Logarithmic Caccioppoli inequality (source code)

= Logarithmic Caccioppoli inequality
{c}

For a positive weak supersolution $u$ of a uniformly elliptic divergence-form equation, testing with $\eta^2/u$ gives
$$
\int\eta^2|D\log u|^2\leq C\int|D\eta|^2.
$$
The constant depends only on the ellipticity bounds.