Physica D: Nonlinear Phenomena最新文献_第4页

On the multipeakon system of a two-component Novikov equation 双分量Novikov方程的多峰系统

IF 2.7 3区数学

Physica D: Nonlinear Phenomena Pub Date : 2025-06-19 DOI: 10.1016/j.physd.2025.134781

Xiang-Ke Chang , Jacek Szmigielski

{"title":"On the multipeakon system of a two-component Novikov equation","authors":"Xiang-Ke Chang , Jacek Szmigielski","doi":"10.1016/j.physd.2025.134781","DOIUrl":"10.1016/j.physd.2025.134781","url":null,"abstract":"<div><div>The Novikov equation is a fascinating integrable modification of the Camassa–Holm equation with remarkable properties. This paper concentrates on a two-component Novikov equation featuring a non-self-adjoint 4 × 4 Lax operator. We explore the associated forward and inverse spectral maps, as well as global existence and long-time asymptotics concerning the peakon sector. On one hand, we execute an isospectral deformation to the long-time regime to compute the relevant eigenvalues using a Moser-inspired technique. To achieve this, we first demonstrate the global existence of the peakon flows, then establish a connection between the long-time asymptotics of positions and momenta and the non-zero eigenvalues. We introduce a trio of Weyl functions and show that they are matrix-valued Stieltjes transforms of discrete positive measures, again employing the deformation technique. This effectively linearizes the peakon flows on the spectral data side. Conversely, we tackle the inverse problem using Hermite–Padé approximation techniques that involve tensor products and an added symmetry condition. The thorough analysis guarantees existence and uniqueness, yielding global multipeakon formulas.</div></div>","PeriodicalId":20050,"journal":{"name":"Physica D: Nonlinear Phenomena","volume":"481 ","pages":"Article 134781"},"PeriodicalIF":2.7,"publicationDate":"2025-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144572431","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}

引用次数: 0

Perturbed nonlinear dynamics and decay of sphalerons on circles 圆上闪光点的扰动非线性动力学和衰减

IF 2.7 3区数学

Physica D: Nonlinear Phenomena Pub Date : 2025-06-19 DOI: 10.1016/j.physd.2025.134805

S. Navarro-Obregón , J.M. Queiruga

引用次数: 0

Learning coarse-grained dynamics on graph 在图上学习粗粒度动态

IF 2.7 3区数学

Physica D: Nonlinear Phenomena Pub Date : 2025-06-18 DOI: 10.1016/j.physd.2025.134801

Yin Yu , John Harlim , Daning Huang , Yan Li

引用次数: 0

Study of Poincaré Map and limit cycles for non-smooth Welander’s Ocean Convection Model 非光滑Welander海洋对流模型的poincar<s:1>映射和极限环研究

IF 2.7 3区数学

Physica D: Nonlinear Phenomena Pub Date : 2025-06-17 DOI: 10.1016/j.physd.2025.134780

Yagor Romano Carvalho , Luiz F.S. Gouveia , Richard McGehee

引用次数: 0

The impact of a wind switch on the stability of traveling fronts in a reaction–diffusion model of fire propagation 火传播反应-扩散模型中风转换对行进锋稳定性的影响

IF 2.7 3区数学

Physica D: Nonlinear Phenomena Pub Date : 2025-06-16 DOI: 10.1016/j.physd.2025.134776

