{"title":"Refining Hölder regularity theory in degenerate drift-diffusion equations","authors":"Tobias Black","doi":"10.1007/s10231-025-01642-4","DOIUrl":"10.1007/s10231-025-01642-4","url":null,"abstract":"<div>\u0000 \u0000 <p>We establish the Hölder continuity of bounded nonnegative weak solutions to </p><div><div><span>$$begin{aligned} big (Phi ^{-1}(w)big )_t=Delta w+nabla cdot big (a(x,t)Phi ^{-1}(w)big )+bbig (x,t,Phi ^{-1}(w)big ), end{aligned}$$</span></div></div><p>with convex <span>(Phi in C^0([0,infty ))cap C^2((0,infty )))</span> satisfying <span>(Phi (0)=0)</span>, <span>(Phi^{prime}>0)</span> on <span>((0,infty ))</span> and </p><div><div><span>$$begin{aligned} sPhi^{primeprime}(s)le CPhi^{prime}(s)quad text {for all }sin [0,s_0] end{aligned}$$</span></div></div><p>for some <span>(C>0)</span> and <span>(s_0in (0,1])</span>. The functions <i>a</i> and <i>b</i> are only assumed to satisfy integrability conditions of the form </p><div><div><span>$$begin{aligned} a&in L^{2q_1}big ((0,T);L^{2q_2}(Omega ;mathbb {R}^N)big ), b&in Mbig (Omega _Ttimes mathbb {R}big ) text {such that }big |b(x,t,xi )big |le {hat{b}}(x,t) text {a.e. for some }{hat{b}}in L^{q_1}big ((0,T);L^{q_2}(Omega )big ) end{aligned}$$</span></div></div><p>with <span>(q_1,q_2>1)</span> such that </p><div><div><span>$$begin{aligned} frac{2}{q_1}+frac{N}{q_2}=2-Nkappa quad text {for some }kappa in (0,tfrac{2}{N}). end{aligned}$$</span></div></div><p>Letting <span>(w=Phi (u))</span> and assuming the inverse <span>(Phi ^{-1}:[0,infty )rightarrow [0,infty ))</span> to be locally Hölder continuous, this entails Hölder regularity for bounded weak solutions of </p><div><div><span>$$begin{aligned} u_t=Delta Phi (u)+nabla cdot big (a(x,t)ubig )+b(x,t,u) end{aligned}$$</span></div></div><p>and, accordingly, covers a wide array of taxis type structures. In particular, many chemotaxis frameworks with nonlinear diffusion, which cannot be covered by the standard literature, fall into this category. After rigorously treating local Hölder regularity, we also extend the regularity result to the associated initial-boundary value problem for boundary conditions of flux-type.</p>\u0000 </div>","PeriodicalId":8265,"journal":{"name":"Annali di Matematica Pura ed Applicata","volume":"205 3","pages":"1397 - 1463"},"PeriodicalIF":0.9,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10231-025-01642-4.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148268637","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":"Kernel estimates for a class of fractional Kolmogorov operators","authors":"Marianna Porfido, Abdelaziz Rhandi, Cristian Tacelli","doi":"10.1007/s10231-025-01653-1","DOIUrl":"10.1007/s10231-025-01653-1","url":null,"abstract":"<div><p>Assuming a weighted Nash type inequality for the generator <span>(-A)</span> of a Markov semigroup, we prove a weighted Nash type inequality for its fractional power and deduce non-uniform bounds on the transition kernel corresponding to the Markov semigroup generated by <span>(-A^alpha )</span>.</p></div>","PeriodicalId":8265,"journal":{"name":"Annali di Matematica Pura ed Applicata","volume":"205 4","pages":"1731 - 1754"},"PeriodicalIF":0.9,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148628679","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":"Positioned and primary positioned (mathcal {C})-semigroups","authors":"C. Cisto, R. Tapia-Ramos","doi":"10.1007/s10231-025-01634-4","DOIUrl":"10.1007/s10231-025-01634-4","url":null,"abstract":"<div><p>Let <span>(mathcal {C})</span> be a positive integer cone and <span>(kin mathcal {C})</span>. A <span>(mathcal {C})</span>-semigroup <i>S</i> is <i>k</i>-positioned if for every <span>(hin mathcal {C}setminus S)</span> we have that <span>(k-h)</span> belongs to <i>S</i>. In this work, we focus on this family of semigroups and introduce primary positioned <span>(mathcal {C})</span>-semigroups, characterizing a subfamily of them through the perspective of irreducibility. Furthermore, we provide some procedures to compute all such semigroups, describing a family of graphs containing all the primary positioned <span>(mathcal {C})</span>-semigroups for a fixed <span>(kin mathcal {C})</span>.