{"title":"Gauge transformation for the kinetic derivative nonlinear Schrödinger equation on the torus","authors":"Nobu Kishimoto , Yoshio Tsutsumi","doi":"10.1016/j.jde.2025.113792","DOIUrl":"10.1016/j.jde.2025.113792","url":null,"abstract":"<div><div>We consider the kinetic derivative nonlinear Schrödinger equation, which is a one-dimensional nonlinear Schrödinger equation with a cubic derivative nonlinear term containing the Hilbert transformation. In our previous work, we proved small-data global well-posedness of the Cauchy problem on the torus in Sobolev space <span><math><msup><mrow><mi>H</mi></mrow><mrow><mi>s</mi></mrow></msup></math></span> for <span><math><mi>s</mi><mo>></mo><mn>1</mn><mo>/</mo><mn>2</mn></math></span> by combining the Fourier restriction norm method with the parabolic smoothing effect, which is available in the periodic setting. In this article, we improve the regularity range to <span><math><mi>s</mi><mo>></mo><mn>1</mn><mo>/</mo><mn>4</mn></math></span> for the global well-posedness by constructing an effective gauge transformation. Moreover, we remove the smallness assumption by making use of the dissipative nature of the equation.</div></div>","PeriodicalId":15623,"journal":{"name":"Journal of Differential Equations","volume":"453 ","pages":"Article 113792"},"PeriodicalIF":2.3,"publicationDate":"2025-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145110216","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"On a fractional semilinear Neumann problem arising in Chemotaxis","authors":"Eleonora Cinti, Matteo Talluri","doi":"10.1016/j.jde.2025.113779","DOIUrl":"10.1016/j.jde.2025.113779","url":null,"abstract":"<div><div>We study a semilinear and nonlocal Neumann problem, which is the fractional analogue of the problem considered by Lin–Ni–Takagi in the '80s. The model under consideration arises in the description of stationary configurations of the Keller–Segel model for chemotaxis, when a nonlocal diffusion for the concentration of the chemical is considered. In particular, we extend to any fractional power <span><math><mi>s</mi><mo>∈</mo><mo>(</mo><mn>0</mn><mo>,</mo><mn>1</mn><mo>)</mo></math></span> of the Laplacian (with homogeneous Neumann boundary conditions) the results obtained in <span><span>[23]</span></span> for <span><math><mi>s</mi><mo>=</mo><mn>1</mn><mo>/</mo><mn>2</mn></math></span>. We prove existence and some qualitative properties of non–constant solutions when the diffusion parameter <em>ε</em> is small enough, and on the other hand, we show that for <em>ε</em> large enough any solution must be necessarily constant.</div></div>","PeriodicalId":15623,"journal":{"name":"Journal of Differential Equations","volume":"452 ","pages":"Article 113779"},"PeriodicalIF":2.3,"publicationDate":"2025-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145120559","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Conditional sofic mean dimension","authors":"Bingbing Liang","doi":"10.1016/j.jde.2025.113785","DOIUrl":"10.1016/j.jde.2025.113785","url":null,"abstract":"<div><div>We undertake a study of the conditional mean dimensions for a factor map between continuous actions of a sofic group on two compact metrizable spaces. When the group is infinitely amenable, all these concepts recover as the conditional mean dimensions introduced in <span><span>[31]</span></span>. A range of results established for actions of amenable groups is extended to the sofic framework.</div><div>Additionally, our exploration encompasses the study of the relative mean dimension introduced by Tsukamoto, shedding light on its inherent correlation with the conditional metric mean dimension within the sofic context. A lower bound on the conditional metric mean dimension, originally proposed by Shi-Tsukamoto, is extended to the sofic case.</div></div>","PeriodicalId":15623,"journal":{"name":"Journal of Differential Equations","volume":"452 ","pages":"Article 113785"},"PeriodicalIF":2.3,"publicationDate":"2025-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145120564","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"On computations of Poincaré-Dulac normal forms","authors":"Tatjana Petek , Valery G. Romanovski","doi":"10.1016/j.jde.2025.113781","DOIUrl":"10.1016/j.jde.2025.113781","url":null,"abstract":"<div><div>There are two approaches to computing Poincaré-Dulac normal forms of systems of ODEs. Under the original approach used by Poincaré and Dulac the normalizing transformation is explicitly computed. On each step, the normalizing procedure requires the substitution of a polynomial into a series. Under the other approach, a normal form is computed using Lie transformations. In this case, the changes of coordinates are performed as actions of certain infinitesimal generators. In both cases, on each step the homological equation is solved in the vector space of polynomial vector fields <span><math><msubsup><mrow><mi>V</mi></mrow><mrow><mi>j</mi></mrow><mrow><mi>n</mi></mrow></msubsup></math></span> where each component of the vector field is a homogeneous polynomial of degree <em>j</em>. We present a novel approach which leads to two new algorithms for normal form computations. The first one is designed for polynomial systems of ODEs in which the coefficients of all terms