Philipp Dönges, Thomas Götz, Nataliia Kruchinina, Tyll Krüger, Karol Niedzielewski, Viola Priesemann, Moritz Schäfer
SIAM Journal on Applied Mathematics, Volume 84, Issue 4, Page 1460-1481, August 2024. Abstract. Households play an important role in disease dynamics. Many infections happen there due to the close contact, while mitigation measures mainly target the transmission between households. Therefore, one can see households as boosting the transmission depending on household size. To study the effect of household size and size distribution, we differentiated within and between household reproduction rates. There are basically no preventive measures, and thus the close contacts can boost the spread. We explicitly incorporated that typically only a fraction of all household members are infected. Thus, viewing the infection of a household of a given size as a splitting process generating a new small fully infected subhousehold and a remaining still susceptible subhousehold, we derive a compartmental ODE model for the dynamics of the subhouseholds. In this setting, the basic reproduction number as well as prevalence and the peak of an infection wave in a population with given household size distribution can be computed analytically. We compare numerical simulation results of this novel household ODE model with results from an agent-based model using data for realistic household size distributions of different countries. We find good agreement of both models showing the catalytic effect of large households on the overall disease dynamics.
{"title":"SIR Model for Households","authors":"Philipp Dönges, Thomas Götz, Nataliia Kruchinina, Tyll Krüger, Karol Niedzielewski, Viola Priesemann, Moritz Schäfer","doi":"10.1137/23m1556861","DOIUrl":"https://doi.org/10.1137/23m1556861","url":null,"abstract":"SIAM Journal on Applied Mathematics, Volume 84, Issue 4, Page 1460-1481, August 2024. <br/> Abstract. Households play an important role in disease dynamics. Many infections happen there due to the close contact, while mitigation measures mainly target the transmission between households. Therefore, one can see households as boosting the transmission depending on household size. To study the effect of household size and size distribution, we differentiated within and between household reproduction rates. There are basically no preventive measures, and thus the close contacts can boost the spread. We explicitly incorporated that typically only a fraction of all household members are infected. Thus, viewing the infection of a household of a given size as a splitting process generating a new small fully infected subhousehold and a remaining still susceptible subhousehold, we derive a compartmental ODE model for the dynamics of the subhouseholds. In this setting, the basic reproduction number as well as prevalence and the peak of an infection wave in a population with given household size distribution can be computed analytically. We compare numerical simulation results of this novel household ODE model with results from an agent-based model using data for realistic household size distributions of different countries. We find good agreement of both models showing the catalytic effect of large households on the overall disease dynamics.","PeriodicalId":51149,"journal":{"name":"SIAM Journal on Applied Mathematics","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141614588","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
SIAM Journal on Applied Mathematics, Volume 84, Issue 4, Page 1439-1459, August 2024. Abstract. Nonlinear conservation laws such as the system of ideal magnetohydrodynamics (MHD) equations may develop singularities over time. In these situations, viscous regularization is a common approach to regain regularity of the solution. In this paper, we present a new viscous flux to regularize the MHD equations that holds many attractive properties. In particular, we prove that the proposed viscous flux preserves positivity of density and internal energy, satisfies the minimum entropy principle, is consistent with all generalized entropies, and is Galilean and rotationally invariant. We also provide a variation of the viscous flux that conserves angular momentum. To make the analysis more useful for numerical schemes, the divergence of the magnetic field is not assumed to be zero. Using continuous finite elements, we show several numerical experiments, including contact waves and magnetic reconnection.
