{"title":"A structure-preserving reduced-order finite difference approach for a class of semilinear stochastic partial differential equations driven by white noise","authors":"Jiangping Dong , Wei Zhao , Huanrong Li","doi":"10.1016/j.jmaa.2025.129807","DOIUrl":"10.1016/j.jmaa.2025.129807","url":null,"abstract":"<div><div>This paper presents a novel reduced-order finite difference (ROFD) approach that integrates proper orthogonal decomposition (POD) with the finite difference (FD) method to efficiently solve a class of semilinear stochastic partial differential equations (SPDEs) driven by white noise. SPDEs are a class of mathematical models that incorporate random terms or stochastic processes to describe the evolution of systems under uncertainty. SPDEs play a crucial role in modeling real-world phenomena across various fields, including physics, finance, and environmental science, where stochastic process is an inherent component. However, the presence of noise terms and selection of large sample data pose significant challenges for numerical solutions. The proposed ROFD method not only retains the approximation accuracy of the original FD method but also preserves the structural properties of the original semilinear SPDEs. For instance, the mathematical expectation of the numerical solutions under large-sample data satisfies the maximum principle, energy dissipation and so on. A series of numerical experiments have been performed to evaluate the effectiveness of the ROFD method in solving a class of semilinear SPDEs. The numerical results demonstrate that the ROFD method provides highly accurate numerical solutions, exhibits excellent stability and significantly enhances computational efficiency. Due to these advantages, it serves as a highly competitive and practical numerical method for addressing complex SPDEs in real-world applications.</div></div>","PeriodicalId":50147,"journal":{"name":"Journal of Mathematical Analysis and Applications","volume":"552 2","pages":"Article 129807"},"PeriodicalIF":1.2,"publicationDate":"2025-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144322875","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":"A lowest-order divergence-free virtual element method for Navier-Stokes equations with damping on polygonal mesh","authors":"Yanping Chen , Qing Li , Jian Huang , Yu Xiong","doi":"10.1016/j.jmaa.2025.129792","DOIUrl":"10.1016/j.jmaa.2025.129792","url":null,"abstract":"<div><div>This paper focuses on designing a lowest-order divergence-free virtual element method for solving Navier-Stokes equations with a nonlinear damping term on polygonal meshes. The exact divergence-free property of virtual space preserves the mass-conservation of the system. With the application of Helmholtz projection, we provide stability estimates regarding the velocity. An optimal convergence estimate is derived, showing that the error estimate for the velocity in energy norm is pressure-independent. Finally, we perform various numerical simulations to validate the accuracy of our theoretical findings.</div></div>","PeriodicalId":50147,"journal":{"name":"Journal of Mathematical Analysis and Applications","volume":"552 2","pages":"Article 129792"},"PeriodicalIF":1.2,"publicationDate":"2025-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144314468","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":"Symmetry of finite energy solutions to critical p-Laplacian systems in RN","authors":"Min Zhou, Zexin Zhang","doi":"10.1016/j.jmaa.2025.129812","DOIUrl":"10.1016/j.jmaa.2025.129812","url":null,"abstract":"<div><div>In this paper, we are concerned with the symmetry of finite energy solutions <span><math><mo>(</mo><mi>u</mi><mo>,</mo><mi>v</mi><mo>)</mo></math></span> to the following critical <em>p</em>-Laplacian