{"title":"The Nilpotent Probability of Finite Groups","authors":"Huaquan Wei, Xuanyou Hou, Changman Sun, Xixi Diao, Hui Wu, Liying Yang","doi":"10.1007/s10114-025-2510-5","DOIUrl":"10.1007/s10114-025-2510-5","url":null,"abstract":"<div><p>Let <i>G</i> be a finite group. We denote by <i>ν</i>(<i>G</i>) the probability that two randomly chosen elements of <i>G</i> generate a nilpotent subgroup. In this paper, we characterize the structure of finite groups <i>G</i> with lower bounds <span>({1 over p}, , {{p^{2}+8} over {9p^{2}}})</span> and <span>({p+3} over {4p})</span> on <i>ν</i>(<i>G</i>), where <i>p</i> is a prime divisor of ∣<i>G</i>∣.</p></div>","PeriodicalId":50893,"journal":{"name":"Acta Mathematica Sinica-English Series","volume":"41 4","pages":"1238 - 1246"},"PeriodicalIF":0.8,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143908706","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":"Boundedness of Solutions for a Class of Semilinear Oscillators","authors":"Yan Zhuang, Daxiong Piao, Yanmin Niu","doi":"10.1007/s10114-025-3505-y","DOIUrl":"10.1007/s10114-025-3505-y","url":null,"abstract":"<div><p>We are concerned with the boundedness for the equation <i>x</i>″ + <i>f</i>(<i>x</i>, <i>x</i>′) + <i>ω</i><sup>2</sup><i>x</i> = <i>p</i>(<i>t</i>), where <i>p</i> is quasi-periodic function. Since the corresponding system is non-Hamiltonian, we transform the original system into a new reversible one, the Poincaré mapping of which satisfies the twist theorem for quasi-periodic reversible mappings of low smoothness, or is close to its linear part by normal form theorem. We then obtain results concerning the boundedness of solutions based on the recently work. The above two cases need some smooth and growth assumptions for <i>f</i> and <i>p</i>, which are precisely the innovations of this paper.</p></div>","PeriodicalId":50893,"journal":{"name":"Acta Mathematica Sinica-English Series","volume":"41 4","pages":"1165 - 1180"},"PeriodicalIF":0.8,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143908707","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 a Centro-equiaffine Area-preserving Flow","authors":"Yunlong Yang, Yanlong Zhang","doi":"10.1007/s10114-025-3082-0","DOIUrl":"10.1007/s10114-025-3082-0","url":null,"abstract":"<div><p>This paper will deal with a nonlocal geometric flow in centro-equiaffine geometry, which keeps the enclosed area of the evolving curve and converges smoothly to an ellipse. This model can be viewed as the affine version of Gage’s area-preserving flow in Euclidean geometry.</p></div>","PeriodicalId":50893,"journal":{"name":"Acta Mathematica Sinica-English Series","volume":"41 4","pages":"1091 - 1103"},"PeriodicalIF":0.8,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143908711","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}
Fangfang Wu, Hajo Broersma, Shenggui Zhang, Binlong Li
{"title":"Turán Numbers for Vertex-disjoint Triangles and Pentagons","authors":"Fangfang Wu, Hajo Broersma, Shenggui Zhang, Binlong Li","doi":"10.1007/s10114-025-3272-9","DOIUrl":"10.1007/s10114-025-3272-9","url":null,"abstract":"<div><p>The Turán number, denoted by ex (<i>n</i>, <i>H</i>), is the maximum number of edges of a graph on <i>n</i> vertices containing no graph <i>H</i> as a subgraph. Denote by <i>kC</i><sub><i>ℓ</i></sub> the union of <i>k</i> vertex-disjoint copies of <i>C</i><sub><i>ℓ</i></sub>. In this paper, we present new results for the Turán numbers of vertex-disjoint cycles. Our first results deal with the Turán number of vertex-disjoint triangles ex (<i>n</i>, <i>kC</i><sub>3</sub>). We determine the Turán number ex(<i>n</i>, <i>kC</i><sub>3</sub>) for <span>(n geq {k^{2}+5k over 2})</span> when <i>k</i> ≤ 4, and <i>n</i> ≥ <i>k</i><sup>2</sup> + 2 when <i>k</i> ≥ 4. Moreover, we give lower and upper bounds for ex (<i>n</i>, <i>kC</i><sub>3</sub>) with <span>(3k leq n leq {k^{2}+5k over 2})</span> when <i>k</i> ≤ 4, and 3<i>k</i> ≤ <i>n</i> ≤ <i>k</i><sup>2</sup> + 2 when <i>k</i> ≥ 4. Next, we give a lower bound for the Turán number of vertex-disjoint pentagons ex (<i>n</i>, <i>kC</i><sub>5</sub>). Finally, we determine the Turán number ex (<i>n</i>, <i>kC</i><sub>5</sub>) for <i>n</i> = 5<i>k</i>, and propose two conjectures for ex (<i>n</i>, <i>kC</i><sub>5</sub>) for the other values of <i>n</i>.