We study the Cauchy problem for the modified KdV equation for data u_0 in the space ^H^r_s defined by the norm ||u_0||_{^H^r_s}:=||<ξ>^s u^_0||_{L^r'_ξ}. Local well-posedness of this problem is established in the parameter range 2>=r>1, s>=1/2-1/2r, so the case (s,r)=(0,1), which is critical in view of scaling considerations is almost reached. To show this result, we use an appropriate variant of the Fourier restriction norm method as well as bi- and trilinear estimates for solutions of the Airy equation.
We construct modified energies for the generalized KdV equation. As a consequence, we obtain quasi-invariance of the high order Gaussian measures along with $L^p$ regularity on the corresponding Radon-Nykodim density, as well as new bounds on the growth of the Sobolev norms of the solutions.
Low regularity Cauchy problem for the fifth-order modified KdV equations on $\mathbb{T}$
本文研究了五阶修正KdV方程在周期边界条件下的解.利用能量方法证明了$H^s(\mathbb T)$，$s > 2$的局部适定性.主要工具是短时傅立叶限制范数方法，其首先由Ionescu、Kenig和Tataru以其当前形式引入[Global well-posedness of the KP-I初值问题in the energy space，Invent. 173（2）（2008）265- 304]。此外，我们使用频率局域化的修正能量来控制能量估计中的高低相互作用分量。我们注意到，在周期设置下，可积结构是非常有用的（但不是必要的），以消除有害的非线性项，这项工作是第一个低正则性适定性结果的五阶修正KdV方程。
The long time behavior of solutions to the defocusing modified Korteweg-de vries (MKdV) equation is established for initial conditions in some weighted Sobolev spaces. Our approach is based on the nonlinear steepest descent method of Deift and Zhou and its reformulation by Dieng and McLaughlin through $\overline{\partial}$-derivatives. To extend the asymptotics to solutions with initial data in lower regularity spaces, we apply a global approximation via PDE techniques.
In this work, we study the random series expansion of a multidimensional KdV type equation with a diffusion term, the so-called Zakharov-Kuznetsov (ZK) equation. We impose random initial data and periodic boundary condition with period $L$ on this equation. Using the random series expansion, we derive the $3$-wave kinetic equation on the inertial range for $t\lesssim L^{-\varepsilon}T_{\text{kin}}$. Our result reaches kinetic time scale up to $\varepsilon$ loss.
We study the well-posedness of the complex-valued modified Korteweg-de Vries equation (mKdV) on the circle at low regularity. In our previous work (2019), we introduced the second renormalized mKdV equation, based on the conservation of momentum, which we proposed as the correct model to study the complex-valued mKdV outside of $H^\frac12(\mathbb{T})$. Here, we employ the method introduced by Deng-Nahmod-Yue (2019) to prove local well-posedness of the second renormalized mKdV equation in the Fourier-Lebesgue spaces $\mathcal{F}L^{s,p}(\mathbb{T})$ for $s\geq \frac12$ and $1\leq p <\infty$. As …
We address two pressing questions in the theory of the Korteweg--de Vries (KdV) equation. First, we show the uniqueness of solutions to KdV that are merely bounded, without any further decay, regularity, periodicity, or almost periodicity assumptions. The second question, emphasized by Deift, regards whether almost periodic initial data leads to almost periodic solutions to KdV. Building on the new observation that this is false for the Airy equation, we construct an example of almost periodic initial data whose KdV evolution remains bounded, but fails to be almost periodic at a later time. Ou…
We prove global existence and modified scattering for the solutions of the generalized fifth-order KdV equation with critical nonlinearity for small and localized initial data. The proof is undergoing by using the space-time resonance method and the stationary phase argument.