</p></div>","PeriodicalId":8265,"journal":{"name":"Annali di Matematica Pura ed Applicata","volume":"205 3","pages":"1123 - 1149"},"PeriodicalIF":0.9,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148268638","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":"Anisotropic lower-dimensional Minkowski content and (mathcal{S}text{-content})","authors":"Filip Fryš","doi":"10.1007/s10231-025-01650-4","DOIUrl":"10.1007/s10231-025-01650-4","url":null,"abstract":"<div>\u0000 \u0000 <p>This paper investigates the lower-dimensional anisotropic Minkowski content and <span>(mathcal {S})</span>-content. We establish that these anisotropic contents exhibit properties analogous to their isotropic counterparts by proving analogous inequalities between the lower-dimensional anisotropic Minkowski content and <span>(mathcal {S})</span>-content <span>(mathcal {S})</span>-content. A key component of our approach is demonstrating that the associated anisotropic volume function is of Kneser type, a result that underpins many of our proofs. In addition, we introduce anisotropic versions of the Minkowski and <span>(mathcal {S})</span>-dimensions and derive inequalities relating them. As an application, we analyze the existence of the <span>(log_2(3))</span>-dimensional anisotropic Minkowski and <span>(mathcal {S})</span>-contents of the Sierpinski gasket.</p>\u0000 </div>","PeriodicalId":8265,"journal":{"name":"Annali di Matematica Pura ed Applicata","volume":"205 3","pages":"1657 - 1683"},"PeriodicalIF":0.9,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10231-025-01650-4.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148268635","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":"Global existence and blow-up phenomena for the periodic problem about a family of Camassa-Holm type equation with both dissipation and dispersion","authors":"Min Zhu, Chen Han, Ying Wang","doi":"10.1007/s10231-025-01647-z","DOIUrl":"10.1007/s10231-025-01647-z","url":null,"abstract":"<div>\u0000 \u0000 <p>We study the periodic problem about a family of Camassa-Holm (CH) type equations incorporating both dissipation and dispersion, which generalizes the b-family equation and the Novikov equation. First, we establish a precise blow-up criterion for strong solutions. Additionally, we prove global existence results for strong solutions by deriving the key conservation inequalities. We employ two distinct analytical approaches to analyze the blow-up phenomena for the periodic problem. Furthermore, we present explicit solutions in the form of single-peakon and multi-peakon solutions.</p>\u0000 </div>","PeriodicalId":8265,"journal":{"name":"Annali di Matematica Pura ed Applicata","volume":"205 3","pages":"1577 - 1613"},"PeriodicalIF":0.9,"publicationDate":"2026-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148268630","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 bielliptic locus in the Hilbert scheme of canonical curves is unirational","authors":"Andrei Stoenică","doi":"10.1007/s10231-025-01643-3","DOIUrl":"10.1007/s10231-025-01643-3","url":null,"abstract":"<div><p>In this paper we prove the unirationality of the locus of bielliptic curves in the Hilbert scheme of canonical curves of genus <span>(g ge 11)</span>. As a consequence, we obtain another proof for the unirationality of the bielliptic locus in the moduli space of curves of genus <span>(g ge 11)</span>.</p></div>","PeriodicalId":8265,"journal":{"name":"Annali di Matematica Pura ed Applicata","volume":"205 3","pages":"1465 - 1477"},"PeriodicalIF":0.9,"publicationDate":"2026-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10231-025-01643-3.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148268742","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":"Intrinsic characterization of projective special complex manifolds","authors":"Vicente Cortés, Kazuyuki Hasegawa","doi":"10.1007/s10231-025-01626-4","DOIUrl":"10.1007/s10231-025-01626-4","url":null,"abstract":"<div><p>We define the notion of an <span>(S^1)</span>-bundle of projective special complex base type and construct a conical special complex manifold from it. Consequently the base space of such an <span>(S^{1})</span>-bundle can be realized as <span>({mathbb {C}}^{*})</span>-quotient of a conical special complex manifold. As a corollary, we give an intrinsic characterization of a projective special complex manifold generalizing Mantegazza’s characterization of a projective special Kähler manifold. Our characterization is in the language of c-projective structures. As an application, a non-trivial <span>(S^1)</span>-family of Obata-Ricci-flat hypercomplex structures (given by a generalization of the rigid c-map) on the tangent bundle of the total space of a <span>({mathbb {C}}^*)</span>-bundle over a complex manifold with certain kind of c-projective structure is constructed. Finally, we show that the quaternionic structure underlying any of these hypercomplex structures is in general not flat and that its flatness implies the vanishing of the c-projective Weyl tensor of the base of the <span>({mathbb {C}}^*)</span>-bundle. Conversely, any c-projectively flat complex manifold satisfying a cohomological integrality condition gives rise to a flat quaternionic structure.