Vu Hoang, Maria Radosz
The $α$-patch model is used to study aspects of fluid equations. We show that solutions of this model form singularities in finite time and give a characterization of the solution profile at the singular time.
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We investigate the singularity formation of a nonlinear nonlocal system. This nonlocal system is a simplified one-dimensional system of the 3D model that was recently proposed by Hou and Lei in [13] for axisymmetric 3D incompressible Navier-Stokes equations with swirl. The main difference between the 3D model of Hou and Lei and the reformulated 3D Navier-Stokes equations is that the convection term is neglected in the 3D model. In the nonlocal system we consider in this paper, we replace the Riesz operator in the 3D model by the Hilbert transform. One of the main results of this paper is that …
In this article, we will prove the existence of infinitely many positive weak solutions to the following nonlocal elliptic PDE. \begin{align} (-Δ)^s u&= \fracλ{u^γ}+ f(x,u)~\text{in}~Ω,\nonumber u&=0~\text{in}~\mathbb{R}^N\setminusΩ,\nonumber \end{align} where $Ω$ is an open bounded domain in $\mathbb{R}^N$ with Lipschitz boundary, $N>2s$, $s\in (0,1)$, $γ\in (0,1)$. We will employ variational techniques to show the existence of infinitely many weak solutions of the above problem.
We study a 1D fluid mechanics model with nonlocal velocity. The equation can be viewed as a fractional porous medium flow, a 1D model of the quasi-geostrophic equation, and also a special case of Euler-Alignment system. For strictly positive smooth initial data, global regularity has been proved by Do, Kiselev, Ryzhik and Tan. We construct a family of non-negative smooth initial data so that solution loses $C^1$ regularity. Our result indicates that strict positivity is a critical condition to ensure global regularity of the system. We also extend our construction to the corresponding models i…
In this paper, we prove the existence of multiple solutions for a nonlinear nonlocal elliptic PDE involving a singularity which is given as \begin{eqnarray} (-Δ_p)^s u&=& \fracλ{u^γ}+u^q~\text{in}~Ω,\nonumber u&=&0~\text{in}~\mathbb{R}^N\setminusΩ,\nonumber u&>& 0~\text{in}~Ω\nonumber, \end{eqnarray} where $Ω$ is an open bounded domain in $\mathbb{R}^N$ with smooth boundary, $N>ps$, $s\in (0,1)$, $λ>0$, $0<γ<1$, $1<p<\infty$, $p-1<q\leq p_s^{*}=\frac{Np}{N-ps}$. We employ variational techniques to show the existence of multiple positive weak solutions of the above problem. We also prove that f…
We propose some one-dimensional reduced models for the three-dimensional electron magnetohydrodynamics which involves a highly nonlinear Hall term with intricate structure. The models contain nonlocal nonlinear terms. Local well-posedness is obtained in certain circumstances. In contrast, for a model with nonlocal transport term, we show that finite time singularity may occur for some initial data.
We give an application of the Crandall-Rabinowitz theorem on local bifurcation to a system of nonlinear parabolic equations with nonlocal reaction and cross-diffusion terms as well as nonlocal initial conditions. The system arises as steady-state equations of two interacting age-structured populations.
In this paper we study the Burgers equation with a nonlocal term of the form $Hu$ where $H$ is the Hilbert transform. This system has been considered as a quadratic approximation for the dynamics of a free boundary of a vortex patch. We prove blow up in finite time for a large class of initial data with finite energy. Considering a more general nonlocal term, of the form $Λ^αHu$ for $0<α< 1$, finite time singularity formation is also shown.
In this paper, we prove that the solution maps of a large class of nonlocal dispersal equations are $α$-contractions, where $α$ is the Kuratowski measure of noncompactness. Then we give some remarks on the spreading speeds and traveling waves for such evolution equations in a periodic habitat.
In this note we prove an estimate on the level sets of a function with $(p, q)$ growth that depends on the difference quotient of a bounded weak solution to a nonlocal double phase equation. This estimate is related to a self improving property of these solutions.
