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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.

4 votes
Accepted

Implicit function theorem for elliptic partial differential equations

As your title indicates, you would do this using the implicit function theorem for Banach space applied to an appropriately defined functional. This in turn requires proving that there is a bounded ri …
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1 vote

Variational problems whose lagrangian density depends on derivatives higher than 1.

You might find it helpful to study previous work on specific functionals like this. I suggest searching for journal articles that talk about extremal Kahler metrics (which usually means studying the i …
Deane Yang's user avatar
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1 vote

Divergence form Elliptic PDE Removable Singularity/Regularity Question

With a linear elliptic PDE, there's no way to bootstrap. What you see is what you get. The regularity of $A^{ij}\partial_j u$ cannot be made any better than the regularity of $g^i$. So if all you assu …
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1 vote

Hölder estimates on solutions of non-linear elliptic PDE.

I just stumbled onto this: On fully nonlinear elliptic equations of second order by Louis Nirenberg which seems to answer your question in the affirmative. Also, are you really studying a general f …
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1 vote

The Monge- Ampère equation with a non positive right hand side

In general nothing is known. Only local solvability is known for some special cases.
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5 votes
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Principal symbol for non-linear differential operators

I've seen only the first. It is indeed used mostly for identifying whether a nonlinear PDE is elliptic, hyperbolic, or parabolic. If so, one can use the respective linear theory, along with the approp …
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8 votes

Fundamental solution of an elliptic PDE in divergence form with non-symmetric matrix

If you assume that the coefficients $a^{ij}$ are smooth functions and let $$b^{ij} = \frac{1}{2}(a^{ij} + a^{ji}),$$ then the PDE can be written as $$ b^{ij}\partial^2_{ij}u + \partial_ia^{ij}\partial …
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2 votes

Elliptic theory on compact manifolds

Previous answer replaced by new one: Fix a finite relatively open cover $U_1, \dots, U_m$ of $M$, where each $U_i$ is diffeomorphic to either the open ball or the half-ball obtained by intersecting …
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6 votes
Accepted

Reference for $\epsilon$-regularity

First, it is straightforward to adapt Haslhofer's proof to higher dimensions, using the Sobolev inequality: For any compactly supported $u$ such that $\|\nabla u\|_2 < \infty$, $$ \|u\|_{\frac{2n}{n-2 …
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7 votes

Green's operator of elliptic differential operator

Start with the linear problem: Let $K \subset \Gamma(E)$ denote the kernel of $P$ and $\hat{K} \subset \Gamma(F)$ the cokernel. Assume that there are inner products on the vector bundles $E$ and $F$ a …
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1 vote

The adjoint operators as elliptic operators

Any Lie bracket structure that is a first order differential operator is, by bilinearity and skew-symmetry, of the form $$ \mathrm{ad}_X Y = A^{kp}_{ij}(X^i\partial_pY^j- Y^i\partial_pX^j)e_k, $$ wher …
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2 votes

BVPs for elliptic PDOs: When do Green functions ($L^2$ inverses) define pseudo-differential ...

Assuming that $P^{-1}$ is a right inverse and $\Omega$ an open subset of $\mathbb{R}^n$ or an open manifold, then you can proceed as follows: 1) An operator $Q: L^2(\Omega) \rightarrow L^2\Omega$ is …
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3 votes
Accepted

Elliptic regularity of harmonic forms in $L^1$

Let me turn my comment into a general discussion for which a special case is an answer to your question. First, on an open domain $D \subset \mathbb{R}^n$, there is a standard elliptic regularity res …
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11 votes
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Elliptic regularity on compact manifold without boundary

This follows from the following regularity estimate for the flat Laplacian case (which is, I believe, proved in Warner's book using Fourier series on a torus but also in most standard texts on ellipti …
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8 votes
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Elliptic regularity on manifolds: Is this true?

Use a partition of unity to reduce the statement to a local one for a function compactly supported on a coordinate chart. At that point, any elliptic regularity theorem on an open domain in Rn can be …
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