system:<span><span><span><math><mrow><mrow><mo>{</mo><mtable><mtr><mtd><mo>−</mo><msub><mrow><mi>Δ</mi></mrow><mrow><mi>p</mi></mrow></msub><mi>u</mi><mo>=</mo><msup><mrow><mi>v</mi></mrow><mrow><mi>m</mi></mrow></msup><msup><mrow><mi>u</mi></mrow><mrow><mi>r</mi></mrow></msup><mspace></mspace></mtd><mtd><mtext>in</mtext><mspace></mspace><mspace></mspace><msup><mrow><mi>R</mi></mrow><mrow><mi>N</mi></mrow></msup><mo>,</mo></mtd></mtr><mtr><mtd><mo>−</mo><msub><mrow><mi>Δ</mi></mrow><mrow><mi>p</mi></mrow></msub><mi>v</mi><mo>=</mo><msup><mrow><mi>u</mi></mrow><mrow><mi>q</mi></mrow></msup><msup><mrow><mi>v</mi></mrow><mrow><mi>s</mi></mrow></msup><mspace></mspace></mtd><mtd><mtext>in</mtext><mspace></mspace><mspace></mspace><msup><mrow><mi>R</mi></mrow><mrow><mi>N</mi></mrow></msup><mo>,</mo></mtd></mtr><mtr><mtd><mi>u</mi><mo>></mo><mn>0</mn><mo>,</mo><mi>v</mi><mo>></mo><mn>0</mn><mspace></mspace></mtd><mtd><mtext>in</mtext><mspace></mspace><mspace></mspace><msup><mrow><mi>R</mi></mrow><mrow><mi>N</mi></mrow></msup><mo>,</mo></mtd></mtr></mtable></mrow></mrow></math></span></span></span> where <span><math><mn>1</mn><mo><</mo><mi>p</mi><mo><</mo><mi>N</mi><mo>,</mo><mi>N</mi><mo>≥</mo><mn>2</mn></math></span>, <span><math><mi>m</mi><mo>,</mo><mi>q</mi><mo>></mo><mi>max</mi><mo></mo><mrow><mo>{</mo><mn>1</mn><mo>,</mo><mi>p</mi><mo>−</mo><mn>1</mn><mo>}</mo></mrow><mo>,</mo><mspace></mspace><mi>r</mi><mo>,</mo><mi>s</mi><mo>≥</mo><mn>0</mn></math></span> satisfy <span><math><mi>m</mi><mo>−</mo><mi>s</mi><mo>≥</mo><mi>q</mi><mo>−</mo><mi>r</mi><mo>></mo><mo>−</mo><mi>p</mi><mo>+</mo><mn>1</mn></math></span> and <span><math><mi>m</mi><mo>+</mo><mi>r</mi><mo>+</mo><mn>1</mn><mo>=</mo><mi>q</mi><mo>+</mo><mi>s</mi><mo>+</mo><mn>1</mn><mo>=</mo><msup><mrow><mi>p</mi></mrow><mrow><mo>⁎</mo></mrow></msup><mo>:</mo><mo>=</mo><mfrac><mrow><mi>p</mi><mi>N</mi></mrow><mrow><mi>N</mi><mo>−</mo><mi>p</mi></mrow></mfrac></math></span>. Using decay estimates of the solutions at infinity obtained in <span><span>[34, Theorem 1.3]</span></span>, we apply the moving planes method to prove that <em>u</em> and <em>v</em> are both radial and radially decreasing about some point <span><math><msub><mrow><mi>x</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>∈</mo><msup><mrow><mi>R</mi></mrow><mrow><mi>N</mi></mrow></msup></math></span>.</div></div>","PeriodicalId":50147,"journal":{"name":"Journal of Mathematical Analysis and Applications","volume":"552 2","pages":"Article 129812"},"PeriodicalIF":1.2,"publicationDate":"2025-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144308118","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":"Fundamental solutions for parabolic equations and systems: Universal existence, uniqueness, representation","authors":"Pascal Auscher, Khalid Baadi","doi":"10.1016/j.jmaa.2025.129806","DOIUrl":"10.1016/j.jmaa.2025.129806","url":null,"abstract":"<div><div>In this paper, we develop a universal, conceptually simple and systematic method to prove well-posedness to Cauchy problems for weak solutions of parabolic equations with non-smooth, time-dependent, elliptic part having a variational definition. Our classes of weak solutions are taken with minimal assumptions. We prove the existence and uniqueness of a fundamental solution which seems new in this generality: it is shown to always coincide with the associated evolution family for the initial value problem with zero source and it yields representation of all weak solutions. Our strategy is a variational approach avoiding density arguments, a priori regularity of weak solutions or regularization by smooth operators. One of our main tools are embedding results which yield time continuity of our weak solutions going beyond the celebrated Lions regularity theorem and that is addressing a variety of source terms. We illustrate our results with three concrete applications: second order uniformly elliptic part with Dirichlet boundary condition on domains, integro-differential elliptic part, and second order degenerate elliptic part.