Annali dell''Universita di Ferrara最新文献

{"title":"Ultradifferentiable regularity properties of a class of hypoelliptic operators","authors":"Stefan Fürdös","doi":"10.1007/s11565-026-00758-6","DOIUrl":"10.1007/s11565-026-00758-6","url":null,"abstract":"<div><p>We investigate the ultradifferentiable regularity of solutions and vectors of a class of hypoelliptic differential operators first introduced by Hörmander. Our results extend results of Hashimoto–Morimoto–Matsuzawa and Bolley–Camus–Metivier.</p></div>","PeriodicalId":35009,"journal":{"name":"Annali dell''Universita di Ferrara","volume":"72 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11565-026-00758-6.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148986637","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Regularity for a sum of two squares in two variables with symplectic characteristic manifold","authors":"Antonio Bove,&nbsp;Marco Mughetti","doi":"10.1007/s11565-026-00756-8","DOIUrl":"10.1007/s11565-026-00756-8","url":null,"abstract":"<div><p>We study the Gevrey hypoellipticity of the sum of two squares in two variables, satisfying the Hörmander hypothesis: </p><div><div><span>$$ D_{x}^{2} + left( f(x, y) D_{y}right) ^{2} $$</span></div></div><p>assuming that the function <i>f</i>, describing (the space projection of) its characteristic variety, vanishes at <span>(x=0)</span>. A hypoellipticity result is given in a Gevrey class, depending on <i>f</i>. In some examples the found regularity is known to be optimal.</p></div>","PeriodicalId":35009,"journal":{"name":"Annali dell''Universita di Ferrara","volume":"72 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11565-026-00756-8.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148986634","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Brezis-Nirenberg type result for systems on stratified Lie groups","authors":"Annunziata Loiudice,&nbsp;Vikram Yallapa Naik","doi":"10.1007/s11565-026-00755-9","DOIUrl":"10.1007/s11565-026-00755-9","url":null,"abstract":"<div><p>We provide Brezis-Nirenberg type results for subelliptic systems involving sub-Laplacian operators on Carnot groups, extending the results known for the scalar case. Precisely, we investigate existence and non-existence of solutions for critical growth systems with linear perturbations on bounded domains of the considered group.\u0000</p></div>","PeriodicalId":35009,"journal":{"name":"Annali dell''Universita di Ferrara","volume":"72 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11565-026-00755-9.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148986638","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Approximation by Szász–Păltănea Operators using the Appell Polynomials of class (A^2)","authors":"Naokant Deo,&nbsp;Chandra Prakash,&nbsp;D. K. Verma","doi":"10.1007/s11565-026-00748-8","DOIUrl":"10.1007/s11565-026-00748-8","url":null,"abstract":"<div><p>The present article contributes to the new summation-integral form of Szász operators with the help of Appell polynomials of class <span>(A^2)</span>. We first establish the convergence of the proposed operators through Bohman-Korovkin theorem. Subsequently, we investigate the approximation properties in Lipschitz-type space and derive a Voronovskaja-type asymptotic formula, and obtain estimates in terms of modulus of continuity. Lastly, we study the weighted modulus of continuity and establish approximation results for functions whose derivatives are of bounded variation.</p></div>","PeriodicalId":35009,"journal":{"name":"Annali dell''Universita di Ferrara","volume":"72 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148986685","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Top-Degree global solvability for tube complexes in gevrey ultradistributions","authors":"Sandro Coriasco,&nbsp;Alexandre Kirilov,&nbsp;Wagner A. A. de Moraes,&nbsp;Pedro M. Tokoro","doi":"10.1007/s11565-026-00759-5","DOIUrl":"10.1007/s11565-026-00759-5","url":null,"abstract":"<div><p>Let <span>(s&gt;1)</span>, let <span>(M)</span> be a connected, non-compact, oriented real-analytic manifold, and let <span>(omega _1,ldots ,omega _m)</span> be real-valued closed 1-forms of Gevrey order <i>s</i> on <i>M</i>. We study the differential complex naturally associated with this family on <span>(Mtimes mathbb {T}^m)</span>. We prove that its top-degree operator is globally solvable in Roumieu Gevrey ultradistributions, or equivalently that the corresponding top-degree cohomology vanishes. No global hypoellipticity assumption and no arithmetic condition on the periods of the defining forms are required. The proof is carried out in the physical variables and combines fiber translations, a local normal form, and a transport formula along paths in the base manifold. These tools yield propagation of Gevrey regularity, non-confinement of Gevrey singularities, and the support control needed to apply an abstract solvability criterion. The result highlights a sharp contrast with the compact setting, where compatibility conditions are unavoidable and solvability for compatible data may depend on exponential small-denominator conditions.