are treated as parameters. While our method employs Lie transformations, the homological equation is solved not in <span><math><msubsup><mrow><mi>V</mi></mrow><mrow><mi>j</mi></mrow><mrow><mi>n</mi></mrow></msubsup></math></span> but in the vector space of polynomial vector fields where each component is a homogeneous polynomial in the parameters of the system. It is shown that the space of the parameters is a kind of dual space and the computation of normal forms can be performed in the space of parameters treated as the space of generalized vector fields, which we call the lattice vector fields. The second algorithm applies to any analytic or formal autonomous system of ODEs and offers one of the simplest normal form computation methods available in the literature. Remarkably, the procedure involves only arithmetic operations with scalars, significantly simplifying the computational process.</div></div>","PeriodicalId":15623,"journal":{"name":"Journal of Differential Equations","volume":"452 ","pages":"Article 113781"},"PeriodicalIF":2.3,"publicationDate":"2025-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145120565","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Smooth Koopman eigenfunctions","authors":"Suddhasattwa Das","doi":"10.1016/j.jde.2025.113786","DOIUrl":"10.1016/j.jde.2025.113786","url":null,"abstract":"<div><div>Any dynamical system, whether it is generated by a differential equation or a transformation map on a manifold, induces a dynamics on functional-spaces. The choice of functional-space may vary, but the induced dynamics is always linear, and codified by the Koopman operator. The eigenfunctions of the Koopman operator are of extreme importance in the study of the dynamics. They provide a clear distinction between the mixing and non-mixing components of the dynamics, and also reveal embedded toral rotations. The usual choice of functional-space is <span><math><msup><mrow><mi>L</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span>, a class of square integrable functions. A fundamental problem with eigenfunctions in <span><math><msup><mrow><mi>L</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span> is that they are often extremely discontinuous, particularly if the system is chaotic. There are some prototypical systems called skew-product dynamics in which <span><math><msup><mrow><mi>L</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span> Koopman eigenfunctions are also smooth. The article shows that under general assumptions on an ergodic system, these prototypical examples are the only possibility. Moreover, the smooth eigenfunctions can be used to create a change of variables which explicitly characterizes the weakly mixing component too.</div></div>","PeriodicalId":15623,"journal":{"name":"Journal of Differential Equations","volume":"453 ","pages":"Article 113786"},"PeriodicalIF":2.3,"publicationDate":"2025-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145110215","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Weak and mild solutions to the MHD equations and the viscoelastic Navier–Stokes equations with damping in Wiener amalgam spaces","authors":"Chen-Chih Lai","doi":"10.1016/j.jde.2025.113777","DOIUrl":"10.1016/j.jde.2025.113777","url":null,"abstract":"<div><div>We study the three-dimensional incompressible magnetohydrodynamic (MHD) equations and the incompressible viscoelastic Navier–Stokes equations with damping. Building on techniques developed by Bradshaw, et al. (2024) <span><span>[1]</span></span>, we prove the existence of mild solutions in Wiener amalgam spaces that satisfy the corresponding spacetime integral bounds. In addition, we construct global-in-time local energy weak solutions in these amalgam spaces using the framework introduced by Bradshaw and Tsai (2021) <span><span>[4]</span></span>. As part of this construction, we also establish several properties of local energy solutions with <span><math><msubsup><mrow><mi>L</mi></mrow><mrow><mi>uloc</mi></mrow><mrow><mn>2</mn></mrow></msubsup></math></span> initial data, including initial and eventual regularity as well as small-large uniqueness, extending analogous results obtained for the Navier–Stokes equations by Bradshaw and Tsai (2020) <span><span>[3]</span></span>.</div></div>","PeriodicalId":15623,"journal":{"name":"Journal of Differential Equations","volume":"452 ","pages":"Article 113777"},"PeriodicalIF":2.3,"publicationDate":"2025-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145108494","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Discrete Lyapunov functional for cyclic systems of differential equations with time-variable or state-dependent delay","authors":"István Balázs , Ábel Garab","doi":"10.1016/j.jde.2025.113768","DOIUrl":"10.1016/j.jde.2025.113768","url":null,"abstract":"<div><div>We consider nonautonomous cyclic systems of delay differential equations with variable delay. Under suitable feedback assumptions, we define an integer-valued Lyapunov functional related to the number of sign changes of the coordinate functions of solutions. We prove that this functional possesses properties analogous to those established by Mallet-Paret and Sell for the constant delay case and by Krisztin and Arino for the scalar case. We also apply the results to equations with state-dependent delays.