</div></div>","PeriodicalId":50147,"journal":{"name":"Journal of Mathematical Analysis and Applications","volume":"552 1","pages":"Article 129806"},"PeriodicalIF":1.2,"publicationDate":"2025-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144321438","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":"Automorphisms of subalgebras of bounded analytic functions","authors":"Kanha Behera, Rahul Maurya, P. Muthukumar","doi":"10.1016/j.jmaa.2025.129804","DOIUrl":"10.1016/j.jmaa.2025.129804","url":null,"abstract":"<div><div>Let <span><math><msup><mrow><mi>H</mi></mrow><mrow><mo>∞</mo></mrow></msup></math></span> denote the algebra of all bounded analytic functions on the unit disk. It is well-known that every (algebra) automorphism of <span><math><msup><mrow><mi>H</mi></mrow><mrow><mo>∞</mo></mrow></msup></math></span> is a composition operator induced by disc automorphism. Maurya et al., (J. Math. Anal. Appl. 530: Paper No: 127698, 2024) proved that every automorphism of the subalgebras <span><math><mo>{</mo><mi>f</mi><mo>∈</mo><msup><mrow><mi>H</mi></mrow><mrow><mo>∞</mo></mrow></msup><mo>:</mo><mi>f</mi><mo>(</mo><mn>0</mn><mo>)</mo><mo>=</mo><mn>0</mn><mo>}</mo></math></span> or <span><math><mo>{</mo><mi>f</mi><mo>∈</mo><msup><mrow><mi>H</mi></mrow><mrow><mo>∞</mo></mrow></msup><mo>:</mo><msup><mrow><mi>f</mi></mrow><mrow><mo>′</mo></mrow></msup><mo>(</mo><mn>0</mn><mo>)</mo><mo>=</mo><mn>0</mn><mo>}</mo></math></span> is a composition operator induced by a rotation. In this article, we give very simple proof of their results. As an interesting generalization, for any <span><math><mi>ψ</mi><mo>∈</mo><msup><mrow><mi>H</mi></mrow><mrow><mo>∞</mo></mrow></msup></math></span>, we show that every automorphism of <span><math><mi>ψ</mi><msup><mrow><mi>H</mi></mrow><mrow><mo>∞</mo></mrow></msup></math></span> must be a composition operator and characterize all such composition operators. Using this characterization, we find all automorphism of <span><math><mi>ψ</mi><msup><mrow><mi>H</mi></mrow><mrow><mo>∞</mo></mrow></msup></math></span> for few choices of <em>ψ</em> with various nature depending on its zeros.</div></div>","PeriodicalId":50147,"journal":{"name":"Journal of Mathematical Analysis and Applications","volume":"552 2","pages":"Article 129804"},"PeriodicalIF":1.2,"publicationDate":"2025-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144322873","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":"Maximum principles and consequences for γ-translators in Rn+1 II","authors":"José Torres Santaella","doi":"10.1016/j.jmaa.2025.129809","DOIUrl":"10.1016/j.jmaa.2025.129809","url":null,"abstract":"<div><div>This paper focuses on the translating solitons of fully nonlinear extrinsic curvature geometric flows in <span><math><msup><mrow><mi>R</mi></mrow><mrow><mi>n</mi><mo>+</mo><mn>1</mn></mrow></msup></math></span>. We present a generalization of the Spruck-Xiao's and Spruck-Sun's convexity results for 1-homogeneous convex/concave curvature functions, and further provide several characterizations of the family of Grim Reaper cylinders under curvature constraints.</div></div>","PeriodicalId":50147,"journal":{"name":"Journal of Mathematical Analysis and Applications","volume":"552 2","pages":"Article 129809"},"PeriodicalIF":1.2,"publicationDate":"2025-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144321115","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 the algebraic lower bound for the radius of spatial analyticity for the Zakharov-Kuznetsov and modified Zakharov-Kuznetsov equations","authors":"Mikaela Baldasso, Mahendra Panthee","doi":"10.1016/j.jmaa.2025.129802","DOIUrl":"10.1016/j.jmaa.2025.129802","url":null,"abstract":"<div><div>We consider the initial value problem (IVP) for the 2D generalized Zakharov-Kuznetsov (ZK) equation<span><span><span><math><mrow><mrow><mo>{</mo><mtable><mtr><mtd><msub><mrow><mo>∂</mo></mrow><mrow><mi>t</mi></mrow></msub><mi>u</mi><mo>+</mo><msub><mrow><mo>∂</mo></mrow><mrow><mi>x</mi></mrow></msub><mi>Δ</mi><mi>u</mi><mo>+</mo><mi>μ</mi><msub><mrow><mo>∂</mo></mrow><mrow><mi>x</mi></mrow></msub><msup><mrow><mi>u</mi></mrow><mrow><mi>k</mi><mo>+</mo><mn>1</mn></mrow></msup><mo>=</mo><mn>0</mn><mo>,</mo><mspace></mspace></mtd><mtd><mo>(</mo><mi>x</mi><mo>,</mo><mi>y</mi><mo>)</mo><mo>∈</mo><msup><mrow><mi>R</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>,</mo><mspace></mspace><mi>t</mi><mo>∈</mo><mi>R</mi><mo>,</mo></mtd></mtr><mtr><mtd><mi>u</mi><mo>(</mo><mi>x</mi><mo>,</mo><mi>y</mi><mo>,</mo><mn>0</mn><mo>)</mo><mo>=</mo><msub><mrow><mi>u</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>(</mo><mi>x</mi><mo>,</mo><mi>y</mi><mo>)</mo><mo>,</mo></mtd></mtr></mtable></mrow></mrow></math></span></span></span> where <span><math><mi>Δ</mi><mo>=</mo><msubsup><mrow><mo>∂</mo></mrow><mrow><mi>x</mi></mrow><mrow><mn>2</mn></mrow></msubsup><mo>+</mo><msubsup><mrow><mo>∂</mo></mrow><mrow><mi>y</mi></mrow><mrow><mn>2</mn></mrow></msubsup></math></span>, <span><math><mi>μ</mi><mo>=</mo><mo>±</mo><mn>1</mn></math></span>, <span><math><mi>k</mi><mo>=</mo><mn>1</mn><mo>,</mo><mn>2</mn></math></span> and the initial data <span><math><msub><mrow><mi>u</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span> is real analytic in a complex strip in <span><math><msup><mrow><mi>C</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span> and have radius of spatial analyticity <span><math><msub><mrow><mi>σ</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span>. For both <span><math><mi>k</mi><mo>=</mo><mn>1</mn></math></span> and <span><math><mi>k</mi><mo>=</mo><mn>2</mn></math></span>, considering a symmetrized version, we prove that there exists <span><math><msub><mrow><mi>T</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>></mo><mn>0</mn></math></span> such that the radius of spatial analyticity of the solution remains the same in the time interval <span><math><mo>[</mo><mo>−</mo><msub><mrow><mi>T</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>,</mo><msub><mrow><mi>T</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>]</mo></math></span>. We also consider the evolution of the radius of spatial analyticity when the local solution extends globally in time. For the Zakharov-Kuznetsov equation (<span><math><mi>k</mi><mo>=</mo><mn>1</mn></math></span>), we prove that, in both focusing (<span><math><mi>μ</mi><mo>=</mo><mn>1</mn></math></span>) and defocusing (<span><math><mi>μ</mi><mo>=</mo><mo>−</mo><mn>1</mn></math></span>) cases, and for any <span><math><mi>T</mi><mo>></mo><msub><mrow><mi>T</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span>, the radius of analyticity cannot decay faster than <span><math><mi>c</mi><msup><mrow><mi>T</mi></mrow><mrow><mo>−</mo><mo>(</mo>","PeriodicalId":50147,"journal":{"name":"Journal of Mathematical Analysis and Applications","volume":"552 2","pages":"Article 129802"},"PeriodicalIF":1.2,"publicationDate":"2025-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144471156","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":"Local and global bifurcation analysis of density-suppressed motility model","authors":"Di Liu , Junping Shi , Weihua Jiang","doi":"10.1016/j.jmaa.2025.129810","DOIUrl":"10.1016/j.jmaa.2025.129810","url":null,"abstract":"<div><div>In this paper, we study a density-suppressed motility reaction-diffusion population model with Dirichlet boundary conditions in spatially heterogeneous environments. We establish the existence of local-in-time classical solutions and apply local bifurcation theory to identify a positive bifurcation point for steady-state solutions. The existence of non-constant positive steady-state solutions is obtained, and it is shown that the bifurcation direction of the bifurcation curve can be either forward or backward, which is determined by the density-suppressed diffusion term. Furthermore, the boundedness of non-constant positive steady-state solutions is obtained by the comparison principle, and the boundedness of solutions implies that the bifurcation branches from local bifurcation can be extended globally, hence a global bifurcation diagram is derived rigorously. Finally, numerical simulations verify our theoretical results and demonstrate the effect of spatial heterogeneity on pattern formation.</div></div>","PeriodicalId":50147,"journal":{"name":"Journal of Mathematical Analysis and Applications","volume":"552 2","pages":"Article 129810"},"PeriodicalIF":1.2,"publicationDate":"2025-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144322874","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}
Robert E. Gaunt , Saralees Nadarajah , Tibor K. Pogány