</p></div>","PeriodicalId":35009,"journal":{"name":"Annali dell''Universita di Ferrara","volume":"72 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11565-026-00759-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148986508","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Gradient descent in phase retrieval","authors":"Massimo Cicognani,&nbsp;Alberto Bernardini,&nbsp;Alessandro Ilic Mezza,&nbsp;Roberto Leone Cicognani","doi":"10.1007/s11565-026-00753-x","DOIUrl":"10.1007/s11565-026-00753-x","url":null,"abstract":"<div><p>Alternating projections, like Griffin-Lim and Fast Griffin-Lim algorithms, are among the most widely used iterative methods for phase retrieval. In this paper, we build upon the appendix of the original paper by Griffin and Lim and formulate them as gradient descent algorithms. By this approach, we can give convergence guarantees, evaluate the rate of convergence, and introduce a new phase recovery method based on the Nesterov acceleration of the gradient descent.</p></div>","PeriodicalId":35009,"journal":{"name":"Annali dell''Universita di Ferrara","volume":"72 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11565-026-00753-x.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148986509","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Caputo fractional-order SEIVR modeling and optimal control of the 2026 Bangladesh measles outbreak","authors":"Niraj Pathak,&nbsp;Kunjan Shah,&nbsp;Kamlesh Patel","doi":"10.1007/s11565-026-00754-w","DOIUrl":"10.1007/s11565-026-00754-w","url":null,"abstract":"&lt;div&gt;&lt;p&gt;The 2026 measles outbreak in Bangladesh was officially reported to the World Health Organization (WHO) on 4 April 2026. It constitutes one of the most severe resurgences of vaccine-preventable disease in South Asia in the post-elimination era, with 19,161 suspected cases, 2897 laboratory-confirmed cases, and 166 reported deaths across 58 of 64 districts within 30 days. To capture the memory effect inherent in immunity dynamics and viral persistence, we formulate a fractional-order SEIVR model governed by the Caputo differential operator of order &lt;span&gt;(alpha in (0,1])&lt;/span&gt;. The model incorporates five compartments: Susceptible (&lt;i&gt;S&lt;/i&gt;), Exposed (&lt;i&gt;E&lt;/i&gt;), Infected (&lt;i&gt;I&lt;/i&gt;), Vaccinated (&lt;i&gt;V&lt;/i&gt;), and Recovered (&lt;i&gt;R&lt;/i&gt;) with constant vaccine efficacy &lt;span&gt;(eta =0.85)&lt;/span&gt; reflecting documented one-dose coverage and a vaccine-immunity waning rate &lt;span&gt;(omega )&lt;/span&gt;. Unlike previous theoretical fractional measles models, the proposed framework is calibrated using official WHO surveillance data from the 2026 Bangladesh outbreak, enabling outbreak-specific parameter estimation, quantitative model validation, and evaluation of vaccination strategies under memory-dependent epidemic dynamics. We establish the positivity and boundedness of solutions, derive a closed-form expression for the basic reproduction number &lt;span&gt;(mathcal {R}_{0})&lt;/span&gt; via the next-generation matrix method, and prove local asymptotic stability of the disease-free and endemic equilibria. Global stability conditions are investigated using fractional Lyapunov functionals. Numerical simulations using the Adams-type predictor-corrector scheme are performed over a 365-day horizon and compared against WHO situation-report data. Sensitivity analysis identifies &lt;span&gt;(mathcal {R}_{0})&lt;/span&gt; as most sensitive to the infectious contact rate and the recovery rate. Optimal control theory is applied to minimise the infected population and vaccination cost simultaneously. Results show that, with one-dose efficacy (&lt;span&gt;(eta =0.85)&lt;/span&gt;), vaccination alone cannot drive &lt;span&gt;(mathcal {R}_{0})&lt;/span&gt; below unity; reducing &lt;span&gt;(mathcal {R}_{0}&lt;1)&lt;/span&gt; requires two-dose efficacy (&lt;span&gt;(eta approx 0.97)&lt;/span&gt;) combined with sustained high coverage. Model calibration against the reported WHO outbreak data identified the fractional order &lt;span&gt;(alpha =0.85)&lt;/span&gt; as providing the best agreement with surveillance observations according to the root mean square error (RMSE) criterion. The proposed framework provides outbreak-specific epidemiological insights for vaccination planning and public health decision-making that cannot be obtained from purely theoretical