</p></div>","PeriodicalId":50893,"journal":{"name":"Acta Mathematica Sinica-English Series","volume":"41 4","pages":"1181 - 1195"},"PeriodicalIF":0.8,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143908704","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":"Some Problems about Consonant and Co-Consonant Spaces","authors":"Zhengmao He, Bin Zhao","doi":"10.1007/s10114-025-3080-2","DOIUrl":"10.1007/s10114-025-3080-2","url":null,"abstract":"<div><p>In this paper, we first prove that the retract of a consonant space (or co-consonant space) is consonant (co-consonant). Simultaneously, we consider the co-consonance of two powerspace constructions and proved that (1) the co-consonance of the Smyth powerspace <i>P</i><sub><i>S</i></sub>(<i>X</i>) implies the co-consonance of <i>X</i> if <i>X</i> is strongly compact; (2) the co-consonance of <i>X</i> implies the co-consonance of the Smyth powerspace under some conditions; (3) if the lower powerspace <i>P</i><sub><i>H</i></sub>(<i>X</i>) is co-consonant, then <i>X</i> is co-consonant; (4) for a continuous poset <i>P</i>, the lower powerspace <i>P</i><sub><i>H</i></sub>(Σ<i>P</i>) is co-consonant.</p></div>","PeriodicalId":50893,"journal":{"name":"Acta Mathematica Sinica-English Series","volume":"41 4","pages":"1152 - 1164"},"PeriodicalIF":0.8,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143908708","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":"Positive Solutions for some almost Critical Brezis-Nirenberg Type Problems in Bounded and Exterior Domains","authors":"Salomón Alarcón, Pablo Quijada","doi":"10.1007/s10114-025-3385-1","DOIUrl":"10.1007/s10114-025-3385-1","url":null,"abstract":"<div><p>We study the equation</p><div><div><span>$$-Delta{u}=vert{x}vert^{alpha}u^{p_{alpha}^{ast}+varepsilon}+lambda_{varepsilon}vert{x}vert^{beta}{u}quadtext{in};Omega,$$</span></div></div><p>under the condition <i>u</i> = 0 on ∂Ω, where Ω is a smooth bounded domain in ℝ<sup><i>N</i></sup>, <i>N</i> ≥ 5, which is symmetric respect to <i>x</i><sub>1</sub>, <i>x</i><sub>2</sub>, 2026;, <i>x</i><sub><i>N</i></sub> and contains the origin, <i>α</i> > −2, −2 < <i>β</i> < <i>N</i> − 4, <span>(p_{alpha}^{ast}={N+2alpha+2over{N-2}})</span>, <i>ε</i> > 0 is a small parameter and <i>λ</i><sub><i>ε</i></sub> > 0 depends on <i>ε</i>, with <i>λ</i><sub><i>ε</i></sub> → 0 as <i>ε</i> → 0. Our main focus lies in finding positive solutions that take the form of a tower of bubbles of order <i>α</i>, exhibiting concentration at the origin as <i>ε</i> tends to zero. Furthermore, we extend our study to the equation</p><div><div><span>$$-Delta{u}=vert{x}vert^{alpha}u^{p_{alpha}^{ast}-varepsilon}-lambda_{varepsilon}vert{x}vert^{beta}{u}quadtext{in};mathbb{R}^{N};backslash;B_{1},$$</span></div></div><p>where <i>B</i><sub>1</sub> is the unit ball centered at the origin, under Dirichlet zero boundary condition and an additional vanishing condition at infinity. In this context, we discover positive solutions that take the form of a tower of bubbles of order <i>α</i>, progressively flattening as <i>ε</i> tends to zero.</p></div>","PeriodicalId":50893,"journal":{"name":"Acta Mathematica Sinica-English Series","volume":"41 4","pages":"1131 - 1151"},"PeriodicalIF":0.8,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143908709","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":"Finite Solvable Groups Whose Prime Graphs have Diameter 3","authors":"Guohua Qian","doi":"10.1007/s10114-025-2021-4","DOIUrl":"10.1007/s10114-025-2021-4","url":null,"abstract":"<div><p>Let <i>G</i> be a finite group and <i>π</i>(<i>G</i>) be the set of prime divisors of ∣<i>G</i>∣. The prime graph Γ(<i>G</i>) of <i>G</i> is the graph with vertex set <i>π</i>(<i>G</i>), and different <i>p, q</i> ∈ <i>π</i>(<i>G</i>) are joined by an edge if and only if <i>G</i> has an element of order <i>pq</i>. In this paper, we characterize the finite solvable groups whose prime graphs have diameter 3.