Results in Mathematics最新文献

{"title":"Continuous Operators from Spaces of Lipschitz Functions.","authors":"Christian Bargetz, Jerzy Kąkol, Damian Sobota","doi":"10.1007/s00025-024-02323-z","DOIUrl":"10.1007/s00025-024-02323-z","url":null,"abstract":"<p><p>We study the existence of continuous (linear) operators from the Banach spaces <math> <mrow> <msub><mrow><mspace></mspace> <mtext>Lip</mtext> <mspace></mspace></mrow> <mn>0</mn></msub> <mrow><mo>(</mo> <mi>M</mi> <mo>)</mo></mrow> </mrow> </math> of Lipschitz functions on infinite metric spaces <i>M</i> vanishing at a distinguished point and from their predual spaces <math><mrow><mi>F</mi> <mo>(</mo> <mi>M</mi> <mo>)</mo></mrow> </math> onto certain Banach spaces, including <i>C</i>(<i>K</i>)-spaces and the spaces <math><msub><mi>c</mi> <mn>0</mn></msub> </math> and <math><msub><mi>ℓ</mi> <mn>1</mn></msub> </math> . For pairs of spaces <math> <mrow> <msub><mrow><mspace></mspace> <mtext>Lip</mtext> <mspace></mspace></mrow> <mn>0</mn></msub> <mrow><mo>(</mo> <mi>M</mi> <mo>)</mo></mrow> </mrow> </math> and <i>C</i>(<i>K</i>) we prove that if they are endowed with topologies weaker than the norm topology, then usually no continuous (linear or not) surjection exists between those spaces. It is also showed that if a metric space <i>M</i> contains a bilipschitz copy of the unit sphere <math><msub><mi>S</mi> <msub><mi>c</mi> <mn>0</mn></msub> </msub> </math> of the space <math><msub><mi>c</mi> <mn>0</mn></msub> </math> , then <math> <mrow> <msub><mrow><mspace></mspace> <mtext>Lip</mtext> <mspace></mspace></mrow> <mn>0</mn></msub> <mrow><mo>(</mo> <mi>M</mi> <mo>)</mo></mrow> </mrow> </math> admits a continuous operator onto <math><msub><mi>ℓ</mi> <mn>1</mn></msub> </math> and hence onto <math><msub><mi>c</mi> <mn>0</mn></msub> </math> . Using this, we provide several conditions for a space <i>M</i> implying that <math> <mrow> <msub><mrow><mspace></mspace> <mtext>Lip</mtext> <mspace></mspace></mrow> <mn>0</mn></msub> <mrow><mo>(</mo> <mi>M</mi> <mo>)</mo></mrow> </mrow> </math> is not a Grothendieck space. Finally, we obtain a new characterization of the Schur property for Lipschitz-free spaces: a space <math><mrow><mi>F</mi> <mo>(</mo> <mi>M</mi> <mo>)</mo></mrow> </math> has the Schur property if and only if for every complete discrete metric space <i>N</i> with cardinality <i>d</i>(<i>M</i>) the spaces <math><mrow><mi>F</mi> <mo>(</mo> <mi>M</mi> <mo>)</mo></mrow> </math> and <math><mrow><mi>F</mi> <mo>(</mo> <mi>N</mi> <mo>)</mo></mrow> </math> are weakly sequentially homeomorphic.</p>","PeriodicalId":54490,"journal":{"name":"Results in Mathematics","volume":"80 1","pages":"5"},"PeriodicalIF":1.1,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11611977/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142781571","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Formulas for Bernoulli Numbers and Polynomials","authors":"Ulrich Abel, Horst Alzer","doi":"10.1007/s00025-024-02273-6","DOIUrl":"https://doi.org/10.1007/s00025-024-02273-6","url":null,"abstract":"<p>We present several formulas involving the classical Bernoulli numbers and polynomials. Among others, we extend an identity for Bernoulli polynomials published by Wu et al. (Fibonacci Quart 42:295-299, 2004).</p>","PeriodicalId":54490,"journal":{"name":"Results in Mathematics","volume":"7 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267877","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"On Sums of Sums Involving the Von Mangoldt Function","authors":"Isao Kiuchi, Wataru Takeda","doi":"10.1007/s00025-024-02276-3","DOIUrl":"https://doi.org/10.1007/s00025-024-02276-3","url":null,"abstract":"<p>Let <span>(Lambda )</span> denote the von Mangoldt function, and (<i>n</i>, <i>q</i>) be the greatest common divisor of positive integers <i>n</i> and <i>q</i>. For any positive real numbers <i>x</i> and <i>y</i>, we shall consider several asymptotic formulas for sums of sums involving the von Mangoldt function; <span>( S_{k}(x,y):=sum _{nle y}left( sum _{qle x}right. left. sum _{d|(n,q)}dLambda left( frac{q}{d}right) right) ^{k} )</span> for <span>(k=1,2)</span>.