Skip to main content
Search type Search syntax
Tags [tag]
Exact "words here"
Author user:1234
user:me (yours)
Score score:3 (3+)
score:0 (none)
Answers answers:3 (3+)
answers:0 (none)
isaccepted:yes
hasaccepted:no
inquestion:1234
Views views:250
Code code:"if (foo != bar)"
Sections title:apples
body:"apples oranges"
URL url:"*.example.com"
Saves in:saves
Status closed:yes
duplicate:no
migrated:no
wiki:no
Types is:question
is:answer
Exclude -[tag]
-apples
For more details on advanced search visit our help page
Results tagged with
Search options answers only not deleted user 85906

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

1 vote
Accepted

Is $H_0^1$ a redundant assumption in the 2D Agmon inequality?

There is probably a regularity assumption on $\Omega$ in the lecture notes, right? Zero traces are very convenient in such proofs because then $\Omega$ may be very irregular and one may rely on resu …
Hannes's user avatar
  • 2,670
4 votes
Accepted

$W^{1,p}$ ($1\le p<2$) uniqueness of elliptic equations

The answer is yes if and only if you have optimal elliptic regularity in $W^{-1,p'}(B)$ for some $p>2$ for the adjoint differential operator, i.e., the one given by the transpose matrix $A^\top$. Cons …
Hannes's user avatar
  • 2,670
3 votes
Accepted

Is there any "extra regularity" to the solution to Poisson's equation posed on a 3-dimension...

As discussed in the comments, such a result can be found in Jochmann's "An $H^s$-Regularity Result for the Gradient of Solutions to Elliptic Equations with Mixed Boundary Conditions".
Hannes's user avatar
  • 2,670
2 votes
Accepted

Parabolic Regularity with Neumann B.C

Let's see how this goes. First, let me say that the continuity estimate you are looking for is contained in [3, Theorem 4.5] under the integrabilities as I had already mentioned, so $q > n$ and $p > 2 …
Hannes's user avatar
  • 2,670
4 votes
Accepted

Question on Sobolev spaces in domains with boundary

For the sake of completeness, an expansion on the comment by Mike Miller: In Evans/Gariepy, Thm. 4.3.1, it is proven that if the boundary of $\Omega$ is Lipschitz, then for $1 \leq p < \infty$ there …
Hannes's user avatar
  • 2,670
3 votes

Higher regularity of solutions for Laplace equation with mixed boundary condition

This is more of an extended comment, but maybe it is helpful. At least for the case of mixed boundary conditions involving Dirichlet and Neumann conditions where the corresponding boundary parts actu …
Hannes's user avatar
  • 2,670
1 vote
Accepted

Showing existence of minimisers with single integral constraint on a possibly non-Lipschitz ...

Your domain is a Lipschitz (graph) domain. The 3-dimensional (!) Lebesgue measure of $\mathcal{F}$ is indeed zero, whereas $\mathcal{F}$ has positive measure for the boundary measure $\sigma$ (which c …
Hannes's user avatar
  • 2,670
2 votes

Trace of a function

The spatial evaluation (or trace) operator $\mathrm{tr}_L$ at $L$ is well defined and continuous on $H^s(0,L)$ for $s>1/2$; a classic reference is [LM, Chapter 1.9]. (Of course the range $s>1/2$ is ex …
Hannes's user avatar
  • 2,670
4 votes
Accepted

Gagliardo-Nirenberg inequality for bounded domain

If you assume that $\Omega$ is a bounded uniform extension domain, then your desired inequality holds true. By uniform extension domain, I mean that there exists a linear extension operator $E$ which …
Hannes's user avatar
  • 2,670
1 vote
Accepted

Solution of hyperbolic equations with $V^*$ data

Chapter 9 in Volume 1 of Lions/Magenes [1] treats this case, even for nonautonomous operators. One essentially gets (somewhat as expected?) a regularity shift just in the spatial components, so the so …
Hannes's user avatar
  • 2,670
1 vote
Accepted

Optimal control theory of PDEs

Maybe most obviously, there is a whole area of research devoted to numerical analysis of optimal control problems where results like $\|\bar f - f_h\| \in O(h^\alpha)$ as $h \searrow 0$ are of interes …
Hannes's user avatar
  • 2,670
5 votes
Accepted

Reference request: Uniformly elliptic partial differential operator generates positivity pre...

Check Chapter 4, more specifically Chapter 4.2 in Ouhabaz: Analysis of heat equations on domains (2005). ZBL1082.35003. The approach there goes by the form method which I personally perceive to be ver …
Hannes's user avatar
  • 2,670
2 votes

Existence of an extension operator $E: W_0^{s,p}(\Omega)\rightarrow W^{s,p}(\mathbb{R}^d)$?

This is a somewhat delicate topic and I think what has been proposed so far did not capture fully what is going on. (Probably I am missing something, too, and I also did not fully answer OP's question …
Hannes's user avatar
  • 2,670
5 votes
Accepted

Question about Lebesgue Bochner spaces

By Pettis' theorem, $u \colon (0,T) \to W^{1,p}(\Omega)$ is strongly [Bochner] measurable if and only if it is weakly measurable due to separability of $W^{1,p}(\Omega)$. It is thus sufficient to show …
Hannes's user avatar
  • 2,670
1 vote
Accepted

An inequality from Bessel potential space to Besov space

I think that your idea is completely correct, but the choice of $s$ and $q$ is indeed somewhat curious in the paper. However, the case $q=p$ should be sufficient for the proof to work: We need $s$ an …
Hannes's user avatar
  • 2,670

15 30 50 per page