</p></div>","PeriodicalId":8265,"journal":{"name":"Annali di Matematica Pura ed Applicata","volume":"205 2","pages":"849 - 901"},"PeriodicalIF":0.9,"publicationDate":"2026-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147828589","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":"Symmetric rank of some reducible quartics","authors":"Liena Colarte-Gómez, Francesco Galuppi","doi":"10.1007/s10231-025-01648-y","DOIUrl":"10.1007/s10231-025-01648-y","url":null,"abstract":"<div><p>In this paper we study the symmetric rank of products of linear forms and an irreducible quadratic form. The main result presents a new, non-trivial lower bound for the rank, and the arguments rely on the apolarity lemma. In the special case of degree 4 we give a list of normal forms for such quartics, and we apply our general result to compute the rank of almost all of them. These families of quartics provide examples of polynomials of generic, supergeneric, and even maximal rank.</p></div>","PeriodicalId":8265,"journal":{"name":"Annali di Matematica Pura ed Applicata","volume":"205 3","pages":"1615 - 1636"},"PeriodicalIF":0.9,"publicationDate":"2026-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10231-025-01648-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148268634","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}
Yingying Guo, Min Li, Yue Liu, Weikui Ye, Zhaoyang Yin
{"title":"Blow up phenomenon and sharp ill-posedness for the short-pulse equation","authors":"Yingying Guo, Min Li, Yue Liu, Weikui Ye, Zhaoyang Yin","doi":"10.1007/s10231-025-01649-x","DOIUrl":"10.1007/s10231-025-01649-x","url":null,"abstract":"<div><p>The <i>short-pulse (SP) equation</i> serves as a fundamental model for describing the propagation of ultra-short optical pulses in silica fibers. In this paper, we rigorously establish the <i>finite-time blow-up phenomenon</i> for a class of large initial data in the Sobolev space <span>(H^{s}(mathbb {R})cap dot{H}^{-1}(mathbb {R}),~s>frac{3}{2}.)</span> In addition, we prove a <i>sharp ill-posedness result</i> for the SP equation with initial data in the critical space <span>(H^{frac{3}{2}}(mathbb {R}).)</span> Combined with the local well-posedness for initial data in <span>(H^{s}(mathbb {R}))</span> with <span>(s>frac{3}{2},)</span> these results provide a complete characterization of the <i>critical Sobolev regularity</i> for the SP equation, yielding a comprehensive understanding of its well-posedness and ill-posedness dynamics.</p></div>","PeriodicalId":8265,"journal":{"name":"Annali di Matematica Pura ed Applicata","volume":"205 3","pages":"1637 - 1655"},"PeriodicalIF":0.9,"publicationDate":"2025-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148268745","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":"Quantitative unique continuation property for fourth-order Baouendi-Grushin type subelliptic operators with a potential","authors":"Yusheng Qiu, Jinggang Tan, Aliang Xia","doi":"10.1007/s10231-025-01645-1","DOIUrl":"10.1007/s10231-025-01645-1","url":null,"abstract":"<div>\u0000 \u0000 <p>We investigate the quantitative unique continuation property for solutions to </p><div><div><span>$$begin{aligned} Delta ^2_{X} u = V u, end{aligned}$$</span></div></div><p>where <span>(Delta _{X} = Delta _{x} + |x|^{2beta } Delta _{y})</span> (<span>(0 < beta le 1)</span>), with <span>(x in mathbb {R}^{m})</span> and <span>(y in mathbb {R}^{n})</span>, denotes a class of subelliptic operators of Baouendi-Grushin type. The potential <i>V</i> is assumed to be bounded and satisfy <span>(|Z V| le K psi )</span> for some constant <span>(K>0)</span>, where <span>(Z= sum _{i=1}^m x_i partial _{x_i} + (beta +1)sum _{j=1}^n y_j partial _{y_j})</span>, <span>(psi )</span> is the angle function given by <span>(psi = frac{|x|^{2beta }}{rho ^{2beta }})</span>, and </p><div><div><span>$$begin{aligned} rho (x,y) = left( |x|^{2(beta +1)} + (beta +1)^2 |y|^2right) ^{frac{1}{2(beta +1)}} end{aligned}$$</span></div></div><p>defines the associated pseudo-gauge. By adapting Almgren’s approach, we establish an almost monotonicity formula for the frequency function. As a consequence, we derive a quantitative unique continuation result for solutions to the fourth-order subelliptic equation.</p>\u0000 </div>","PeriodicalId":8265,"journal":{"name":"Annali di Matematica Pura ed Applicata","volume":"205 3","pages":"1509 - 1539"},"PeriodicalIF":0.9,"publicationDate":"2025-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148268746","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}