</p>","PeriodicalId":54490,"journal":{"name":"Results in Mathematics","volume":"104 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267878","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Half-Dimensional Immersions into the Para-Complex Projective Space and Ruh–Vilms Type Theorems","authors":"Josef F. Dorfmeister, Roland Hildebrand, Shimpei Kobayashi","doi":"10.1007/s00025-024-02271-8","DOIUrl":"https://doi.org/10.1007/s00025-024-02271-8","url":null,"abstract":"<p>In this paper we study isometric immersions <span>(f:M^n rightarrow {mathbb {C}^{prime }}!P^n )</span> of an <i>n</i>-dimensional pseudo-Riemannian manifold <span>(M^n)</span> into the <i>n</i>-dimensional para-complex projective space <span>({mathbb {C}^{prime }}!P^n )</span>. We study the immersion <i>f</i> by means of a lift <span>(mathfrak {f})</span> of <i>f</i> into a quadric hypersurface in <span>(S^{2n+1}_{n+1})</span>. We find the frame equations and compatibility conditions. We specialize these results to dimension <span>(n = 2)</span> and a definite metric on <span>(M^2)</span> in isothermal coordinates and consider the special cases of Lagrangian surface immersions and minimal surface immersions. We characterize surface immersions with special properties in terms of primitive harmonicity of the Gauss maps.\u0000</p>","PeriodicalId":54490,"journal":{"name":"Results in Mathematics","volume":"25 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142194339","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Growth Order of the Optimal Constants in Turán-Erőd Type Inequalities in $$L^q(K,mu )$$","authors":"Polina Yu. Glazyrina, Yuliya S. Goryacheva, Szilárd Gy. Révész","doi":"10.1007/s00025-024-02225-0","DOIUrl":"https://doi.org/10.1007/s00025-024-02225-0","url":null,"abstract":"<p>In 1939 Turán raised the question about lower estimations of the maximum norm of the derivatives of a polynomial <i>p</i> of maximum norm 1 on the compact set <i>K</i> of the complex plain under the normalization condition that the zeroes of <i>p</i> in question all lie in <i>K</i>. Turán studied the problem for the interval <i>I</i> and the unit disk <i>D</i> and found that with <span>(n:= deg p)</span> tending to infinity, the precise growth order of the minimal possible derivative norm (oscillation order) is <span>(sqrt{n})</span> for <i>I</i> and <i>n</i> for <i>D</i>. Erőd continued the work of Turán considering other domains. Finally, in 2006, Halász and Révész proved that the growth of the minimal possible maximal norm of the derivative is of order <i>n</i> for all compact convex domains. Although Turán himself gave comments about the above oscillation question in <span>(L^q)</span>norms, till recently results were known only for <i>D</i> and <i>I</i>. Recently, we have found order <i>n</i> lower estimations for several general classes of compact convex domains, and proved that in <span>(L^q)</span> norm the oscillation order is at least <span>(n/log n)</span> for all compact convex domains. In the present paper we prove that the oscillation order is not greater than <i>n</i> for all compact (not necessarily convex) domains <i>K</i> and <span>(L^q)</span>norm with respect to any measure supported on more than two points on <i>K</i>.</p>","PeriodicalId":54490,"journal":{"name":"Results in Mathematics","volume":"14 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142194341","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dynamics of Weighted Backward Shifts on Certain Analytic Function Spaces","authors":"Bibhash Kumar Das, Aneesh Mundayadan","doi":"10.1007/s00025-024-02279-0","DOIUrl":"https://doi.org/10.1007/s00025-024-02279-0","url":null,"abstract":"<p>We introduce the Banach spaces <span>(ell ^p_{a,b})</span> and <span>(c_{0,a,b})</span>, of analytic functions on the unit disc, having normalized Schauder bases consisting of polynomials of the form <span>(f_n(z)=(a_n+b_nz)z^n, ~~nge 0)</span>, where <span>({f_n})</span> is assumed to be equivalent to the standard basis in <span>(ell ^p)</span> and <span>(c_0)</span>, respectively. We study the weighted backward shift operator <span>(B_w)</span> on these spaces, and obtain necessary and sufficient conditions for <span>(B_w)</span> to be bounded, and prove that, under some mild assumptions on <span>({a_n})</span> and <span>({b_n})</span>, the operator <span>(B_w)</span> is similar to a compact perturbation of a weighted backward shift on the sequence spaces <span>(ell ^p)</span> or <span>(c_0)</span>. Further, we study the hypercyclicity, mixing, and chaos of <span>(B_w)</span>, and establish the existence of hypercyclic subspaces for <span>(B_w)</span> by computing its essential spectrum. Similar results are obtained for a function of <span>(B_w)</span> on <span>(ell ^p_{a,b})</span> and <span>(c_{0,a,b})</span>.