{"title":"Viscous Regularization of the MHD Equations","authors":"Tuan Anh Dao, Lukas Lundgren, Murtazo Nazarov","doi":"10.1137/23m1564274","DOIUrl":"https://doi.org/10.1137/23m1564274","url":null,"abstract":"SIAM Journal on Applied Mathematics, Volume 84, Issue 4, Page 1439-1459, August 2024. <br/> Abstract. Nonlinear conservation laws such as the system of ideal magnetohydrodynamics (MHD) equations may develop singularities over time. In these situations, viscous regularization is a common approach to regain regularity of the solution. In this paper, we present a new viscous flux to regularize the MHD equations that holds many attractive properties. In particular, we prove that the proposed viscous flux preserves positivity of density and internal energy, satisfies the minimum entropy principle, is consistent with all generalized entropies, and is Galilean and rotationally invariant. We also provide a variation of the viscous flux that conserves angular momentum. To make the analysis more useful for numerical schemes, the divergence of the magnetic field is not assumed to be zero. Using continuous finite elements, we show several numerical experiments, including contact waves and magnetic reconnection.","PeriodicalId":51149,"journal":{"name":"SIAM Journal on Applied Mathematics","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141567912","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
SIAM Journal on Applied Mathematics, Volume 84, Issue 4, Page 1413-1438, August 2024. Abstract. We review a model for a solid electrolyte derived under thermodynamics principles. We nondimensionalize and scale the model to identify small parameters where we identify a scaling that controls the width of the space charge layer in the electrolyte. We present asymptotic analyses and numerical solutions for the one-dimensional zero charge flux equilibrium problem. We introduce an auxiliary variable to remove singularities from the domain in order to facilitate robust numerical simulations. From the asymptotics, we identify three distinct regions: bulk, boundary, and intermediate layers. The boundary and intermediate layers form the space charge layer of the solid electrolyte, which we can further distinguish as strong and weak space charge layers, respectively. The weak space charge layer is characterized by a length, [math], which is equivalent to the Debye length of a standard liquid electrolyte. The strong space charge layer is characterized by a scaled Debye length, which is larger than [math]. We find that both layers exhibit distinct behavior; we see quadratic behavior in the strong space charge layer and exponential behavior in the weak space charge layer. We find that matching between these two asymptotic regimes is not standard, and we implement a pseudomatching approach to facilitate the transition between the quadratic and exponential behaviors. We demonstrate excellent agreement between asymptotics and simulation.
{"title":"An Asymptotic Analysis of Space Charge Layers in a Mathematical Model of a Solid Electrolyte","authors":"Laura M. Keane, Iain R. Moyles","doi":"10.1137/23m1580954","DOIUrl":"https://doi.org/10.1137/23m1580954","url":null,"abstract":"SIAM Journal on Applied Mathematics, Volume 84, Issue 4, Page 1413-1438, August 2024. <br/> Abstract. We review a model for a solid electrolyte derived under thermodynamics principles. We nondimensionalize and scale the model to identify small parameters where we identify a scaling that controls the width of the space charge layer in the electrolyte. We present asymptotic analyses and numerical solutions for the one-dimensional zero charge flux equilibrium problem. We introduce an auxiliary variable to remove singularities from the domain in order to facilitate robust numerical simulations. From the asymptotics, we identify three distinct regions: bulk, boundary, and intermediate layers. The boundary and intermediate layers form the space charge layer of the solid electrolyte, which we can further distinguish as strong and weak space charge layers, respectively. The weak space charge layer is characterized by a length, [math], which is equivalent to the Debye length of a standard liquid electrolyte. The strong space charge layer is characterized by a scaled Debye length, which is larger than [math]. We find that both layers exhibit distinct behavior; we see quadratic behavior in the strong space charge layer and exponential behavior in the weak space charge layer. We find that matching between these two asymptotic regimes is not standard, and we implement a pseudomatching approach to facilitate the transition between the quadratic and exponential behaviors. We demonstrate excellent agreement between asymptotics and simulation.","PeriodicalId":51149,"journal":{"name":"SIAM Journal on Applied Mathematics","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141549443","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
SIAM Journal on Applied Mathematics, Volume 84, Issue 4, Page 1385-1412, August 2024. Abstract. This paper aims to present a novel isotropic bidirectional model for studying weakly dispersive and weakly nonlinear atmospheric internal waves in a three-dimensional system consisting of two superimposed, incompressible, and inviscid fluids. The newly developed equation is the Benjamin–Benney–Luke (BBL) equation, a generalization of the famous two-dimensional Benjamin–Ono (2DBO) equation and the Benney–Luke equation, derived using the nonlocal Ablowitz–Fokas–Musslimani formulation of water waves. The evolution results of the BBL and 2DBO equations, performed by implementing the classic fourth-order Runge–Kutta method, the pseudospectral scheme with the integrating factor method, and the windowing scheme, show that the anisotropic 2DBO equation agrees well with the isotropic BBL model for problems being investigated, namely the focus is the central part of the soliton evolution/interaction zone. By applying the Whitham modulation theory, modulation equations for the 2DBO equation are obtained in this paper for analyzing the soliton dynamics in five different initial-value problems (truncated line soliton, line soliton, bent-stem soliton, bent soliton, and reverse bent soliton). In addition, corresponding numerical results are obtained and shown to agree well with the theoretical predictions. Both theoretical and numerical results reveal the formation conditions of the Mach expansion, as well as the specific relationship between the amplitude of the Mach stem and the initial data.