Numerical simulation of singularity propagation modeled by linear convection equations with spatially heterogeneous nonlocal interactions
该研究针对带空间异质性非局部相互作用的线性对流方程，解析推导了非局部区域奇异性传播的刻画方程，并用渐近相容格式离散开展数值模拟，揭示异质性与局部-非局部转换对奇异性传播的影响。
Finite time singularity formation for a nonlocal Boussinesq system arising in cold-plasma dynamics
研究冷等离子体动力学中非局部Boussinesq系统的有限时间奇点形成，证明特定初始数据导致爆破，并给出生命跨度上界及速度梯度无界性。
A clarification on the distinction between nonlocal error and profile residual error in a computer-assisted proof of 3D Euler singularity
本注针对三维欧拉奇点计算机辅助证明，澄清非局部误差与剖面残差误差的区别，并指出相关文献的证据无法否定已有残差估计，也不支持角增长假设在Hou-Luo场景下的适用性。
A note on nonlocal approximations of sign-unrestricted solutions of conservation laws
本文研究非局部守恒律的奇异极限，证明当核趋于狄拉克分布时非局部解收敛到局部熵解，推广了符号限制情形，涵盖广义Burgers方程和Keyfitz--Kranzer系统。
Regularity of Solutions for the Nonlocal Wave Equation on Periodic Distributions
本文利用傅里叶乘子方法研究周期分布上非局部波动方程解的正则性，覆盖正则解与分布解、可积核与奇异核，并证明解在非局部性消失或核奇异性趋于临界值时收敛到经典波动方程的解。
This work addresses the regularity of solutions for a nonlocal diffusion equation over the space of periodic distributions. The spatial operator for the nonlocal diffusion equation is given by a nonlocal Laplace operator with a compactly supported integral kernel. We follow a unified approach based on the Fourier multipliers of the nonlocal Laplace operator, which allows the study of regular as well as distributional solutions of the nonlocal diffusion equation, integrable as well as singular kernels, in any spatial dimension. In addition, the results extend beyond operators with singular kern…
Existence results for mixed local and nonlocal elliptic equations involving singularity and nonregular data
针对含奇异性与测度数据的混合局部-非局部椭圆方程，运用Schauder不动点定理、Marcinkiewicz空间嵌入等工具，证明弱解、极弱解与对偶解的存在性，拓展了相关算子的已有研究。
We prove the existence of ground state solution to the following problem. \begin{align*} (-Δ)^{s}u+u&=λ|u|^{-γ-1}u+P(x)|u|^{p-1}u,~\text{in}~\mathbb{R}^N\setminusΩ\\ N_su(x)&=0,~\text{in}~Ω\end{align*} where $N\geq2$, $λ>0$, $0<s,γ<1$, $p\in(1,2_s^*-1)$ with $2_s^*=\frac{2N}{N-2s}$. % $0<s^-=\underset{(x,y)\inΩ\timesΩ}{\inf}\{s(x,y)\}\leq s(x,y)\leq s^+=\underset{(x,y)\inΩ\timesΩ}{\sup}\{s(x,y)\}<1$, $0<γ^-=\underset{x\inΩ}{\inf}\{γ(x)\}\leq γ(x)\leq γ^+=\underset{x\inΩ}{\sup}\{γ(x)\}<1$, $1-γ^-<1<p^-=\underset{x\inΩ}{\inf}\{p(x)\}\leq p(x)\leq p^+=\underset{x\inΩ}{\sup}\{p(x)\}<2_{s^-}^*=\und…
We study a 1D transport equation with nonlocal velocity and show the formation of singularities in finite time for a generic family of initial data. By adding a diffusion term the finite time singularity is prevented and the solutions exist globally in time.
The occurrence of a finite time singularity is shown for a free boundary problem modeling microelectromechanical systems (MEMS) when the applied voltage exceeds some value. The model involves a singular nonlocal reaction term and a nonlinear curvature term accounting for large deformations.