</p>","PeriodicalId":54490,"journal":{"name":"Results in Mathematics","volume":"28 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142194343","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Lower and Upper Bounds for the Generalized Csiszár f-divergence Operator Mapping","authors":"Silvestru Sever Dragomir, Ismail Nikoufar","doi":"10.1007/s00025-024-02266-5","DOIUrl":"https://doi.org/10.1007/s00025-024-02266-5","url":null,"abstract":"<p>Let <span>({textbf{A}}={A_{1},...,A_{n}})</span> and <span>({textbf{B}}={B_{1},...,B_{n}})</span> be two finite sequences of strictly positive operators on a Hilbert space <span>( {mathcal {H}})</span> and <i>f</i>, <span>(h:{mathbb {I}}rightarrow {mathbb {R}})</span> continuous functions with <span>(h&gt;0)</span>.. We consider the generalized Csiszár <i>f</i>-divergence operator mapping defined by </p><span>$$begin{aligned} {textbf{I}}_{fDelta h}({textbf{A}},{textbf{B}})=sum _{i=1}^{n}P_{fDelta h}(A_{i},B_{i}), end{aligned}$$</span><p>where </p><span>$$begin{aligned} P_{fDelta h}(A,B):=h(A)^{1/2}f(h(A)^{-1/2}Bh(A)^{-1/2})h(A)^{1/2} end{aligned}$$</span><p>is introduced for every strictly positive operator <i>A</i> and every self-adjoint operator <i>B</i>, where the spectrum of the operators </p><span>$$begin{aligned} A, A^{-1/2}BA^{-1/2}text { and }h(A)^{-1/2}Bh(A)^{-1/2} end{aligned}$$</span><p>are contained in the closed interval <span>({mathbb {I}})</span>. In this paper we obtain some lower and upper bounds for <span>({textbf{I}}_{fDelta h}({textbf{A}},{textbf{B}}))</span> with applications to the geometric operator mean and the relative operator entropy. We verify the information monotonicity for the Csisz ár <i>f</i>-divergence operator mapping and the generalized Csiszár <i>f</i>-divergence operator mapping.</p>","PeriodicalId":54490,"journal":{"name":"Results in Mathematics","volume":"14 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142194342","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"m-symmetric Operators with Elementary Operator Entries","authors":"B. P. Duggal, I. H. Kim","doi":"10.1007/s00025-024-02272-7","DOIUrl":"https://doi.org/10.1007/s00025-024-02272-7","url":null,"abstract":"<p>Given Banach space operators <i>A</i>, <i>B</i>, let <span>(delta _{A,B})</span> denote the generalised derivation <span>(delta (X)=(L_{A}-R_{B})(X)=AX-XB)</span> and <span>(triangle _{A,B})</span> the length two elementary operator <span>(triangle _{A,B}(X)=(I-L_AR_B)(X)=X-AXB)</span>. This note considers the structure of <i>m</i>-symmetric operators <span>(delta ^m_{triangle _{A_1,B_1},triangle _{A_2,B_2}}(I)=(L_{triangle _{A_1,B_1}} - R_{triangle _{A_2,B_2}})^m(I)=0)</span>. It is seen that there exist scalars <span>(lambda _iin sigma _a(B_1))</span>, <span>(1le ile 2)</span>, such that <span>(delta ^m_{lambda _1 A_1,lambda _2 A_2}(I)=0)</span>. Translated to Hilbert space operators <i>A</i> and <i>B</i> this implies that if <span>(delta ^m_{triangle _{A^*,B^*},triangle _{A,B}}(I)=0)</span>, then there exists <span>({overline{lambda }}in sigma _a(B^*))</span> such that <span>(delta ^m_{(lambda A)^*,lambda A}(I)=0=delta ^m_{{overline{lambda }}B,lambda B^*}(I))</span>. We prove that the operator <span>(delta ^m_{triangle _{A^*,B^*},triangle _{A,B}})</span> is compact if and only if (i) there exists a real number <span>(alpha )</span> and finite sequnces (i) <span>({a_j}_{j=1}^nsubseteq sigma (A))</span>, <span>({b_j}_{j=1}^nsubseteq sigma (B))</span> such that <span>(a_jb_j=1-alpha )</span>, <span>(1le jle n)</span>; (ii) decompositions <span>(oplus _{j=1}^n {mathcal {H}}_j)</span> and <span>(oplus _{j=1}^n{texttt {H}_J})</span> of <span>({mathcal {H}})</span> such that <span>(oplus _{j=1}^n{(A-a_j I)|_{ H_j}})</span> and <span>(oplus _{j=1}^n{(B-b_j I)|_{texttt {H}_j}})</span> are nilpotent. If <span>(delta ^{m}_{triangle _{A^*,B^*},triangle _{A,B}}(I)=0)</span> implies <span>(delta _{triangle _{A^*,B^*},triangle _{A,B}}(I)=0)</span>, then <i>A</i> and <i>B</i> satisfy a (Putnam-Fuglede type) commutativity theorem; conversely, a sufficient condition for <span>(delta ^{m}_{triangle _{A^*,B^*},triangle _{A,B}}(I)=0)</span> to imply <span>(delta _{triangle _{A^*,B^*},triangle _{A,B}}(I)=0)</span> is that <span>({lambda }A)</span> and <span>({overline{lambda }}B)</span> satisfy the commutativity property for scalars <span>(overline{lambda} in sigma _a(B^*))</span>. An analogous result is seen to hold for the operators <span>(triangle ^m_{delta _{A^*,B^*},delta _{A,B}})</span> and <span>(triangle ^m_{delta _{A^*,B^*},delta _{A,B}}(I))</span>. Perturbation by commuting nilpotents is considered.</p>","PeriodicalId":54490,"journal":{"name":"Results in Mathematics","volume":"28 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142194373","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Bohr Phenomena for Holomorphic Mappings with Values in Several Complex Variables","authors":"Hidetaka Hamada, Tatsuhiro Honda","doi":"10.1007/s00025-024-02269-2","DOIUrl":"https://doi.org/10.1007/s00025-024-02269-2","url":null,"abstract":"<p>In the first part of this paper, we study several Bohr radii for holomorphic mappings with values in the unit polydisc <span>(mathbb {U}^N)</span> in <span>(mathbb {C}^{N})</span>. In particular, we obtain the new Bohr radius <span>(r_{k,m}^{***})</span> for holomorphic mappings with lacunary series. Further, we show that when <span>(mge 1)</span>, <span>(r_{k,m}^{***})</span> is asymptotically sharp as <span>(Nrightarrow infty )</span>. Note that when <span>(mge 1)</span>, <span>(r_{k,m}^{***})</span> is completely different from the cases with values in the unit disc <span>(mathbb {U})</span> and in the complex Hilbert balls with higher dimensions. In the second part of this paper, we obtain the Bohr type inequality for holomorphic mappings <i>F</i> with values in the unit ball of a JB<span>(^*)</span>-triple which is a generalization of that for holomorphic mappings <i>F</i> with values in the unit ball of a complex Banach space of the form <span>(F(z)=f(z)z)</span>, where <i>f</i> is a <span>(mathbb {C})</span>-valued holomorphic function.</p>","PeriodicalId":54490,"journal":{"name":"Results in Mathematics","volume":"63 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142194374","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Exponential Bases for Parallelepipeds with Frequencies Lying in a Prescribed Lattice","authors":"Dae Gwan Lee, Götz E. Pfander, David Walnut","doi":"10.1007/s00025-024-02267-4","DOIUrl":"https://doi.org/10.1007/s00025-024-02267-4","url":null,"abstract":"<p>The existence of a Fourier basis with frequencies in <span>(mathbb {R}^d)</span> for the space of square integrable functions supported on a given parallelepiped in <span>(mathbb {R}^d)</span>, has been well understood since the 1950s. In a companion paper, we derived necessary and sufficient conditions for a parallelepiped in <span>(mathbb {R}^d)</span> to permit an orthogonal basis of exponentials with frequencies constrained to be a subset of a prescribed lattice in <span>(mathbb {R}^d)</span>, a restriction relevant in many applications. In this paper, we investigate analogous conditions for parallelepipeds that permit a Riesz basis of exponentials with the same constraints on the frequencies. We provide a sufficient condition on the parallelepiped for the Riesz basis case which directly extends one of the necessary and sufficient conditions obtained in the orthogonal basis case. We also provide a sufficient condition which constrains the spectral norm of the matrix generating the parallelepiped, instead of constraining the structure of the matrix.</p>","PeriodicalId":54490,"journal":{"name":"Results in Mathematics","volume":"44 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142194248","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}