Olivia Chandrasekhar , C.K.R.T. Jones , Blake Barker , Rodman Linn

{"title":"The impact of a wind switch on the stability of traveling fronts in a reaction–diffusion model of fire propagation","authors":"Olivia Chandrasekhar , C.K.R.T. Jones , Blake Barker , Rodman Linn","doi":"10.1016/j.physd.2025.134776","DOIUrl":"10.1016/j.physd.2025.134776","url":null,"abstract":"<div><div>For certain values of the wave speed parameter, evolution equations for the temperature of a region of fuel admit traveling wave solutions describing fire fronts. We consider such a system in the form of a nonlinear reaction–diffusion equation with a first-order forcing term capturing the combined effects of ambient and fire-induced wind. The fire-induced wind is introduced by way of a piecewise continuous function that “switches” in space. We demonstrate that, in the case of a spatially dependent wind, traveling wave solutions corresponding to fire fronts exist for a continuum of wave speeds rather than for a single unique speed. Using geometric methods, we determine the range of allowable speeds, refine this range to only those fronts which will persist in nature, and develop a selection mechanism to identify the specific wind configuration corresponding to the most stable solution. For this spectrally preferred front, we find that the wind switch occurs ahead of the fireline in a manner consistent with the physics of air entrainment. Even when the wind is not coupled to the temperature and is instead imposed as an external forcing, the conditions on the existence and stability of front solutions force the wind term in to a configuration reflective of physical reality.</div></div>","PeriodicalId":20050,"journal":{"name":"Physica D: Nonlinear Phenomena","volume":"481 ","pages":"Article 134776"},"PeriodicalIF":2.7,"publicationDate":"2025-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144313504","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}

引用次数: 0

Closed orbits of MHD equilibria with orientation-reversing symmetry 具有方向反转对称的MHD平衡的闭合轨道

IF 2.7 3区数学

Physica D: Nonlinear Phenomena Pub Date : 2025-06-16 DOI: 10.1016/j.physd.2025.134762

David Perrella

引用次数: 0

A study of the reconnection of antiparallel vortices in the infinitely thin case and in the finite thickness case 无限薄和有限厚情况下反平行涡旋重连的研究

IF 2.7 3区数学

Physica D: Nonlinear Phenomena Pub Date : 2025-06-16 DOI: 10.1016/j.physd.2025.134782

Francisco de la Hoz , Sergei Iakunin

{"title":"A study of the reconnection of antiparallel vortices in the infinitely thin case and in the finite thickness case","authors":"Francisco de la Hoz , Sergei Iakunin","doi":"10.1016/j.physd.2025.134782","DOIUrl":"10.1016/j.physd.2025.134782","url":null,"abstract":"<div><div>The reconnection of vortices is an important example of the transition from laminar to turbulent flow. The simplest case is the reconnection of a pair of antiparallel line vortices. At first, they undergo long wave deformation (Crow waves), and then reconnect to form coherent structures. Although the behavior of the vortices before and after the reconnection can be clearly observed, what happens during the reconnection still needs to be explained. In fact, due to the finite thickness of the vortices, it is possible to distinguish different types of reconnection, such as reconnection of vorticity lines or reconnection of isosurfaces of vorticity magnitude. This makes unclear the definition of the reconnection time and reconnection point, which represents one major challenge. Note that the smallest scale of emerged coherent structures also depends on this thickness. In this paper, we consider an infinitely thin vortex approximation to study the vorticity reconnection process. We show that, in this case, the behavior after the reconnection is quasi-periodic, with the quasi-period being independent of the angle between the vortices. We observe a similarity between the behavior of the vortices in the reconnection region and the evolution of a corner of a polygonal vortex under the localized induction approximation, which may be considered as an indicator that the vortices form a corner at the reconnection. At the end, we compare the results with a solution of the Navier–Stokes equations for the reconnection of a pair of antiparallel vortices with finite thickness, where the pressure isosurfaces are used to visualize the reconnection process. We also use the fluid impulse to define the reconnection time, the reconnection point, and the quasi-period for this case.</div></div>","PeriodicalId":20050,"journal":{"name":"Physica D: Nonlinear Phenomena","volume":"481 ","pages":"Article 134782"},"PeriodicalIF":2.7,"publicationDate":"2025-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144335967","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}

引用次数: 0

Stabilized quasi-monotone semi-Lagrangian high-order finite element method for a nonhydrostatic ocean model 非流体静力海洋模型的稳定拟单调半拉格朗日高阶有限元法

IF 2.7 3区数学

Physica D: Nonlinear Phenomena Pub Date : 2025-06-14 DOI: 10.1016/j.physd.2025.134766