{"title":"Diffraction and Interaction of Interfacial Solitons in a Two-Layer Fluid of Great Depth","authors":"Lei Hu, Xu-Dan Luo, Zhan Wang","doi":"10.1137/23m1572349","DOIUrl":"https://doi.org/10.1137/23m1572349","url":null,"abstract":"SIAM Journal on Applied Mathematics, Volume 84, Issue 4, Page 1385-1412, August 2024. <br/> Abstract. This paper aims to present a novel isotropic bidirectional model for studying weakly dispersive and weakly nonlinear atmospheric internal waves in a three-dimensional system consisting of two superimposed, incompressible, and inviscid fluids. The newly developed equation is the Benjamin–Benney–Luke (BBL) equation, a generalization of the famous two-dimensional Benjamin–Ono (2DBO) equation and the Benney–Luke equation, derived using the nonlocal Ablowitz–Fokas–Musslimani formulation of water waves. The evolution results of the BBL and 2DBO equations, performed by implementing the classic fourth-order Runge–Kutta method, the pseudospectral scheme with the integrating factor method, and the windowing scheme, show that the anisotropic 2DBO equation agrees well with the isotropic BBL model for problems being investigated, namely the focus is the central part of the soliton evolution/interaction zone. By applying the Whitham modulation theory, modulation equations for the 2DBO equation are obtained in this paper for analyzing the soliton dynamics in five different initial-value problems (truncated line soliton, line soliton, bent-stem soliton, bent soliton, and reverse bent soliton). In addition, corresponding numerical results are obtained and shown to agree well with the theoretical predictions. Both theoretical and numerical results reveal the formation conditions of the Mach expansion, as well as the specific relationship between the amplitude of the Mach stem and the initial data.","PeriodicalId":51149,"journal":{"name":"SIAM Journal on Applied Mathematics","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141552941","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
SIAM Journal on Applied Mathematics, Volume 84, Issue 4, Page 1312-1336, August 2024. Abstract. Pine wilt disease is one of the most serious forest diseases and pests in China, which seriously influences the realization of the goal of “carbon peak and carbon neutrality.” In our article, we divide longhorns into susceptible ones and infected ones since pine wilt disease is spread by longhorns. Considering the saturation incidence of pine wilt disease, we establish a delayed reaction-diffusion model with nonlocal effect for susceptible and infected longhorns. First, we consider the well-posedness of solutions and the type of equilibria for the nonspatial system. Next, we discuss the dynamics of the spatial system with nonlocal effect. According to the multiple time scales method, we derive the normal form of Hopf bifurcation for a system associated with nonlocal effect, and the stability and direction of bifurcating periodic solutions are analyzed. Finally, using real data for China to perform data analysis, we select suitable values of parameters. Numerical simulations are presented to illustrate the ecological significance. Combined with the current situation, we provide some theoretical support for the prevention and control of pine wilt disease in China. Especially, we find that the nonlocal term can induce spatially stable inhomogeneous bifurcating periodic solutions.