We study the complex-valued modified Korteweg-de Vries equation (mKdV) on the circle. We first consider the real-valued setting and show global well-posedness of the (usual) renormalized mKdV equation in the Fourier-Lebesgue spaces. In the complex-valued setting, we observe that the momentum plays an important role in the well-posedness theory. In particular, we prove that the complex-valued mKdV equation is ill-posed in the sense of non-existence of solutions when the momentum is infinite, in the spirit of the work on the nonlinear Schrödinger equation by Guo-Oh (2018). This non-existence res…
Local well-posedness for the fifth-order KdV equations on $\mathbb{T}$
本文是论文\emph{Low regularity Cauchy problem for the fifth-order modified KdV equations on $\mathbb{T}$}的继续。本文考虑KdV族中的五阶方程：\begin{equation*} \begin{cases} \partial_t u - \partial_x^5 u + 30u^2\partial_x u + 20 u\partial_x u \partial_x^3u + 10u \partial_x^3 u = 0, \hspace{1em} (t,x) \in \mathbb{R} \times \mathbb{T}, u(0,x) = u_0(x) \in H^s(\mathbb{T}) \end{cases}. \end{equation*}我们利用能量方法证明了五阶KdV方程在低正则性Sobolev初值下的局部适定性。本文的思想和论点与文献\emph{Low regularity Cauchy problem for the fifth-order modified KdV equations on $\mathbb{T}$}基本相同。准确地说，我们利用KdV哈密顿量的某些守恒律来观察非线性解的演化方向。另外，在非共振非线性项中，由于\emph{high $\times$ lo…
We consider solutions of the generalized Korteweg-de Vries equations (gKdV) which are non dispersive in some sense (in the spirit of [18]) and which remain close to multi-solitons. We show that these solutions are necessarily pure multi-solitons. For the Korteweg-de Vries equation (KdV) and the modified Korteweg-de Vries equation (mKdV) in particular, we obtain a characterization of multi-solitons and multi-breathers in terms of non-dispersion.
New lower bounds on the radius of spatial analyticity for the KdV equation
研究了KdV方程解的空间解析性半径。结果表明，当时间$t$趋于无穷大时，解析性半径的衰减速度并不比$t^{-1/4}$快.这改进了工作[Selberg，da Silva，KdV方程空间解析性半径的下界，Annales Henri Poincaré，2017，18（3）：1009-1023]和[Tesfahun，KdV方程解的空间解析性半径的渐近下界，arXiv预印本arXiv：1707.07810，2017]。我们的策略主要依赖于Gevrey空间中的一个高阶概守恒律，这是受$I-$方法的启发。
Almost Periodicity in Time of Solutions of the KdV Equation
本文研究了KdV方程$\partial_t u - 6 u \partial_x u + \partial_x^3 u = 0$的Cauchy问题，其中初值为几乎周期初值$u(x,0)=V(x)$ .我们考虑初始数据$V$，其中相关的薛定谔算子是绝对连续的，并有一个频谱，是不是太薄，在某种意义上，我们指定，并显示的存在性，唯一性，几乎周期性的时间的解决方案。这建立了Percy Deift对这类初始数据的猜想。结果表明，适用于所有小的解析准周期初始数据与丢番图频率向量。
Periodic waves of the modified Korteweg-de Vries (mKdV) equation are identified in the context of a new variational problem with two constraints. The advantage of this variational problem is that its non-degenerate local minimizers are stable in the time evolution of the mKdV equation, whereas the saddle points are unstable. We explore the analytical representation of periodic waves given by Jacobi elliptic functions and compute numerically critical points of the constrained variational problem. A broken pitchfork bifurcation of three smooth solution families is found. Two families represent (…
Well-posedness and ill-posedness of the fifth order modifed KdV equation
在Sobolev空间上考虑五阶修正KdV方程的初值问题. \partial_t u = \partial_x^5 u + c_1 \partial_x^3（u^3）+\partial_x u + c_3uuPDMATHABMO u =0，u（x，0）= u_0（x）其中$ u:R\timesR \to R $和$c_j$是实数.利用$X^{s,b}$空间上的压缩原理证明了sPDMATHABMT 3/4在H^s（R）中的局部适定性.此外，我们表明，从数据到解决方案的解决方案映射未能一致连续低于$H^{3/4}(R)$。反例是通过用三次NLS方程近似五阶mKdV方程得到的。
We prove a first stability result of self-similar blow-up for the modified KdV equation on the line. More precisely, given a self-similar solution and a sufficiently small regular profile, there is a unique global solution which behaves at t tends to 0 as the sum of the self-similar solution and the smooth perturbation.
The initial-boundary value problem (ibvp) for the $m$-th order dispersion Korteweg-de Vries (KdV) equation on the half-line with rough data and solution in restricted Bourgain spaces is studied using the Fokas Unified Transform Method (UTM). Thus, this work advances the implementation of the Fokas method, used earlier for the KdV on the half-line with smooth data and solution in the classical Hadamard space, consisting of function that are continuous in time and Sobolev in the spatial variable, to the more general Bourgain spaces framework of dispersive equations with rough data on the half-li…