Pseudo-differential noise and nonlocal singularity formation in the stochastic Córdoba--Córdoba--Fontelos equation
该研究针对乘性Stratonovich噪声驱动的随机Córdoba--Córdoba--Fontelos方程，建立了极大经典解的局部时间理论，证明有限时间爆破的相关性质并确定了爆破速率，为该类方程的奇异性研究提供了理论支撑。
Singularities of solutions of nonlocal nonlinear equations
本文研究非局部非线性方程弱解的局部奇异性，证明零容量集合在可积性条件下可去，并用基本解刻画孤立奇点附近的渐近行为。
Let $Ω\subset \mathbb{R}^n $ be any open set and $u$ be a weak supersolution of $\mathcal{L}u=c(x)g(|u|)\frac{u}{|u|}$ where \[\mathcal{L}u(x)=\text{p.v.} \int_{\mathbb{R}^n} g\left(\frac{|u(x)-u(y)|}{|x-y|^s}\right) \frac{u(x)-u(y)}{|u(x)-u(y)|} K(x,y)\frac{dy}{|x-y|^s}\] and $g=G^{\prime}$ for some Young function $G.$ This note imparts a Hopf's type lemma and strong minimum principle for $u$ when $c(x)$ is continuous in $\barΩ$ that extend the results of Del Pezzo and Quaas (JDE-2017) in fractional Orlicz-Sobolev setting.
Lecture notes: Biological propagation via reaction-diffusion equations with nonlocal diffusion and free boundary
本讲义基于VIASM 2025暑期学校课程，介绍一维带自由边界的非局部反应扩散传播理论，围绕KPP反应项展开，并将对称核函数的相关技术扩展至弱非对称情形，给出完整证明细节。
We study the formation of singularities for the Euler-Alignment system with influence function $ψ=\frac{k_α}{|x|^α}$ in 1D. As in [20] the problem is reduced to the analysis of a nonlocal 1D equation. We show the existence of singularities in finite time for any $α$ in the range $0<α<2$ in both the real line and the periodic case.
In this note, we introduce some models of pedestrian traffic and prove existence and uniqueness for these models.
We study Dirichlet forms defined by nonintegrable Lévy kernels whose singularity at the origin can be weaker than that of any fractional Laplacian. We show some properties of the associated Sobolev type spaces in a bounded domain, such as symmetrization estimates, Hardy inequalities, compact inclusion in $L^2$ or the inclusion in some Lorentz space. We then apply those properties to study the associated nonlocal operator $\mathfrak{L}$ and the Dirichlet and Neumann problems related to the equations $\mathfrak{L}u=f(x)$ and $\mathfrak{L}u=f(u)$ in $Ω$.
Continuity of solutions to equations with weakly singular nonlocal operators
本文研究涉及几乎无可微性阶积分微分算子的线性非局部方程，证明了有界弱解的连续性并给出了一致的连续性模先验估计，同时允许算子高度各向异性、弱奇异且核函数在奇点附近消失。
Simple applications of a principle of minimum energy and the property of monotonicity for the corresponding non-local operator, have allowed a direct proof of the G-compactness in a weak sense, as well as in the strong sense. The definitions of H-convergence and G-convergence, weak or strong, have been proved to be equivalent.
Two-species system with nonlocal interactions driven by Riesz potentials
本文研究了通过Riesz型势能耦合的双物种非局部连续方程系统，通过最优运输理论和Wasserstein空间中的梯度流理论，证明了在交叉相互作用满足对称条件时，弱解的存在性。
We provide sufficient conditions on an initial curve for the area preserving and the length preserving curvature flows of curves in a plane, to develop a singularity at some finite time or converge to an $m$-fold circle as time goes to infinity. For the area-preserving flow, the positivity of the enclosed algebraic area determines whether the curvature blows up in finite time or not, while for the length-preserving flow, it is the positivity of an energy associated with initial curve that plays such a role.
