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Questions about partial differential equations of elliptic type. Often used in combination with the top-level tag ap.analysis-of-pdes.
8
votes
2
answers
2k
views
Why don't we study hyperbolic equations as elliptic and parabolic equations?
In the research of elliptic and parabolic equations, the Schauder estimate is one of the most important issues for them. In this topic, we always bound the norm of higher regularity in the small bal …
5
votes
2
answers
1k
views
How to prove the second Korn inequality?
$\textbf{Theorem}.1$ (The first Korn inequality) Suppose that $ \Omega $ is a bounded domain in $ \mathbb{R}^d $ with Lipschitz boundary. Then\
\begin{eqnarray}
\sqrt{2}\left\|\triangledown u\right\| …
4
votes
1
answer
320
views
The behavior of $ \nabla u $ on the boundary for Poisson equations
Let $ \Omega $ be a bounded domain with smooth boundary. Consider the Poisson equation
\begin{eqnarray}
-\Delta u&=&f\text{ in }\Omega\\
u&=&0\text{ on }\partial\Omega
\end{eqnarray}
where $ f\in C_0^ …
4
votes
0
answers
126
views
A question of the book "Regularity Theory for elliptic PDE"
In the book "Regularity Theory for elliptic PDE", written by Fernández-Real, page 67, $ \tilde{u}_{k} $ converge to $ \tilde{u} $ only in $ C^1 $ norm, but the result is that we can get a equation for …
3
votes
1
answer
228
views
Schauder estimates with boundary conditions
For the elliptic equation with non-divergence form
$$
\sum_{i,j=1}^na_{ij}(x)\partial_{ij}^2u=f\text{ in }B(0,1)\quad\text{and}\quad u=g\text{ on }\partial B(0,1),
$$
where $ \{a_{ij}(x)\} $ is a matr …
2
votes
0
answers
74
views
The Green function for elliptic systems in two dimensions
I am reading some papers on Green functions of elliptic equations. Here the elliptic systems is stated as $ Lu=-\operatorname{div}(A\nabla u) $ where $ A(y)=(a_{ij}^{\alpha\beta}(y)) $ is a matrix val …
2
votes
0
answers
117
views
Some problems about energy estimates of elliptic equation
Recently I am reading a book of elliptic equations. In the beginning there is a famous Caccioppli inequality for weak solutions. The theorem is stated as follows
Suppose that $ u\in H^1(B(0,1)) $ sat …
2
votes
0
answers
312
views
Caccioppoli inequality in $ \mathbb{R}^2 $
Let $ \Omega\subset\mathbb{R}^d $ be a Lipschitz domain and $ A=(a_{ij}(y)):\Omega\to\mathbb{R}^{d\times d} $ be a matrix valued function with uniformly elliptic conditions i.e. $ \lambda|\xi|^2\leq a …
2
votes
0
answers
77
views
$ \varepsilon $-regularity, harmonic maps vs harmonic heat flow
Let $ \Omega\subset\mathbb{R}^n $ be a bounded domain with smooth boundary and $ (N,h)\subset\mathbb{R}^L $ is a smooth compact Riemannian manifold. Consider the local minimizer $ u\in W^{1,2}(\Omega, …
1
vote
0
answers
80
views
Boundary estimates for elliptic systems
Let $ \Omega\subset\mathbb{R}^d $ is a $ C^{1,\eta} $ domian with $ 0<\eta<1 $. Assume that $ A(y)=(a_{ij}^{\alpha\beta}(y)) $ is a matrix valued function, where $ 1\leq i,j\leq d $ and $ 1\leq\alpha, …
1
vote
0
answers
53
views
What is the the "method of ascending" in the study of elliptic systems in dimension two?
I have read a paper of Z. Shen [1]. In the paper the author mentioned we can deal with two-dimensional elliptic systems by adding a dummy variable (the method of ascending) and use the results on the …
1
vote
0
answers
71
views
Elliptic systems with two dimensions
Let $ \Omega\subset\mathbb{R}^2 $ is a $ C^{1,\eta} $ domian with $ 0<\eta<1 $. Assume that $ A(y)=(a_{ij}^{\alpha\beta}(y)) $ is a matrix valued function, where $ 1\leq i,j\leq 2 $ and $ 1\leq\alpha, …
1
vote
1
answer
148
views
Is the Poisson formula valid when the boundary condition is $ L^2 $?
Dirichlet problem for Laplace equation as follows
\begin{eqnarray}
\Delta{u}&=&0\text{ in }B_r(0)\\
u&=&g\text{ on }\partial B_{r}(0),
\end{eqnarray}
where $ g $ is continuous.
It is already known t …
1
vote
1
answer
153
views
How to show that $ u $ is vanishing in $ \mathbb{R}^3\setminus B_1 $?
I come across an interesting question.
Let $ B_r=\{x\in\mathbb{R}^3:|x|\leq r\} $ be the ball in $ \mathbb{R}^3 $ with radius $ r $. Assume that $ u \in C(\mathbb{R}^3\setminus B_1) $ satisfies
$$
\D …
1
vote
0
answers
490
views
How to deal with the boundary estimate for the Schauder estimates of laplacian equations?
Recently, I am learning Schauder estimates for elliptic equations and I come across a proposition as follows
Let $ \alpha\in (0,1) $ and $ \Omega $ be a bounded $ C^2(\Omega) $ domain on $ \mathbb{R} …