fractional epidemic models lacking real-time outbreak calibration. The principal mathematical contribution is the integration of rigorous fractional stability theory with outbreak-specific parameter estimation and optimal intervention analysis within a unified SEIVR framework. Further, our findings underscor","PeriodicalId":35009,"journal":{"name":"Annali dell''Universita di Ferrara","volume":"72 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148986343","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Integrals of the Wigner distribution on higher dimensional cones","authors":"Nicolas Lerner","doi":"10.1007/s11565-026-00734-0","DOIUrl":"10.1007/s11565-026-00734-0","url":null,"abstract":"<div><p>We study integrals of the Wigner distribution on higher dimensional cones of the phase space. We show in particular that there are very simple examples of cones of the phase space <span>({mathbb {R}}^{2n})</span>, with <span>(nge 2)</span>, on which the integral of the Wigner distribution of a pulse in <span>(L^{2}({mathbb {R}}^{n}))</span> does not converge. It is a sharp contrast with case <span>(n=1)</span>, in which we are able to calculate explicitly the integral of the Wigner distribution on all cones of the phase space <span>({mathbb {R}}^{2})</span>.</p></div>","PeriodicalId":35009,"journal":{"name":"Annali dell''Universita di Ferrara","volume":"72 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148927603","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A study on fractional tumor immune interaction model by the semi-analytic and numerical approach","authors":"Nikita Chaudhary,&nbsp;Twinkle R. Singh,&nbsp;Rajiv K. Singh","doi":"10.1007/s11565-026-00747-9","DOIUrl":"10.1007/s11565-026-00747-9","url":null,"abstract":"<div><p>This work investigates a fractional-order tumor–immune interaction model formulated using the Caputo fractional derivative. Due to the presence of memory and hereditary effects in biological systems, the fractional framework provides a more realistic description of tumor–immune dynamics. The semi-analytical method namely the fractional multi-step differential transform method (FMs-DTM) and the Newton polynomial interpolation based numerical method (NPM) are employed to obtain approximate solutions of the proposed model. A comparative study is carried out to validate the accuracy and reliability of both methods for different fractional orders. Furthermore, the influence of key biological parameters, vaccination strategy, and fractional order on tumor and immune cell populations is analyzed to gain deeper biological insight. Numerical simulations demonstrate close agreement between the proposed methods and existing numerical schemes.</p></div>","PeriodicalId":35009,"journal":{"name":"Annali dell''Universita di Ferrara","volume":"72 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148927136","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"On two new types of Moore subcategories","authors":"M. Gigliarano,&nbsp;P. A. Oliverio","doi":"10.1007/s11565-026-00741-1","DOIUrl":"10.1007/s11565-026-00741-1","url":null,"abstract":"<div><p>We introduce and investigate two new classes of Moore subcategories of the concrete category <span>(textbf{S}[T])</span> associated with an inclusion-preserving endofunctor <span>(T:{textbf {Set}}longrightarrow {textbf {Set}})</span>. We call these kinds of Moore subcategories the <i>nonsingular</i> and the <i>mono</i> Moore <span>((T,{textbf {Set}}))</span>-subcategories, respectively. These notions refine the general theory of <img>-Moore subcategories developed in some recent research and arise naturally when addressing specific problems related to the behavior of monomorphisms. For nonsingular Moore <span>((T,{textbf {Set}}))</span>-subcategories we prove unique transportability and repleteness. Next, we also exhibit explicit descriptions of subobjects and extremal subobjects in terms of the domains of the monomorphisms arising in suitable <span>((text {Epi},text {Mono}))</span>-factorizations in <span>(textbf{S}[T])</span> and a version of the Final Coalgebra Theorem for bounded endofunctors preserving extremal monomorphisms. On the other hand, in the case of mono Moore <span>((T,{textbf {Set}}))</span>-subcategories we show that these subcategories are automatically nonsingular, that the corresponding faithful functor is a Grothendieck <img>-fibration, that embeddings coincide with extremal monomorphisms, and that an extremal subobject classifier exists.</p></div>","PeriodicalId":35009,"journal":{"name":"Annali dell''Universita di Ferrara","volume":"72 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11565-026-00741-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148903447","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}