We study the existence of non-trivial, non-negative periodic solutions for systems of singular-degenerate parabolic equations with nonlocal terms and satisfying Dirichlet boundary conditions. The method employed in this paper is based on the Leray-Schauder topological degree theory. However, verifying the conditions under which such a theory applies is more involved due to the presence of the singularity. The system can be regarded as a possible model of the interactions of two biological species sharing the same isolated territory, and our results give conditions that ensure the coexistence o…
We study integrodifferential operators and regularity estimates for solutions to integrodifferential equations. Our emphasis is on kernels with a critically low singularity which does not allow for standard scaling. For example, we treat operators that have a logarithmic order of differentiability. For corresponding equations we prove a growth lemma and derive a priori estimates. We derive these estimates by classical methods developed for partial differential operators. Since the integrodifferential operators under consideration generate Markov jump processes, we are able to offer an alternat…
We consider a class of nonlocal viscous Cahn-Hilliard equations with Neumann boundary conditions for the chemical potential. The double-well potential is allowed to be singular (e.g. of logarithmic type), while the singularity of the convolution kernel does not fall in any available existence theory under Neumann boundary conditions. We prove well-posedness for the nonlocal equation in a suitable variational sense. Secondly, we show that the solutions to the nonlocal equation converge to the corresponding solutions to the local equation, as the convolution kernels approximate a Dirac delta. Th…
In this note we consider the 1-D cubic Schrödinger equation with data given as small perturbations of a Dirac-$δ$ function and some other related equations. We first recall that although the problem for this type of data is ill-posed one can use the geometric framework of the Schrödinger map to define the solution beyond the singularity time. Then, we find some natural and well defined geometric quantities that are not regular at time zero. Finally, we make a link between these results and some known phenomena in fluid mechanics that inspired this note.
In this note we prove that appropriately scaled threshold dynamics-type algorithms corresponding to the fractional Laplacian of order $α\in (0,2)$ converge to moving fronts. When $α\geqq 1$ the resulting interface moves by weighted mean curvature, while for $α<1$ the normal velocity is nonlocal of ``fractional-type.'' The results easily extend to general nonlocal anisotropic threshold dynamics schemes.
We derive uniform in time $L^\infty$-bound for solutions to an aggregation-diffusion model with attractive-repulsive potentials or fully attractive potentials. We analyze two cases: either the repulsive nonlocal term dominates over the attractive part, or the diffusion term dominates over the fully attractive nonlocal part. When the attractive potential has a weaker singularity ($2-n\leq B<A\leq2$), we use the classical approach by the Sobolev and Young inequalities together with differential iterative inequalities to prove that solutions have the uniform in time $L^{\infty}$-bound. When the r…
In this note, we want to highlight and correct an error in the paper "On the nonlocal Cahn-Hilliard-Brinkman and Cahn-Hilliard-Hele-Shaw systems" [Comm. Pure Appl. Anal. 15 (2016), 299-317] written by the authors.
In this note we set up the elliptic and the parabolic Dirichlet problem for linear nonlocal operators. As opposed to the classical case of second order differential operators, here the "boundary data" are prescribed on the complement of a given bounded set. We formulate the problem in the classical framework of Hilbert spaces and prove unique solvability using standard techniques like the Fredholm alternative.
We investigate the decay for $|x|\rightarrow \infty$ of weak Sobolev type solutions of semilinear nonlocal equations $Pu=F(u)$. We consider the case when $P=p(D)$ is an elliptic Fourier multiplier with polyhomogeneous symbol $p(ξ)$ and derive sharp algebraic decay estimates in terms of weighted Sobolev norms. In particular, we state a precise relation between the singularity of the symbol at the origin and the rate of decay of the corresponding solutions. Our basic example is the celebrated Benjamin-Ono equation {equation} \label{BO}(|D|+c)u=u^2, \qquad c>0,{equation} for internal solitary wav…
We discuss in this note the stickiness phenomena for nonlocal minimal surfaces. Classical minimal surfaces in convex domains do not stick to the boundary of the domain, hence examples of stickiness can be obtained only by removing the assumption of convexity. On the other hand, in the nonlocal framework, stickiness is "generic". We provide various examples from the literature, and focus on the case of complete stickiness in highly nonlocal regimes.