</p></div>","PeriodicalId":50893,"journal":{"name":"Acta Mathematica Sinica-English Series","volume":"41 3","pages":"975 - 984"},"PeriodicalIF":0.8,"publicationDate":"2025-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143688319","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":"Preface of the Special Issue on Statistics","authors":"Zhiming Ma, Fuzhou Gong, Liuquan Sun","doi":"10.1007/s10114-025-4551-1","DOIUrl":"10.1007/s10114-025-4551-1","url":null,"abstract":"","PeriodicalId":50893,"journal":{"name":"Acta Mathematica Sinica-English Series","volume":"41 2","pages":"497 - 497"},"PeriodicalIF":0.8,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143455582","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":"Reproducible Learning of Gaussian Graphical Models via Graphical Lasso Multiple Data Splitting","authors":"Kang Hu, Danning Li, Binghui Liu","doi":"10.1007/s10114-025-3324-1","DOIUrl":"10.1007/s10114-025-3324-1","url":null,"abstract":"<div><p>Gaussian graphical models (GGMs) are widely used as intuitive and efficient tools for data analysis in several application domains. To address the reproducibility issue of structure learning of a GGM, it is essential to control the false discovery rate (FDR) of the estimated edge set of the graph in terms of the graphical model. Hence, in recent years, the problem of GGM estimation with FDR control is receiving more and more attention. In this paper, we propose a new GGM estimation method by implementing multiple data splitting. Instead of using the node-by-node regressions to estimate each row of the precision matrix, we suggest directly estimating the entire precision matrix using the graphical Lasso in the multiple data splitting, and our calculation speed is <i>p</i> times faster than the previous. We show that the proposed method can asymptotically control FDR, and the proposed method has significant advantages in computational efficiency. Finally, we demonstrate the usefulness of the proposed method through a real data analysis.</p></div>","PeriodicalId":50893,"journal":{"name":"Acta Mathematica Sinica-English Series","volume":"41 2","pages":"553 - 568"},"PeriodicalIF":0.8,"publicationDate":"2025-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143455417","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":"Variational Bayesian Tensor Quantile Regression","authors":"Yunzhi Jin, Yanqing Zhang","doi":"10.1007/s10114-025-3390-4","DOIUrl":"10.1007/s10114-025-3390-4","url":null,"abstract":"<div><p>Quantile regression is widely used in variable relationship research for statistical learning. Traditional quantile regression model is based on vector-valued covariates and can be efficiently estimated via traditional estimation methods. However, many modern applications involve tensor data with the intrinsic tensor structure. Traditional quantile regression can not deal with tensor regression issues well. To this end, we consider a tensor quantile regression with tensor-valued covariates and develop a novel variational Bayesian estimation approach to make estimation and prediction based on the asymmetric Laplace model and the CANDECOMP/PARAFAC decomposition of tensor coefficients. To incorporate the sparsity of tensor coefficients, we consider the multiway shrinkage priors for marginal factor vectors of tensor coefficients. The key idea of the proposed method is to efficiently combine the prior structural information of tensor and utilize the matricization of tensor decomposition to simplify the complexity of tensor coefficient estimation. The coordinate ascent algorithm is employed to optimize variational lower bound. Simulation studies and a real example show the numerical performances of the proposed method.</p></div>","PeriodicalId":50893,"journal":{"name":"Acta Mathematica Sinica-English Series","volume":"41 2","pages":"733 - 756"},"PeriodicalIF":0.8,"publicationDate":"2025-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143455439","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}