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Partial differential equations (PDEs): Existence and uniqueness, regularity, boundary conditions, linear and non-linear operators, stability, soliton theory, integrable PDEs, conservation laws, qualitative dynamics.

3 votes
1 answer
166 views

Strichartz estimates and Schrödinger equation with derivative

Let $$ iu_t + \Delta u = \Phi \cdot \nabla u$$ with initial data $u_0 \in H^s(\mathbb{R}^d)$ and $\Phi\colon \mathbb{R}^d \rightarrow \mathbb{R}^d$ sufficiently regular. Suppose I want to use Strichar …
Jakob Möller's user avatar
1 vote
0 answers
118 views

Estimate of a product of functions where $1/p + 1/q >1$

I have the following problem. I need to estimate the following quantity: $$|\nabla|^{-1}A u \nabla u \label{1}\tag{$*$}$$ I know that $A\in L^6(B_R)$, $u \in L^{14/5}\cap L^2(B_R)$ and $\nabla u \in L …
Jakob Möller's user avatar
1 vote
0 answers
50 views

Strong convergence from elliptic equation

Consider the following equation $$ \Delta A_n = -2\Im(\bar{u}_n(\nabla -iA_n)u_n) =: -J(u_n,A_n)$$ and suppose that $u_n \in L^{\infty}(I,H^1(\Omega))$ for some bounded $I\subset \mathbb{R}$, $\Omega\ …
Jakob Möller's user avatar
1 vote
0 answers
87 views

Reference for an application of J. Simon "Compact sets in the space $L^p(0,T;B)$"

Theorem 5 p.84 of J. Simons paper "Compact sets in the space $L^p(0,T;B)$" states a generalization of the Aubin-Lions lemma which relaxes the required regularity in time to the existence of a modulus …
Jakob Möller's user avatar
1 vote
1 answer
86 views

Why is this Hamiltonian flow of the Vlasov equation well defined?

Lions and Paul claim in their 1993 paper "Sur les mesures de Wigner" that the Hamiltonian flow $$\dot{x} = \xi, \quad \dot{\xi} = - \nabla V(x) $$ of the Vlasov equation $$\partial_t f + \xi \cdot \na …
Jakob Möller's user avatar
2 votes
Accepted

Why is this Hamiltonian flow of the Vlasov equation well defined?

I have found an answer. The condition $V\in C^{1,1}$ ensures that $\nabla V$ is Lipschitz which implies the existence of a global solution in the neighborhood of every point for the Cauchy problem of …
Jakob Möller's user avatar
2 votes
0 answers
112 views

Behavior at infinity of an $L^2$ function with $L^2$ mixed second derivatives

If $f$, $\nabla_x \cdot \nabla_y f \in L^2(\mathbb{R}^d_x\times \mathbb{R}^d_y)$, what can be said about decay at infinity of $\nabla_x f$, $\nabla_y f$? It is clear that $(\nabla_x^2 + \nabla_y^2) f …
Jakob Möller's user avatar
1 vote
0 answers
88 views

Reference request: PDE of the form $(\Delta - |u|^2)f = F(u)$

I am interested in equations of the form $$(\Delta -|u|^2)f = F(u)$$ where $F$ depends on $u$ and preferably on its derivative, too. $u$ is supposed to be given and $f$ the unknown. More precisely I a …
Jakob Möller's user avatar
2 votes
2 answers
239 views

Why is this estimate about Besov norms true

For reference, I am reading the paper "Uniqueness of Finite Energy Solutions for Maxwell-Dirac and Maxwell-Klein-Gordon Equations" by Masmoudi and Nakanishi. Let $A_0$ be a scalar function satisfying …
Jakob Möller's user avatar
4 votes
1 answer
102 views

Gauge fixing for a semi-relativistic model involving electromagnetism

When studying non-relativistic charged particles in an electromagnetic field with self-interaction on usually relies on the Schrödinger-Maxwell system \begin{align} i\partial_t u = -(\nabla-iA)^2 u + …
Jakob Möller's user avatar
2 votes
1 answer
203 views

Estimates for an elliptic PDE

Let's say I have an equation of the form $\Delta A = J$ where $J=u\nabla u + A|u|^2$ (Clarification: We are on $\mathbb{R}^3$ and $u$ is assumed to be in $H^1(\mathbb{R}^3)$). Then I could simply infe …
Jakob Möller's user avatar