We study the nonlinear and nonlocal Cauchy problem \[ \partial_{t}u+\mathcal{L}φ(u)=0 \quad\text{in }\mathbb{R}^{N}\times\mathbb{R}_+,\qquad u(\cdot,0)=u_0, \] where $\mathcal{L}$ is a Lévy-type nonlocal operator with a kernel having a singularity at the origin as that of the fractional Laplacian. The nonlinearity $φ$ is nondecreasing and continuous, and the initial datum $u_0$ is assumed to be in $L^1(\mathbb{R}^N)$. We prove existence and uniqueness of weak solutions. For a wide class of nonlinearities, including the porous media case, $φ(u)=|u|^{m-1}u$, $m>1$, these solutions turn out to be…
In this note we consider the pointwise convergence to the initial data for the solutions of some nonlocal dyadic Schrödinger equations on spaces of homogeneous type. We prove the a.e. convergence when the initial data belongs to a dyadic version of an $L^2$ based Besov space.
Removable singularities for nonlocal minimal graphs
本文研究了非局部极小图在特定条件下的可移除奇点问题，证明了在满足容量为零的条件下，非局部极小图可扩展至整个区域。
We consider a nonlocal analogue of the Fisher-KPP equation. We do not assume that the Borel-measure for the convolution is absolutely continuous. In order to show the main result, we modify a recursive method for abstract monotone discrete dynamical systems by Weinberger. We note that the monotone semiflow generated by the equation does not have compactness with respect to the compact-open topology. At the end, we propose a discrete model that describes the measurement process.
A note on the $L^{p}$-solvability of a strongly-coupled nonlocal system of equations
本文通过连续性方法，研究了与核$K$（在$s\in(0,1)$时与$|\mathbf{y}|^{-(d+2s)}$相当）相关的线性非局部耦合向量值算子$\mathbb{L}$的$L^p$可解性，证明了对于任意$\mathbf{f}\in[L^p(\mathbb{R}^d)]^d$（$1<p<\infty$），存在唯一强解$\mathbf{u}\in[H^{2s,p}(\mathbb{R}^d)]^d$。
In this note, we give a positive answer to a question addressed in \cite{Nad-Per-Tan}. Precisely we prove that, for any kernel and any slope at the origin, there do exist travelling wave solutions (actually those which are "rapid") of the nonlocal Fisher equation that connect the two homogeneous steady states 0 (dynamically unstable) and 1. In particular this allows situations where 1 is unstable in the sense of Turing. Our proof does not involve any maximum principle argument and applies to kernels with {\it fat tails}.
We study metrics of constant $Q$-curvature in the Euclidean space with a prescribed singularity at the origin, namely solutions to the equation $$(-Δ)^\frac{n}{2}w=e^{nw}-cδ_{0} \text{ on } \mathbb R^n,$$ under a finite volume condition. We analyze the asymptotic behaviour at infinity and the existence of solutions for every $n\ge 3$ also in a supercritical regime. Finally, we state some open problems.
In this note we study the behaviour as $s\to 0^+$ of some semigroup based Besov seminorms associated with a non-symmetric and hypoelliptic diffusion with a drift. Our results generalise a previous one of Maz'ya and Shaposhnikova for the classical fractional Sobolev spaces $W^{s,p}$, and they also underscore a new phenomenon caused by the presence of the drift.
