Aleksandrov-Bakelman-Pucci estimates: Difference between revisions
imported>Nestor mNo edit summary |
imported>Nestor mNo edit summary |
||
| Line 5: | Line 5: | ||
Let $u$ be a viscosity supersolution of the linear equation: | Let $u$ be a viscosity supersolution of the linear equation: | ||
\[ | \[ a_{ij}(x) u_{ij}(x) \leq f(x) \;\; x \in B_1\] | ||
\[ u \leq 0 \;\; x \in \partial B_1\] | \[ u \leq 0 \;\; x \in \partial B_1\] | ||
where the coefficients $a_ij(x)$ are only assumed to be measurable functions such that for positive constants $\lambda<\Lambda$ we have | where the coefficients $a_ij(x)$ are only assumed to be measurable functions such that for positive constants $\lambda<\Lambda$ we have | ||
\[ \lambda |\xi|^2 \leq | \[ \lambda |\xi|^2 \leq a_{ij}(x) \xi_i\xi_j \leq \Lambda |\xi|^2 \;\;\forall \xi \in \mathbb{R}^n \] | ||
Then, | Then, | ||
Revision as of 17:21, 3 June 2011
The celebrated "Alexandroff-Bakelman-Pucci Maximum Principle (often abbreviated often as "ABP Estimate") is a pointwise estimate for weak solutions of elliptic equations. It is a fundamental result which is the backbone of the regularity theory of fully nonlinear second order elliptic equations (reference Caffarelli-Cabré) and more recently for Fully nonlinear integro-differential equations (reference Caffarelli-Silvestre).
The classical Alexsandroff-Bakelman-Pucci Theorem
Let $u$ be a viscosity supersolution of the linear equation:
\[ a_{ij}(x) u_{ij}(x) \leq f(x) \;\; x \in B_1\] \[ u \leq 0 \;\; x \in \partial B_1\]
where the coefficients $a_ij(x)$ are only assumed to be measurable functions such that for positive constants $\lambda<\Lambda$ we have
\[ \lambda |\xi|^2 \leq a_{ij}(x) \xi_i\xi_j \leq \Lambda |\xi|^2 \;\;\forall \xi \in \mathbb{R}^n \]
Then,
\[ \sup \limits_{B_1}\; u^n \leq C_{n,\lambda,\Lambda} \int_{\{ u=\Gamma_u \} } f_+^n dx \]