{"title":"Spatiotemporal Dynamic Analysis of Delayed Diffusive Pine Wilt Disease Model with Nonlocal Effect","authors":"Yanchuang Hou, Yuting Ding","doi":"10.1137/23m1575305","DOIUrl":"https://doi.org/10.1137/23m1575305","url":null,"abstract":"SIAM Journal on Applied Mathematics, Volume 84, Issue 4, Page 1312-1336, August 2024. <br/> Abstract. Pine wilt disease is one of the most serious forest diseases and pests in China, which seriously influences the realization of the goal of “carbon peak and carbon neutrality.” In our article, we divide longhorns into susceptible ones and infected ones since pine wilt disease is spread by longhorns. Considering the saturation incidence of pine wilt disease, we establish a delayed reaction-diffusion model with nonlocal effect for susceptible and infected longhorns. First, we consider the well-posedness of solutions and the type of equilibria for the nonspatial system. Next, we discuss the dynamics of the spatial system with nonlocal effect. According to the multiple time scales method, we derive the normal form of Hopf bifurcation for a system associated with nonlocal effect, and the stability and direction of bifurcating periodic solutions are analyzed. Finally, using real data for China to perform data analysis, we select suitable values of parameters. Numerical simulations are presented to illustrate the ecological significance. Combined with the current situation, we provide some theoretical support for the prevention and control of pine wilt disease in China. Especially, we find that the nonlocal term can induce spatially stable inhomogeneous bifurcating periodic solutions.","PeriodicalId":51149,"journal":{"name":"SIAM Journal on Applied Mathematics","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141521645","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
SIAM Journal on Applied Mathematics, Volume 84, Issue 4, Page 1288-1311, August 2024. Abstract. In this paper, we solve an inverse resonance problem for the half-solid with vanishing stresses on the surface: Lamb’s problem. Using a semiclassical approach, we are able to simplify this three-dimensional problem of the elastic wave equation for the half-solid as a Schrödinger equation with Robin boundary conditions on the half-line. We obtain asymptotic values on the number and the location of the resonances with respect to the wave number. Moreover, we prove that the mapping from real compactly supported potentials to the Jost functions in a suitable class of entire functions is one-to-one and onto and we produce an algorithm in order to retrieve the shear modulus from the eigenvalues and resonances.
{"title":"Inverse Resonance Problem for Love Seismic Surface Waves","authors":"Samuele Sottile","doi":"10.1137/23m155877x","DOIUrl":"https://doi.org/10.1137/23m155877x","url":null,"abstract":"SIAM Journal on Applied Mathematics, Volume 84, Issue 4, Page 1288-1311, August 2024. <br/> Abstract. In this paper, we solve an inverse resonance problem for the half-solid with vanishing stresses on the surface: Lamb’s problem. Using a semiclassical approach, we are able to simplify this three-dimensional problem of the elastic wave equation for the half-solid as a Schrödinger equation with Robin boundary conditions on the half-line. We obtain asymptotic values on the number and the location of the resonances with respect to the wave number. Moreover, we prove that the mapping from real compactly supported potentials to the Jost functions in a suitable class of entire functions is one-to-one and onto and we produce an algorithm in order to retrieve the shear modulus from the eigenvalues and resonances.","PeriodicalId":51149,"journal":{"name":"SIAM Journal on Applied Mathematics","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141521643","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
SIAM Journal on Applied Mathematics, Volume 84, Issue 4, Page 1255-1287, August 2024. Abstract. Generative adversarial networks (GANs) have enjoyed tremendous success in image generation and processing and have recently attracted growing interest in financial modeling. This paper analyzes GANs from the perspectives of mean-field games (MFGs) and optimal transport: GANs are interpreted as MFGs under the Pareto optimality criterion or mean-field controls; meanwhile, GANs are to minimize the optimal transport cost indexed by the generator from the known latent distribution to the unknown true distribution of data. In particular, we provide a universal approximation result, which shows that there exists an appropriate neural network architecture for GANs training to capture the mean-field solution. The derivation of this universal approximation result leads to an explicit construction of the deep neural network for the transport mapping. The MFGs perspective of GANs leads to a GAN-based computational method (MFGANs) to solve MFGs: one neural network for the backward Hamilton–Jacobi–Bellman equation and one neural network for the forward Fokker–Planck equation, with the two neural networks trained in an adversarial way. Numerical experiments demonstrate superior performance of this proposed algorithm, especially in higher dimensional cases, when compared with existing neural network approaches.