We prove the equivalence between the notion of Wasserstein gradient flow for a one-dimensional nonlocal transport PDE with attractive/repulsive Newtonian potential on one side, and the notion of entropy solution of a Burgers-type scalar conservation law on the other. The solution of the former is obtained by spatially differentiating the solution of the latter. The proof uses an intermediate step, namely the $L^2$ gradient flow of the pseudo-inverse distribution function of the gradient flow solution. We use this equivalence to provide a rigorous particle-system approximation to the Wasserstei…
In this note, we give a brief overview of obstacle problems for nonlocal operators, focusing on the applications to financial mathematics. The class of nonlocal operators that we consider can be viewed as infinitesimal generators of non-Gaussian asset price models, such as Variance Gamma Processes and Regular Lévy Processes of Exponential type. In this context, we analyze the existence, uniqueness and regularity of viscosity solutions to obstacle problems which correspond to prices of perpetual and finite expiry American options. Complete proofs can be found in arXiv:1709.10384, where these re…
A system of continuity equations with nonlocal interactions of Morse type
研究具有Morse型非局部相互作用的连续性方程组，通过Jordan-Kinderlehrer-Otto格式和梯度流理论证明解的存在唯一性与稳定性，并提出确定性粒子方案证明其收敛性。
A note on exterior stability of isolated singularity formation for nonlinear wave equations
研究非线性波映射方程和幂非线性波方程中I型和II型奇点形成外部的稳定性，通过特定初始数据和合适数据建立解的存在性，采用坐标变换和散射结果证明，探讨对称性限制的放宽。
In this note, we develop Fourier approximation methods for the solutions of first-order nonlocal mean-field games (MFG) systems. Using Fourier expansion techniques, we approximate a given MFG system by a simpler one that is equivalent to a convex optimization problem over a finite-dimensional subspace of continuous curves. Furthermore, we perform a time-discretization for this optimization problem and arrive at a finite-dimensional saddle point problem. Finally, we solve this saddle-point problem by a variant of a primal dual hybrid gradient method.
In this note, we propose a discrete model to study one-dimensional transport equations with non-local drift and supercritical dissipation. The inspiration for our model is the equation $$ θ_t + (Hθ) θ_x +(-Δ)^αθ=0 $$ where $H$ is the Hilbert transform. For our discrete model, we present blow-up results that are analogous to the known results for the above equation. In addition, we will prove regularity for our discrete model which suggests supercritical regularity in the range $1/4<α<1/2$ in the continuous setting.
A Note on Explicit Convergence Rates of Nonlocal Peridynamic Operators in $L^q$-Norm
本文利用 Hardy-Littlewood 极大函数与积分形式泰勒余项定理，在 $L^q$-范数下建立了非局部近场动力学偏导数及其散度、梯度、旋度算子向局部对应算子的显式收敛性，并得到 $\mathcal{O}(\delta^2)$ 阶收敛速率。
In this note we study the boundary regularity of solutions to nonlocal Dirichlet problems of the form $Lu=0$ in $Ω$, $u=g$ in $\mathbb R^N\setminusΩ$, in non-smooth domains $Ω$. When $g$ is smooth enough, then it is easy to transform this problem into an homogeneous Dirichlet problem with a bounded right hand side, for which the boundary regularity is well understood. Here, we study the case in which $g\in C^{0,α}$, and establish the optimal Hölder regularity of $u$ up to the boundary. Our results extend previous results of Grubb for $C^\infty$ domains $Ω$.
Fractional Sobolev spaces via interpolation, and applications to mixed local-nonlocal operators
本文介绍分数阶Sobolev空间与插值理论的关联，给出其作为Lebesgue与整数阶Sobolev空间间实/复插值空间的等价刻画，并用插值理论证明混合局部-非局部算子的谱定理，为早期研究者提供该领域简洁入门内容。
Li-Yau and Harnack estimates for nonlocal diffusion problems
本文介绍微分哈纳克不等式，总结了关于非局部扩散问题的李-尤和哈纳克估计的课程主要结果。
On some nonlocal, nonlinear diffusion problems
本文研究非局部非线性椭圆问题的解法，通过不动点论证和数值实验探讨解的计算与误差估计。
On Some Nonlocal in Time and Space Parabolic Problem
本文研究非局部时间与空间的非线性抛物型问题，探讨解的存在性、唯一性及渐进行为。
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