</div></div>","PeriodicalId":15623,"journal":{"name":"Journal of Differential Equations","volume":"452 ","pages":"Article 113768"},"PeriodicalIF":2.3,"publicationDate":"2025-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145108495","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Thermo-elasticity problems with evolving microstructures","authors":"Michael Eden , Adrian Muntean","doi":"10.1016/j.jde.2025.113764","DOIUrl":"10.1016/j.jde.2025.113764","url":null,"abstract":"<div><div>We consider the mathematical analysis and homogenization of a moving boundary problem posed for a highly heterogeneous, periodically perforated domain. More specifically, we are looking at a one-phase thermo-elasticity system with phase transformations where small inclusions, initially periodically distributed, are growing or shrinking based on a kinetic under-cooling-type law and where surface stresses are created based on the curvature of the phase interface. This growth is assumed to be uniform in each individual cell of the perforated domain. After transforming to the initial reference configuration (utilizing the Hanzawa transformation), we use the contraction mapping principle to show the existence of a unique solution for a possibly small but <em>ε</em> independent time interval (<em>ε</em> is here the scale of heterogeneity).</div><div>In the homogenization limit, we recover a macroscopic thermo-elasticity problem which is strongly non-linearly coupled (via an internal parameter called height function) to local changes in geometry. As a direct by-product of the mathematical analysis work, we present an alternative equivalent formulation which lends itself to an effective pre-computing strategy that is very much needed as the limit problem is computationally expensive.</div></div>","PeriodicalId":15623,"journal":{"name":"Journal of Differential Equations","volume":"452 ","pages":"Article 113764"},"PeriodicalIF":2.3,"publicationDate":"2025-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145108496","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Fine boundary regularity for fully nonlinear mixed local-nonlocal problems","authors":"Mitesh Modasiya, Abhrojyoti Sen","doi":"10.1016/j.jde.2025.113780","DOIUrl":"10.1016/j.jde.2025.113780","url":null,"abstract":"<div><div>We consider Dirichlet problems for fully nonlinear mixed local-nonlocal non-translation invariant operators. For a bounded <span><math><msup><mrow><mi>C</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span> domain <span><math><mi>Ω</mi><mo>⊂</mo><msup><mrow><mi>R</mi></mrow><mrow><mi>d</mi></mrow></msup></math></span>, let <span><math><mi>u</mi><mo>∈</mo><mi>C</mi><mo>(</mo><msup><mrow><mi>R</mi></mrow><mrow><mi>d</mi></mrow></msup><mo>)</mo></math></span> be a viscosity solution of such Dirichlet problem. We obtain global Lipschitz regularity and fine boundary regularity for <em>u</em> by constructing appropriate sub and supersolutions coupled with a <em>Harnack type</em> inequality. We apply these results to obtain Hölder regularity of <em>Du</em> up to the boundary.</div></div>","PeriodicalId":15623,"journal":{"name":"Journal of Differential Equations","volume":"452 ","pages":"Article 113780"},"PeriodicalIF":2.3,"publicationDate":"2025-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145108489","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Travelling wave solutions to a microtube-driven glioma invasion model","authors":"Ryan Thiessen, Thomas Hillen","doi":"10.1016/j.jde.2025.113759","DOIUrl":"10.1016/j.jde.2025.113759","url":null,"abstract":"<div><div>In this article, we establish the existence of travelling wave solutions for a non-cooperative reaction-diffusion model representing glioma cell invasion. The model describes the microtube-driven migration of glioma consisting of an ODE equation describing the dynamics of the tumour bulk and a reaction-diffusion equation for the tumour microtubes. We derive an explicit formula for the minimum wave speed <span><math><mover><mrow><mi>c</mi></mrow><mrow><mo>¯</mo></mrow></mover></math></span> based on system parameters such that travelling waves exist for speeds <span><math><mi>c</mi><mo>≥</mo><mover><mrow><mi>c</mi></mrow><mrow><mo>¯</mo></mrow></mover></math></span> while no travelling wave solution exists for <span><math><mi>c</mi><mo><</mo><mover><mrow><mi>c</mi></mrow><mrow><mo>¯</mo></mrow></mover></math></span>. We prove the existence of travelling wave solutions by constructing upper and lower solutions and employing Schauder's fixed point theorem. We obtain non-existence for small speeds by use of the negative one-sided Laplace transform. Our result is one of the few complete results on travelling waves of a non-cooperative partially degenerate reaction-diffusion systems. The findings have implications for understanding glioma spread dynamics and potential modelling applications in predicting tumour progression based on cellular migration speeds.</div></div>","PeriodicalId":15623,"journal":{"name":"Journal of Differential Equations","volume":"452 ","pages":"Article 113759"},"PeriodicalIF":2.3,"publicationDate":"2025-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145108488","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}