{"title":"Infinite divisibility of the product of two correlated normal random variables and exact distribution of the sample mean","authors":"Robert E. Gaunt , Saralees Nadarajah , Tibor K. Pogány","doi":"10.1016/j.jmaa.2025.129800","DOIUrl":"10.1016/j.jmaa.2025.129800","url":null,"abstract":"<div><div>We prove that the distribution of the product of two correlated normal random variables with arbitrary means and arbitrary variances is infinitely divisible. We also obtain exact formulas for the probability density function of the sum of independent copies of such random variables.</div></div>","PeriodicalId":50147,"journal":{"name":"Journal of Mathematical Analysis and Applications","volume":"552 2","pages":"Article 129800"},"PeriodicalIF":1.2,"publicationDate":"2025-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144314358","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":"Fractal representations of the number zero on the parabola curve","authors":"Xuemin Wang , Yi Lu , Jingjing Chen , Kan Jiang","doi":"10.1016/j.jmaa.2025.129801","DOIUrl":"10.1016/j.jmaa.2025.129801","url":null,"abstract":"<div><div>Motivated by several results in the study of unique <em>q</em>-expansions, this paper investigates the following problem. Let <span><math><mi>K</mi><mo>⊂</mo><msup><mrow><mi>R</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span> be a self-similar set with the convex hull <span><math><msup><mrow><mo>[</mo><mn>0</mn><mo>,</mo><mn>1</mn><mo>]</mo></mrow><mrow><mn>2</mn></mrow></msup></math></span>. How many distinct pairs <span><math><mo>(</mo><mi>x</mi><mo>,</mo><mi>y</mi><mo>)</mo><mo>∈</mo><mi>K</mi></math></span> satisfy the equation<span><span><span><math><mn>0</mn><mo>=</mo><mi>y</mi><mo>−</mo><msup><mrow><mi>x</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>?</mo></math></span></span></span> We establish the following result:</div><div>For any <span><math><mi>α</mi><mo>∈</mo><mo>(</mo><mn>0</mn><mo>,</mo><mn>2</mn><mo>)</mo></math></span> and any <span><math><mi>ϵ</mi><mo>></mo><mn>0</mn></math></span>, there exists a homogeneous self-similar set <em>K</em> (with convex hull <span><math><msup><mrow><mo>[</mo><mn>0</mn><mo>,</mo><mn>1</mn><mo>]</mo></mrow><mrow><mn>2</mn></mrow></msup></math></span>) such that<span><span><span><math><mi>α</mi><mo>−</mo><mi>ϵ</mi><mo><</mo><msub><mrow><mi>dim</mi></mrow><mrow><mi>H</mi></mrow></msub><mo></mo><mo>(</mo><mi>K</mi><mo>)</mo><mo><</mo><mi>α</mi><mo>,</mo></math></span></span></span> and the equation<span><span><span><math><mn>0</mn><mo>=</mo><mi>y</mi><mo>−</mo><msup><mrow><mi>x</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>,</mo><mspace></mspace><mo>(</mo><mi>x</mi><mo>,</mo><mi>y</mi><mo>)</mo><mo>∈</mo><mi>K</mi><mo>,</mo></math></span></span></span> has exactly countably many distinct solutions. Specifically,<span><span><span><math><mo>{</mo><mo>(</mo><mi>x</mi><mo>,</mo><mi>y</mi><mo>)</mo><mo>:</mo><mi>y</mi><mo>=</mo><msup><mrow><mi>x</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>}</mo><mo>∩</mo><mi>K</mi><mo>=</mo><mrow><mo>{</mo><mrow><mo>(</mo><mfrac><mrow><mn>1</mn></mrow><mrow><msup><mrow><mi>m</mi></mrow><mrow><mi>k</mi></mrow></msup></mrow></mfrac><mo>,</mo><mfrac><mrow><mn>1</mn></mrow><mrow><msup><mrow><mi>m</mi></mrow><mrow><mn>2</mn><mi>k</mi></mrow></msup></mrow></mfrac><mo>)</mo></mrow><mo>:</mo><mi>k</mi><mo>∈</mo><msup><mrow><mi>N</mi></mrow><mrow><mo>+</mo></mrow></msup><mo>∪</mo><mo>{</mo><mn>0</mn><mo>}</mo><mo>}</mo></mrow><mo>∪</mo><mo>{</mo><mo>(</mo><mn>0</mn><mo>,</mo><mn>0</mn><mo>)</mo><mo>}</mo><mo>,</mo></math></span></span></span> where <span><math><msub><mrow><mi>dim</mi></mrow><mrow><mi>H</mi></mrow></msub></math></span> denotes the Hausdorff dimension, and <span><math><mn>1</mn><mo>/</mo><mi>m</mi></math></span>, <span><math><mi>m</mi><mo>∈</mo><msup><mrow><mi>N</mi></mrow><mrow><mo>+</mo></mrow></msup></math></span>, represents the similarity ratio of <em>K</em>. Similar result can be proved for the Bedford-McMullen carpet.</div></div>","PeriodicalId":50147,"journal":{"name":"Journal of Mathematical Analysis and Applications","volume":"552 2","pages":"Article 129801"},"PeriodicalIF":1.2,"publicationDate":"2025-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144314359","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}