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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.

12 votes
4 answers
2k views

History of ODE and PDE reference request

Is there any reference (book or articles) which made the history (up to the modern times) and the conceptual development of Ordinary Differential Equations and Partial Differential Equations? It will …
Bogdan's user avatar
  • 1,759
7 votes
1 answer
555 views

Sobolev spaces are smooth? Their dual is strictly convex?

Do you know any reference which says something about the: Smoothness of the Sobolev space $W^{1,p}(\Omega)$ i.e. if the duality mapping $J\colon W^{1,p}(\Omega)\to W^{1,p}(\Omega)^*$ is a singleton. …
Bogdan's user avatar
  • 1,759
6 votes
1 answer
216 views

Question about Bochner measurability

When I study parabolic pde's I often came across the following type of Bochner spaces $L^p([a,b];L^{q}(\Omega),\ W^{1,p}([a,b];L^{q}(\Omega))$ and $L^{q}([a,b];W^{1,p}(\Omega))$ where $p,q\geq 1$ and …
Bogdan's user avatar
  • 1,759
4 votes
1 answer
255 views

Reaction-diffusion systems treated as dynamical systems

I wonder if there is a good reference on reaction-diffusion systems on $\mathbb{R}^N$, that treats them as dynamical systems. I have the books of Alain Haraux – Systèmes dynamiques dissipatifs et appl …
Bogdan's user avatar
  • 1,759
4 votes
0 answers
706 views

Maximum Principles in Parabolic PDE with Neumann Condition

I am looking for some maximum principles and comparison results for parabolic equations. The most complete book I've found on this subject is: Murray Protter, Hans Weinberger - Maximum Principles in D …
Bogdan's user avatar
  • 1,759
4 votes
0 answers
106 views

The logistic elliptic equation

Studying the Fisher-KPP evolution equation I came across the steady state elliptic problem which can be written in the following form: $$ \begin{cases} -d\Delta Y(x)=r(x)Y(x)\left (1-\dfrac{Y(x)}{K(x) …
Bogdan's user avatar
  • 1,759
4 votes
1 answer
360 views

Strong positivity of Neumann Laplacian

There are many places in the literature where the positivity of some semigroups is treated. However I did not know anyone which states and proves the strong positivity even for the basic semigroups li …
Bogdan's user avatar
  • 1,759
4 votes
1 answer
237 views

When is $W^{1,p}(\Omega)$ a Banach algebra?

Let $\Omega \subseteq \mathbb{R}^d$ be bounded and open with $\partial\Omega$ Lipschitz, $1<p<\infty$. My question: knowing that $f,g\in W^{1,p}(\Omega)$ for what $p$ can we conclude that $f\cdot g\in …
Bogdan's user avatar
  • 1,759
4 votes
3 answers
271 views

Intriguing simple question about Sobolev space $W^{1,p}(\Omega)$

Let $w_1,w_2\in W^{1,p}(\Omega)$ be two functions with $w_1,w_2>0$ and $\dfrac{w_2}{w_1},\dfrac{w_1}{w_2}\in L^{\infty}(\Omega)$, where $\Omega\subset\mathbb{R}^N$ is a bounded domain (i.e. open and c …
Bogdan's user avatar
  • 1,759
4 votes
1 answer
450 views

Contractivity of Neumann Laplacian

I have an intriguing and probably simple question: reading the articles and books of Wolfgang Arendt on semigroups of linear operators, I found on many places properties of the Neumann Laplacian. In …
Bogdan's user avatar
  • 1,759
3 votes
1 answer
383 views

Neumann/Robin Laplacian semigroup well-known estimate

Let $\Delta_R:D(\Delta_R)\to L^2(\Omega)$ the Robin Laplacian defined on: $$D(\Delta_R)=\left\{u\in H^1(\Omega)\ \big |\ \Delta u\in L^2(\Omega),\ \dfrac{\partial u}{\partial\nu}+bu=0 \ \text{on}\ \pa …
Bogdan's user avatar
  • 1,759
3 votes
0 answers
101 views

A special type of differential equations

Working in optimal control of PDEs, I came across a type of evolution problem that has instead of an initial condition a link between the initial state and the final state. Here is a simplified versio …
Bogdan's user avatar
  • 1,759
3 votes
1 answer
278 views

Are Neumann Laplacian eigenfunctions in $C(\overline{\Omega})$?

Consider that $u\in H^1(\Omega)$ with $\Delta u\in L^2(\Omega)$ (in the distributional sense) such that for some $\lambda>0$ we have that: $$\begin{cases} \Delta u(x)=\lambda u(x), & x\in\Omega\\ \dfr …
Bogdan's user avatar
  • 1,759
3 votes
1 answer
253 views

$L^{\infty}$ estimate for heat equation with $L^2$ initial data

Is there a way to show in a relatively simple manner that for a Lipschitz bounded, connected, open domain $\Omega\subset\mathbb{R}^N$ for any $f\in L^2(\Omega)$ the solution of the problem: $$\begin{c …
Bogdan's user avatar
  • 1,759
3 votes
1 answer
163 views

Question about Lebesgue Bochner spaces

Let $T>0$ and $\Omega\subset\mathbb{R}^N$ be a bounded domain. Also $p\in (1,\infty)$ is any number. I know that $u\in L^{p}((0,T);L^p(\Omega))$ and $\nabla u\in L^{p}((0,T);L^p(\Omega))^N$. How can I …
Bogdan's user avatar
  • 1,759

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