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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
1 answer
412 views

Simplicity of eigenvalues of an elliptic operator under a symmetry assumption

A striking difference in the spectral analysis of 2nd order elliptic boundary-value problems between one and several space dimensions is the following. In one space dimension, the eigenvalues are simp …
Denis Serre's user avatar
  • 52.3k
9 votes
1 answer
205 views

Geometry of the positive definite cone, versus homogenization of elliptic PDEs

Homogenization is a process that assigns to a positive definite-valued map $x\mapsto S(x)$ a non-trivial but physically meaningful average $\bar S$. There are various settings, for instance stochastic …
Denis Serre's user avatar
  • 52.3k
5 votes
1 answer
163 views

Reinforced Maximum Principle

Let $U\subset{\mathbb R}^n$ be a bounded open domain with smooth boundary. I assume that $U$ is diffeomorphic to a ball. You may think of $L=\Delta$ and $U$ is the unit ball. Let $L=\operatorname{div} …
Denis Serre's user avatar
  • 52.3k
7 votes
1 answer
385 views

Convex solutions of the Poisson equation

Let $D$ be a planar, bounded, convex open domain. Given a positive function $f:D\to(0,+\infty)$, let us consider the Poisson equation $$\Delta u=f\quad\hbox{in }D.$$ Not specifying any boundary condit …
Denis Serre's user avatar
  • 52.3k