{"title":"Connecting GANs, Mean-Field Games, and Optimal Transport","authors":"Haoyang Cao, Xin Guo, Mathieu Laurière","doi":"10.1137/22m1499534","DOIUrl":"https://doi.org/10.1137/22m1499534","url":null,"abstract":"SIAM Journal on Applied Mathematics, Volume 84, Issue 4, Page 1255-1287, August 2024. <br/> Abstract. Generative adversarial networks (GANs) have enjoyed tremendous success in image generation and processing and have recently attracted growing interest in financial modeling. This paper analyzes GANs from the perspectives of mean-field games (MFGs) and optimal transport: GANs are interpreted as MFGs under the Pareto optimality criterion or mean-field controls; meanwhile, GANs are to minimize the optimal transport cost indexed by the generator from the known latent distribution to the unknown true distribution of data. In particular, we provide a universal approximation result, which shows that there exists an appropriate neural network architecture for GANs training to capture the mean-field solution. The derivation of this universal approximation result leads to an explicit construction of the deep neural network for the transport mapping. The MFGs perspective of GANs leads to a GAN-based computational method (MFGANs) to solve MFGs: one neural network for the backward Hamilton–Jacobi–Bellman equation and one neural network for the forward Fokker–Planck equation, with the two neural networks trained in an adversarial way. Numerical experiments demonstrate superior performance of this proposed algorithm, especially in higher dimensional cases, when compared with existing neural network approaches.","PeriodicalId":51149,"journal":{"name":"SIAM Journal on Applied Mathematics","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141521646","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
SIAM Journal on Applied Mathematics, Volume 84, Issue 4, Page 1362-1384, August 2024. Abstract. We propose to study an inverse problem of determining multiple anomalies embedded in a multilayered background medium by the associated electric measurement which arises in Electrical Impedance Tomography (EIT). There are several salient features of our study. First, the anomaly considered in our study is extremely general which is characterized by its location, support, varying size, conductivity parameter, as well as a carry-on source intensity. Second, we make use of the measurement of the electric field generated by the active anomalies. This corresponds to a single passive measurement. Third, the background medium is of a multilayered and piecewise-constant structure and can be used to model a more general scenario from practical applications; say, e.g., the human body. Under the condition that the anomalies are small, but still in multiple scales considering their varying sizes, we derive a sharp formula of the electric field in terms of the polarization tensors, which enables us to establish comprehensive unique identifiability results in determining the characteristic parameters of the active anomalies in different situations.
{"title":"Identifying Active Anomalies in a Multilayered Medium by Passive Measurement in EIT","authors":"Youjun Deng, Hongyu Liu, Yajuan Wang","doi":"10.1137/23m1599458","DOIUrl":"https://doi.org/10.1137/23m1599458","url":null,"abstract":"SIAM Journal on Applied Mathematics, Volume 84, Issue 4, Page 1362-1384, August 2024. <br/> Abstract. We propose to study an inverse problem of determining multiple anomalies embedded in a multilayered background medium by the associated electric measurement which arises in Electrical Impedance Tomography (EIT). There are several salient features of our study. First, the anomaly considered in our study is extremely general which is characterized by its location, support, varying size, conductivity parameter, as well as a carry-on source intensity. Second, we make use of the measurement of the electric field generated by the active anomalies. This corresponds to a single passive measurement. Third, the background medium is of a multilayered and piecewise-constant structure and can be used to model a more general scenario from practical applications; say, e.g., the human body. Under the condition that the anomalies are small, but still in multiple scales considering their varying sizes, we derive a sharp formula of the electric field in terms of the polarization tensors, which enables us to establish comprehensive unique identifiability results in determining the characteristic parameters of the active anomalies in different situations.","PeriodicalId":51149,"journal":{"name":"SIAM Journal on Applied Mathematics","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141508785","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
SIAM Journal on Applied Mathematics, Volume 84, Issue 4, Page 1337-1361, August 2024. Abstract. The generalized nonlinear Schrödinger equation with full dispersion (FDNLS) is considered in the semiclassical regime. The Whitham modulation equations are obtained for the FDNLS equation with general linear dispersion and a generalized, local nonlinearity. Assuming the existence of a four-parameter family of two-phase solutions, a multiple-scales approach yields a system of four independent, first-order, quasi-linear conservation laws of hydrodynamic type that correspond to the slow evolution of the two wavenumbers, mass, and momentum of modulated periodic traveling waves. The modulation equations are further analyzed in the dispersionless and weakly nonlinear regimes. The ill-posedness of the dispersionless equations corresponds to the classical criterion for modulational instability (MI). For modulations of linear waves, ill-posedness coincides with the generalized MI criterion, recently identified by Amiranashvili and Tobisch [New J. Phys., 21 (2019), 033029]. A new instability index is identified by the transition from real to complex characteristics for the weakly nonlinear modulation equations. This instability is associated with long wavelength modulations of nonlinear two-phase wavetrains and can exist even when the corresponding one-phase wavetrain is stable according to the generalized MI criterion. Another interpretation is that while infinitesimal perturbations of a periodic wave may not grow, small but finite amplitude perturbations may grow, hence this index identifies a nonlinear instability mechanism for one-phase waves. Classifications of instability indices for multiple FDNLS equations with higher-order dispersion, including applications to finite-depth water waves and the discrete NLS equation, are presented and compared with direct numerical simulations.