João Gabriel Gomes de Oliveira , Pedro Galán del Sastre , Pablo Alcaide Fernández , Jaime Carpio Huertas

{"title":"Stabilized quasi-monotone semi-Lagrangian high-order finite element method for a nonhydrostatic ocean model","authors":"João Gabriel Gomes de Oliveira , Pedro Galán del Sastre , Pablo Alcaide Fernández , Jaime Carpio Huertas","doi":"10.1016/j.physd.2025.134766","DOIUrl":"10.1016/j.physd.2025.134766","url":null,"abstract":"<div><div>We present a high-order finite element method combined with a stabilized quasi-monotone semi-Lagrangian scheme to compute numerical solutions for a nonhydrostatic ocean model. This model is governed by the full incompressible Navier–Stokes equations, coupled with convection–diffusion equations for salinity and temperature, and an equation of state for seawater. Ocean models based on semi-Lagrangian schemes can lead to spurious oscillations near sharp gradients in the solution, often resulting in numerical instabilities and unphysical values such as negative salinity. A novel feature of the proposed method is the use of mesh adaptation strategies to identify elements affected by spurious oscillations, applying the so-called quasi-monotone scheme. The approach is tested on classical two-dimensional convection–diffusion problems, which share governing equations with those used for salinity and temperature conservation, and is validated against published results for stratified oceanic flows. The numerical results demonstrate the effectiveness of the proposed method in achieving high-order accuracy in smooth regions while reducing spurious oscillations near sharp gradients, resulting in stable and accurate numerical solutions for convection–diffusion problems and stratified ocean flows.</div></div>","PeriodicalId":20050,"journal":{"name":"Physica D: Nonlinear Phenomena","volume":"481 ","pages":"Article 134766"},"PeriodicalIF":2.7,"publicationDate":"2025-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144313505","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}

引用次数: 0

Analysis of the autocorrelation function for time series with higher-order temporal correlations: An exponential case 具有高阶时间相关的时间序列的自相关函数分析：一个指数情况

IF 2.7 3区数学

Physica D: Nonlinear Phenomena Pub Date : 2025-06-13 DOI: 10.1016/j.physd.2025.134779

Min-ho Yu, Hang-Hyun Jo

{"title":"Analysis of the autocorrelation function for time series with higher-order temporal correlations: An exponential case","authors":"Min-ho Yu, Hang-Hyun Jo","doi":"10.1016/j.physd.2025.134779","DOIUrl":"10.1016/j.physd.2025.134779","url":null,"abstract":"<div><div>Temporal correlations in the time series observed in various systems have been characterized by the autocorrelation function. Such correlations can be explained by interevent time distributions as well as by correlations between interevent times or higher-order temporal correlations. Despite its importance, the impact of higher-order temporal correlations on the autocorrelation function has been largely unexplored. For studying such impact, we focus on the bursts, i.e., clusters of rapidly occurring events within short time periods, and positive correlations between consecutive burst sizes. We devise a model generating a time series with correlated burst sizes by employing the copula method. We successfully derive the general analytical solution of the autocorrelation function of the model time series for arbitrary distributions of interevent times and burst sizes when consecutive burst sizes are correlated. For the demonstration of our analysis, we adopt exponential distributions of interevent times and burst sizes to find that the analytical solutions are in good agreement with numerical simulations. Our approach helps us to understand how higher-order temporal correlations affect the decaying behavior of the autocorrelation function.</div></div>","PeriodicalId":20050,"journal":{"name":"Physica D: Nonlinear Phenomena","volume":"481 ","pages":"Article 134779"},"PeriodicalIF":2.7,"publicationDate":"2025-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144288949","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}

引用次数: 0

KdV-like soliton gas: similarity and difference in integrable and non-integrable models 类kdv孤子气体：可积与不可积模型的异同

IF 2.7 3区数学

Physica D: Nonlinear Phenomena Pub Date : 2025-06-13 DOI: 10.1016/j.physd.2025.134815

Ekaterina Didenkulova , Marcelo V. Flamarion , Efim Pelinovsky

引用次数: 0