url":null,"abstract":"<p>We consider groups <i>G</i> such that the set <span>([G,varphi ]={g^{-1}g^{varphi }|gin G})</span> is a subgroup for every automorphism <span>(varphi )</span> of <i>G</i>, and we prove that there exists such a group <i>G</i> that is finite and nilpotent of class <i>n</i> for every <span>(nin mathbb N)</span>. Then there exists an infinite not nilpotent group with the above property and the Conjecture 18.14 of Khukhro and Mazurov (The Kourovka Notebook No. 20, 2022) is false.\u0000</p>","PeriodicalId":8346,"journal":{"name":"Archiv der Mathematik","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2024-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141720130","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}
Pub Date : 2024-07-16DOI: 10.1007/s00013-024-02008-7
Raymond Mortini, R. Rupp
{"title":"Sums of infinite series involving the Riemann zeta function","authors":"Raymond Mortini, R. Rupp","doi":"10.1007/s00013-024-02008-7","DOIUrl":"https://doi.org/10.1007/s00013-024-02008-7","url":null,"abstract":"","PeriodicalId":8346,"journal":{"name":"Archiv der Mathematik","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2024-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141642199","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}