{"title":"Whitham Modulation Theory and Two-Phase Instabilities for Generalized Nonlinear Schrödinger Equations with Full Dispersion","authors":"Patrick Sprenger, Mark A. Hoefer, Boaz Ilan","doi":"10.1137/23m1603078","DOIUrl":"https://doi.org/10.1137/23m1603078","url":null,"abstract":"SIAM Journal on Applied Mathematics, Volume 84, Issue 4, Page 1337-1361, August 2024. <br/> Abstract. The generalized nonlinear Schrödinger equation with full dispersion (FDNLS) is considered in the semiclassical regime. The Whitham modulation equations are obtained for the FDNLS equation with general linear dispersion and a generalized, local nonlinearity. Assuming the existence of a four-parameter family of two-phase solutions, a multiple-scales approach yields a system of four independent, first-order, quasi-linear conservation laws of hydrodynamic type that correspond to the slow evolution of the two wavenumbers, mass, and momentum of modulated periodic traveling waves. The modulation equations are further analyzed in the dispersionless and weakly nonlinear regimes. The ill-posedness of the dispersionless equations corresponds to the classical criterion for modulational instability (MI). For modulations of linear waves, ill-posedness coincides with the generalized MI criterion, recently identified by Amiranashvili and Tobisch [New J. Phys., 21 (2019), 033029]. A new instability index is identified by the transition from real to complex characteristics for the weakly nonlinear modulation equations. This instability is associated with long wavelength modulations of nonlinear two-phase wavetrains and can exist even when the corresponding one-phase wavetrain is stable according to the generalized MI criterion. Another interpretation is that while infinitesimal perturbations of a periodic wave may not grow, small but finite amplitude perturbations may grow, hence this index identifies a nonlinear instability mechanism for one-phase waves. Classifications of instability indices for multiple FDNLS equations with higher-order dispersion, including applications to finite-depth water waves and the discrete NLS equation, are presented and compared with direct numerical simulations.","PeriodicalId":51149,"journal":{"name":"SIAM Journal on Applied Mathematics","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141521644","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
SIAM Journal on Applied Mathematics, Volume 84, Issue 3, Page 1227-1253, June 2024. Abstract. We consider planar traveling fronts between stable steady states in two-component singularly perturbed reaction-diffusion-advection equations, where a small quantity [math] represents the ratio of diffusion coefficients. The fronts under consideration are large amplitude and contain a sharp interface, induced by traversing a fast heteroclinic orbit in a suitable slow-fast framework. We explore the effect of advection on the spectral stability of the fronts to long wavelength perturbations in two spatial dimensions. We find that for suitably large advection coefficient [math], the fronts are stable to such perturbations, while they can be unstable for smaller values of [math]. In this case, a critical asymptotic scaling [math] is obtained at which the onset of instability occurs. The results are applied to a family of traveling fronts in a dryland ecosystem model.
{"title":"A Stabilizing Effect of Advection on Planar Interfaces in Singularly Perturbed Reaction-Diffusion Equations","authors":"Paul Carter","doi":"10.1137/23m1610872","DOIUrl":"https://doi.org/10.1137/23m1610872","url":null,"abstract":"SIAM Journal on Applied Mathematics, Volume 84, Issue 3, Page 1227-1253, June 2024. <br/> Abstract. We consider planar traveling fronts between stable steady states in two-component singularly perturbed reaction-diffusion-advection equations, where a small quantity [math] represents the ratio of diffusion coefficients. The fronts under consideration are large amplitude and contain a sharp interface, induced by traversing a fast heteroclinic orbit in a suitable slow-fast framework. We explore the effect of advection on the spectral stability of the fronts to long wavelength perturbations in two spatial dimensions. We find that for suitably large advection coefficient [math], the fronts are stable to such perturbations, while they can be unstable for smaller values of [math]. In this case, a critical asymptotic scaling [math] is obtained at which the onset of instability occurs. The results are applied to a family of traveling fronts in a dryland ecosystem model.","PeriodicalId":51149,"journal":{"name":"SIAM Journal on Applied Mathematics","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141508786","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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